Early Metallurgy of the Persian Gulf: Technology, Trade, and the Bronze Age World 0391042130, 9780391042131

Table of contents :
Contents
Foreword
Preface
Acknowledgments
List of Figures
List of Tables
1 Introduction
Outline and Genesis of the Project
Copper Production and the Bronze Age Economy of Southeastern Arabia
Alloying Practices in Bronze Age Southeastern Arabia
Investigation of the Bronze Age Tin Trade
Analytical Techniques
Outline of Chapters
2 Geology and Early Exploitation of Copper Deposits in Southeastern Arabia
Geology of Northern Oman and Masirah
Copper Deposits in Southeastern Arabia
Early Research into Ancient Copper Production in the Oman Peninsula
German Mining Museum Project in Oman
Periodicity in Copper Production in Prehistoric Southeastern Arabia
Organization of Early Copper Production
Copper-Base Objects in Bronze Age Southeastern Arabia
Summary
3 Analyzed Artifacts: Contexts and Chronology
AI Sufouh
Unar1
Unar2
Tell Abraq
4 Results of Compositional Analyses
Introduction
Elemental Concentrations
Elemental Relationships: Rank-Correlation Analyses
Principal Components Analyses (PCA)
Summary
5 Discussion of Compositional Results
Introduction
Iron and Sulfur
Arsenic, Nickel and Cobalt
Tin-Bronze
Alloy Use in Different Object Categories
Summary
6 Lead Isotope Analysis in Archaeology
Theoretical Basis of the Lead Isotope Technique
LIA in Archaeology
Issues for Archaeological LIA in the Gulf Region
Summary
7 Lead Isotope Data from the Gulf
Introduction
Radiogenic Outliers in the Analyzed Umm al-Nar Period Objects
Isotopic Differences by Site
Differences by Composition (Alloy Group)
Isotopic Comparisons with Bronze Age Objects from the Gulf
Absolute Provenance
Tin-Bronze in Wider Western Asia: Important Lead Isotope Studies
LIA: Summary of the Main Findings
8 Tin and Tin-Bronze in Early Western Asia
Introduction
Tin Deposits in Western Asia and Surrounding Regions
Archaeological Evidence for Early Tin-Bronzes
Texts Referring to the Bronze Age Use and Trade of Tin
Summary of Archaeological, Geological and Textual Evidence
Tin-Bronze in the Gulf: Patterns of Acquisition
Reconsidering the "Tin Problem"
9 Summary and Conclusions
Aims Reiterated
Summary of Major Results
Prospects for Future Research
Appendix
Analytical Techniques and Data Treatment
References
Index
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D
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Citation preview

EARLYMETALLURGY OF THE PERSIAN GULF Technology, Trade, and the Bronze Age World

A M E R I C A N S C H O O L OF PREHISTORIC RESEARCH M O N O G R A P H SERIES

Series Editors

C. C. L A M B E R G - K A R L O VSKY, Harvard University DAVID PILBEAM, Harvard University OFE R BAR-YOSEF, Harvard University Editorial Board STE V E N L. K U H N , University of Arizona, Tucson D A N I E L E. LIEBE R M AN, Harvard University R I C H A R D H. M E A D 0 W, Harvard University M A R Y M. V O I G T , The College of William & Mary H E N R Y T. W R I G H T , University of Michigan, A n n Arbor Production Editor W R E N F 0 U R N I ER, Harvard University

The American School of Prehistoric Research (ASPR) Monographs in Archaeology and Paleoanthropology present a series of documents covering a variety of subjects in the archaeology of the Old World (Eurasia, Africa, Australia, and Oceania). This series encompasses a broad range of subjects-from the early prehistory to the Neolithic Revolution in the Old World, and beyond including: hunter-gatherers to complex societies; the rise of agriculture; the emergence of urban societies; human physical morphology, evolution and adaptation, as well as; various technologies such as metallurgy, pottery production, tool making, and shelter construction. Additionally, the subjects of symbolism, religion, and art will be presented within the context of archaeological studies including mortuary practices and rock art. Volumes may be authored by one investigator, a team of investigators, or may be an edited collection of shorter articles by a number of different specialists working on related topics.

Technology, Trade, and the Bronze Age World

Lloyd R. Weeks

Brill Academic Publishers, Inc. Boston Leiden 2003

Library of Congress Cataloging-in-Publication Data

Weeks, Lloyd R., 1970Early metallurgy of the Persian Gulf : technology, trade, and the Bronze Age World 1 Lloyd R. Weeks. p. cm. - (American school of prehistoric research monograph series ;vol. 2) Includes bibliographical references and index. ISBN 0-391-04213-0 1. Bronze age-Persian Gulf. 2. Metal-work, Prehistoric-Persian Gulf. 3. Mines and mineral resources, Prehistoric-Persian Gulf. 4. Excavations-(Archaeology)-Persian Gulf. 5. Bronze-Persian Gulf-Metallurgy. 6. Tin bronze-Persian Gulf. 7. Persian Gulf-Antiquities. I. Title. 11. Series.

ISSN 1543-0529 ISBN 0-391-04213-0 O Copyright 2004 by Brill Academic Publishers, Inc., Boston

All rights reserved. No part of this publication may be reproduced, translated, stored in a retrieval system, or transmitted in any form or by any means, electronic, mechanical, photocopying, recording or otherwise, without prior written permission from the publisher.

Authorization to photocopy item for internal or personal use is granted by Brill provided that the appropriate fees are paid directly to The Copyright Clearance Center, 222 Rosewood Drive, Suite 910 Danvers MA 01923, USA. Fees are subject to change.

PRINTED IN THE UNITED STATES OF AMERICA

Contents

Foreword vii Preface ix Acknowledgments xi List of Figures xiii List of Tables xvii lntroduction 1 Outline and Genesis of the Project

1

Copper Production and the Bronze Age Economy of Southeastern Arabia

4

Alloying Practices in Bronze Age SoutheasternArabia 5 Investigation of the Bronze Age Tin Trade 5 Analytical Techniques 6 Outline of Chapters 6

Geology and Early Exploitationof Copper Deposits in Southeastern Arabia

7

Geology of Northern Oman and Masirah

7

Copper Deposits in Southeastern Arabia

12

Early Research into Ancient Copper Production in the Oman Peninsula

14

German Mining Museum Project in Oman

22 Periodicity in Copper Production in Prehistoric Southeastern Arabia

33

Organization of Early Copper Production

43

Copper-Base Objects in Bronze Age Southeastern Arabia Summary

54 57

Analyzed Artifacts: Contexts and Chronology AI Sufouh Unarl

61

Unar2

63

59

59

Tell Abraq

64

Results of CompositionalAnalyses lntroduction

71

71

Elemental Concentrations

73

Elemental Relationships: Rank-CorrelationAnalyses Principal Components Analyses (PCA) Summary

Discussion of Compositional Results lntroduction

105

Arsenic, Nickel and Cobalt

109

121

Alloy Use in Different Object Categories Summary

105

105

Iron and Sulfur Tin-Bronze

99

102

127

124

96

Lead lsotope Analysis in Archaeology

129

Theoretical Basis of the Lead lsotope Technique LIA in Archaeology

129

131

Issues for Archaeological LIA in the Gulf Region Summary

134

143

Lead lsotope Data from the Gulf (L. R. Weeks and K. D. Collerson) lntroduction

145

145

Radiogenic Outliers in the Analyzed Umm al-Nar Period Objects

145

Isotopic Differences by Site

147

Differences by Composition (Alloy Group) 150 lsotopic Comparisons with Bronze Age Objects from the Gulf

152

Absolute Provenance

155

Tin-Bronze in Wider Western Asia: Important Lead lsotope Studies

160

LIA: Summary of the Main Findings

163

Tin and Tin-Bronze in Early Western Asia lntroduction

165

l65

Tin Deposits in Western Asia and Surrounding Regions 166 Archaeological Evidence for Early Tin-Bronzes

173

Texts Referringto the Bronze Age Use and Trade ofTin Summary of Archaeological, Geological and Textual Evidence

180

Tin-Bronze in the Gulf: Patterns of Acquisition Reconsidering the "Tin Problem"

Summary and Conclusions Aims Reiterated

197

Summary of Major Results

l98 200

Prospects for Future Research

Appendix Analytical Techniques and Data Treatment

References 209 Index

247

187

197

203

181

178

Foreword

Mesopotamia, as has often been stated, lacked resources. Its lack of metal ores required this world of, at times, independent city-states and, at other times, empire, to look to distant lands in order to procure its metauores. Mesopotamian technology, however, was not a form of administrative or scribal concern. When it came to metal technology written texts offer limited information and are all but silent on the training, organization, and recruitment of metal smiths. Similarly, the texts are vague, or more typically silent, as to the geographical provenience from whence they obtained their metallore, its quantity, quality, price, or techniques of fabrication. It is left to the archaeologist and the recovered metal artifacts, workshops, associated tools, and mines, to address these questions. As important as the recovery of the metal object is its analysis. Analyses are especially helpful with regard to elucidating the sources of the metauore, the techniques of their manufacture, and the uses to which they were put. Recently there has been a trend in historical narrative to focus upon a given item and build upon it a regional, even global, history of the world. Thus, we have the history of the world according to spices, salt, cod-fish, homespun, maps, the banana and the potato, clocks, tobacco, and of course slaves, to mention but a few volumes that have produced a macrohistory according to a single item. Archaeologists have long been practitioners of such an approach. The study of metals, archaeometallurgy, has long had pride-of-place in such an approach. This monograph attests to the contribution of both archaeology and our arsenal of new analytical techniques in the study of metallurgy. Decades ago V. G. Childe placed metallurgy on the top of his list of important crafts. He maintained that the development of early civilizations was a consequence of the invention of metallurgy (Childe 1930). Bronze-working, he believed, encouraged the manufacture of tools, which in turn led to more productive agriculture, and the growth of cities. Seventyfive years ago, Childe (1930:39) could point out that "Other documents from Mesopotamia, also written in the wedge-like characters called cuneiform, refer to the importation of copper from the mountainous region east of the Tigris and of metal and stones from Magan (probably Oman on the Persian Gulf)". As demonstrated in this volume Childe's location of Magan as an important source of copper is shown to be entirely correct. In this volume Lloyd Weeks adds a significant chapter to our study of archaeometallurgy. His initial focus is the

vii

Arabian Peninsula where he introduces us to a new corpus of metal artifacts from the United Arab Emirates. Surprisingly, a significant percentage of these metals, recovered from the site of Tell Abraq, are tin-bronzes. Importantly, these artifacts, and others from near-by sites, are subject to Proton-Induced X-ray Emission analysis (PIXE). With these results in hand his horizon widens and takes on a review of metallurgy within the Bronze Age of the entirety of the Arabian Peninsula, where an extensive amount of archaeometallurgical work has been undertaken within the past few decades. Finally, his volume offers an up-to-date review of the enduring "tin-problem" within the context of the greater Near East. Again, Childe (1928:157) confronted the problem: "The Sumerians drew supplies of copper from Oman, from the Iranian Plateau, and even from Anatolia, but the source of their tin remains unknown". Today we have answers, even if they must still be regarded as partial ones. With a full appreciation of the complexity of interactions that characterized the third millennium throughout the Near East the author is not reticent to offer conclusions. Thus, he states that ". . . the absolute source of the metal [tin-bronze] is likely to have been far to the north and east in Afghanistan or central Asia". The central Asian source has been given reality by the recent discovery in Uzbekistan and Tadzhikistan of Bronze Age settlements and mines involved in tin production (Parzinger and Boroffka 2003). How is it then that if central Asian tin was reaching the Arabian Peninsula that there is a paucity, indeed a very great poverty, of contemporary tin-bronzes on the Iranian Plateau? The question does not allude the author. In fact, nothing within the data base, either bibliographic nor artifactual, escapes his lens. With careful attention to detail, a comprehensive appreciation of the evidence at hand, while subjecting the relevant evidence to laboratory analysis, Hercule Poirot would be in agreement that Lloyd Weeks' study adds both substantial evidence and clues that point toward an emerging solution of the century long case of the "tin-problem". Finally, thanks are due to Mr. Landon T. Clay whose generous support over the years include some of the metals analysis reported upon in this volume. C. C. Lamberg-Karlovsky

viii

Preface

This volume examines the production and exchange of copper and its alloys in the Bronze Age Persian Gulf. During the third and second millennia BCE, the Gulf was a critical long-distance trade route by which prestige goods such as lapis lazuli, carnelian and ivory reached wider western Asia. Additionally, the Gulf functioned as a major metal supply route for Mesopotamia and southwestern Iran, and abundant cuneiform sources testify to the flourishing copper trade between the urban centers of southern Mesopotamia and the Bronze Age Gulf polities of Dilmun and Magan. Multiple aspects of the Bronze Age Gulf trade network are investigated in this research program, which is based upon the archaeometallurgical analysis of copperalloy objects from four third millennium BCE sites in the United Arab Emirates. The data generated by compositional and lead isotope analyses are integrated with geological information from southeastern Arabia and technological studies of early copper smelting in the region, and provide important insights into a number of issues of archaeological significance. These range from technological aspects of early copper-base alloy production in southeastern Arabia, to more anthropologicallyinformed research regarding the interaction of specialized copper production, exchange, and social complexity in early Arabia. The broader archaeological issue of the Bronze Age tin trade is also investigated in detail. The trade in this metal linked vast areas of western Asia, from the IndoIranian borderlands to the Aegean, through a series of overland and maritime trade routes and exchange relationships that are only hazily understood. The discovery of tin and tin-bronze objects in third millennium BCE contexts in the U.A.E., demonstrated conclusively in the present volume, provides important new evidence for the discussion of the tin trade, a long-standing problem of Bronze Age western Asian archaeology.

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AcknowledgmentS

This book began its life as a doctoral dissertation undertaken at the University of Sydney, Australia. Although subsequent periods of research have resulted in the substantial reworking of the original text, as well as many additions, the ideas and approaches contained within it remain those which were shaped so strongly by my thesis supervisors, Dan Potts (University of Sydney) and Richard Thomas (University of Western Sydney). I would like to express my gratitude for their guidance during that critical and seemingly endless period, and in particular to Dan Potts for his practical and intellectual input into so many aspects of the work. My thesis was assessed by Andreas Hauptmann (Deutsches Bergbau-Museum, Bochum), Roger Moorey (Ashmolean Museum, Oxford), and Vincent Pigott (Institute of Archaeology, London), and this volume has been greatly improved by their constructive comments and criticisms. Of course, this volume has reached its present form since my arrival at the Peabody Museum and is funded through the good graces of the American School of Prehistoric Research (ASPR). I would like to sincerely thank the ASPR and in particular Karl Lamberg-Karlovsky and Ofer Bar-Yosef for the opportunity to produce this study, and for shepherding the manuscript when it threatened to stray. Great thanks must also be extended to Wren Fournier, who acted as production editor for the volume and oversaw all aspects of the editorial and production processes, including some particularly time-consuming adaptations of images. The volume is based upon a large number of material analyses, for which the assistance of numerous scholars and institutions must be acknowledged. The PIXE analyses were conducted by Grahame Bailey, Philip Johnson and Ed Stelcer at the Australian Nuclear Science and Technology Organisation, Lucas Heights, N.S.W., and Rainer Siegele provided important information on the accuracy and precision of the data. The TIMS lead isotope analyses of artifacts from Tell Abraq were conducted at the Department of Earth Sciences, University of Queensland, by Ken Collerson and Immo Wendt. The more recent MC-ICP-MS isotopic analyses of material from A1 Sufouh, Unarl, and Unar2 were also conducted at the University of

Queensland facilities under the direction of Ken Collerson, and were undertaken by Balz Kamber and Arildo Oliveira. I would like to express my gratitude t o all of these people for their diligence, and for taking the time to discuss various aspects of the analytical techniques and data for my enlightenment. Of course, analyses could never have proceeded without material to analyze. For allowing access to archaeological samples, I would particularly like to thank Sabah Jasim (Sharjah Archaeological Museum, U.A.E.), Christian Velde and Derek Kennet (Ras al-Khaimah Museum, U.A.E.), Hussein Qandil (Dubai Museum, U.A.E.), Dan Potts (Sydney University Excavations at Tell Abraq), and Jodie Benton (Sydney University Excavations at A1 Sufouh). A number of these scholars have also provided important unpublished contextual information on the samples, for which I am grateful. The volume benefited greatly from advice generously given during its formulation, and from editorial corrections. For general discussions regarding statistical approaches, and for confusing me by not thinking in the same way (apparently there is more than one), I would like to thank John Clegg (University of Sydney). Advice on the application of multivariate statistics to the PIXE data was kindly provided by Richard Wright (University of Sydney) and Peter Grave (University of New England). Large chunks of the volume were read and constructively commented upon by Peter Magee (Bryn Mawr College), Alastair Paterson (University of Western Australia) and Cameron Petrie (Somerville College, Oxford), a terrific help. The ideas that they read about benefited from wideranging archaeological discussions with Phi1 Kohl (Wellesley College), A. Bernard Knapp (University of Glasgow), and Mike Barbetti (University of Sydney). My doctoral research was financially supported by an Australian Commonwealth government Australian Postgraduate Award scholarship, three grants for PIXE analyses from the Australian Institute of Nuclear Science and Engineering (AINSE), a Carlyle Greenwell bequest for isotopic analyses of material from the United Arab Emirates, and a grant from the British School of Archaeology in Iraq (BSAI)for isotopic analyses of material from Saar, Bahrain. New isotopic analyses of objects from the U.A.E. presented in this volume were supported by a grant from the ASPR.

Finally, I would like to acknowledge my friends and family, who have been there for the duration. N o part of this work could have been completed without their support and it is therefore to them, individually and in their collective role as my personal safety net, that I owe my greatest thanks.

List of Figures

2.10 2.11 2.12 2.13 2.14 2.15 2.16 3.1 3.2 3.3 3.4 3.5 3.6 3.7 3.8 3.9 3.10

xiii

Major archaeological sites of the U.A.E. Geological units comprising the Oman Mountains Major copper deposits and metallurgical sites of southeastern Arabia Slag heaps at Samdah, Oman Slag fields at Tawi 'Arja, Oman Settlement at Maysar 1, the mining area M2, and the cemetery M3 Evidence for Umm al-Nar Period mining at Maysar 2, Oman Hammer and anvil stones from Maysar 1, Oman Fragments of the base of a smelting furnace from Maysar 1, Oman Slag typology for Umm al-Nar Period copper production at Maysar 1 Iron Age smelting remains from Oman Iron Age copper slag from 'Arja in Oman Periods of copper production in southeastern Arabia Slag-filled planoconvex copper ingot from Al-Aqir in Oman Hoard of planoconvex copper ingots found at Maysar 1 in House 4 Third millennium BCE copper-smelting settlement of Zahra 1, Oman Iron Age slag heap at Raki 2, Oman Chronology of the excavated tomb assemblages A1 Sufouh Tomb I after excavation (from west) Fragments of copper-base objects from A1 Sufouh analyzed in this study Unarl Umm al-Nar Period tomb Fragments of copper-base objects from Unarl analyzed in this study Unar2 tomb after excavation, showing chamber designations (from north) Fragments of copper-base objects from Unar2 analyzed in this study Tell Abraq tomb after excavation (from north) Two copper-base rings from the Tell Abraq tomb, as excavated in position on phalanges Copper-base objects from Tell Abraq analyzed in this study

4.17 Tin concentrations in all Urnm al-Nar Period objects analyzed by PIXE 4.1 8 Negative correlation between tin and cobalt in the Urnm al-Nar objects analyzed by PIXE 4.19 Arsenic and nickel in Urnm al-Nar Period objects analyzed by PIXE 4.20 Nickel and cobalt in the Urnm al-Nar Period objects analyzed by PIXE 4.21 Arsenic and cobalt in the Urnm al-Nar Period objects analyzed by PIXE 4.22 Tin and silver in the Urnm al-Nar Period objects analyzed by PIXE 4.23 Element Correlations as found in a PCA of the unmodified PIXE compositional data and PIXE data converted to rank-order 4.24 PCA scattergram of untransformed PIXE data for objects from Tell Abraq and A1 Sufouh 4.25 PCA scattergrams of ranked PIXE data for all Umm al-Nar Period objects 4.26 PCA scattergrams of Urnm al-Nar Period copper objects only 4.27 PCA scattergrams of Urnm al-Nar Period tinbronzes only 4.28 Alloy use in the four Urnm al-Nar Period tomb assemblages Iron and sulfur levels in finished objects in comparison to secondary refining waste from the settlements of Saar and Muweilah Nickel, arsenic, and tin concentrations in Umm al-Nar Period objects Tin concentrations in Urnm al-Nar Period objects analyzed by PIXE, and previously analyzed Iron Age objects from southeastern Arabia Alloy use in different object categories Lead isotope data for massive sulfide deposits from Oman, in comparison to mid-ocean ridge basalts (MORB) Isotopic variability of copper ores from individual ore deposits in Oman LIA data for copper ores from Oman Isotopic composition of Omani ores, in comparison to copper ingots and finished objects from southeastern Arabia and Bahrain

3.1 1 Spearhead TA21 83 from the Tell Abraq Urnm al-Nar Period tomb 3.12 Daggerlknife blade TA2268 from the Tell Abraq Urnm al-Nar Period tomb 3.13 Daggerlknife blade TA2270 from the Tell Abraq Urnm al-Nar Period tomb 3.14 Daggerlknife blade TA2315 from the Tell Abraq Urnm al-Nar Period tomb 3.15 Daggerlknife blade TA2440 from the Tell Abraq Urnm al-Nar Period tomb 3.16 Socketed spearhead TA2757 from the Tell Abraq Urnm al-Nar Period tomb 4.1 Sulfur concentrations in A1 Sufouh, Unarl, Unar2 and Tell Abraq objects 4.2 Sulfur concentrations in all Urnm al-Nar Period objects analyzed by PIXE 4.3 Iron concentrations in AI Sufouh, Unarl, Unar2 and Tell Abraq objects 4.4 Iron concentrations in all Urnm al-Nar Period objects analyzed by PIXE 4.5 Cobalt concentrations in AI Sufouh, Unarl, Unar2 and Tell Abraq objects 4.6 Cobalt concentrations in all Urnm al-Nar Period objects analyzed by PIXE 4.7 Nickel concentrations in A1 Sufouh, Unarl, Unar2 and Tell Abraq objects 4.8 Nickel concentrations in all Urnm al-Nar Period objects analyzed by PIXE 4.9 Arsenic concentrations in A1 Sufouh, Unarl, Unar2 and Tell Abraq objects 4.10 Arsenic concentrations in all Urnm al-Nar Period objects analyzed by PIXE 4.1 1 Selenium concentrations in A1 Sufouh, Unarl , Unar2 and Tell Abraq objects 4.12 Selenium concentrations in all Urnm al-Nar Period objects analyzed by PIXE 4.13 Silver concentrations in all Urnm al-Nar Period objects analyzed by PIXE 4.14 Lead concentrations in A1 Sufouh, Unarl, Unar2 and Tell Abraq objects 4.15 Lead concentrations in all Urnm al-Nar Period objects analyzed by PIXE 4.16 Tin concentrations in A1 Sufouh, Unarl, Unar2 and Tell Abraq objects

xiv

95 98 98 98 99 99

100 100 101 102 102 104

107 120

121 126

135 136 137

137

LIA data for all Urnm al-Nar Period objects from the U.A.E. analyzed in this study LIA data for all Urnm al-Nar Period objects, arranged by site LIA data for all Urnm al-Nar Period objects by alloy category 207Pb1206Pb isotopic composition of Urnm al-Nar Period copper objects from the UAE analyzed in this study 207Pb/206Pb Isotopic ranges for Urnm al-Nar Period objects analyzed in this study LIA data for Urnm al-Nar Period objects analyzed in this study, and Gulf copper ingots analyzed previously LIA data for Urnm al-Nar Period copper objects analyzed in this study, and copper-base artifacts and prills analyzed by Prange et al. (1999: Figure 7) 154 LIA data for Urnm al-Nar Period copper-low tin and tin-bronze objects analyzed in this study, and copper-base artifacts and prills analyzed by Prange et al. (1999: Figure 7) 154 LIA data for Urnm al-Nar Period objects analyzed in this study, and copper-base artifacts and prills from Saar, Bahrain 155 LIA data for Urnm al-Nar Period copper objects analyzed in this study, and copper artifacts and prills from Wadi SuqILate Bronze Age contexts at Tell Abraq (Weeks 1999) 155 LIA data for Urnm al-Nar Period tin-bearing objects analyzed in this study, and tin-bronze artifacts and prills from Wadi SuqILate Bronze Age contexts at Tell Abraq (Weeks 1999) LIA data for copper objects from the U.A.E. analyzed in this study, and Omani copper ores 7.13 LIA data for copper-low tin objects from the U.A.E. analyzed in this study, and Omani copper ores 7.14 LIA data for tin-bronze objects from the U.A.E. analyzed in this study, and Omani copper ores 7.15 LIA data for AsINi-copper objects from the U.A.E. analyzed in this study, and Omani copper ores

7.16 LIA data for Urnm al-Nar Period objects analyzed in this study, and Indian ores and slags 7.17 LIA data for Urnm al-Nar Period objects analyzed in this study, Iranian copper ores and slags 7.1 8 LIA data for Urnm al-Nar Period objects analyzed in this study, and Saudi Arabian copper and tin ores 7.19 LIA data for Urnm al-Nar Period objects analyzed in this study, in comparison to the isotopic characteristics of copper ores from Anatolia, the Aegean, Feinan and Timna 7.20 LIA data for tin (and zinc)-bearing objects from the Aegean and northwestern Anatolia, in comparison to tin-bronzes and copper-low tin objects from the U.A.E. Map showing ore deposits and archaeological and metallurgical sites mentioned in Chapter Eight SR2 target chamber schematic The relationship between PIXE sensitivity and atomic number The relationship between PIXE precision and element concentration 205 Chromium concentrations in al.l analyzed PIXE samples 206

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List of Tables

Chronological periodization of southeastern Arabian prehistory Geology and stratigraphy of the northern Oman Mountains Objects from A1 Sufouh analyzed by PIXE Objects from Unarl analyzed by PIXE Objects from Unar2 analyzed by PIXE AMS Radiocarbon dates associated with the Tell Abraq tomb Objects from the Tell Abraq tomb analyzed by PIXE PIXE compositional data for objects from A1 Sufouh PIXEcompositional data of objects fromUnar 1 PIXE compositional data for objects from Unar2 PIXE compositional data for objects from Tell Abraq Sulfur concentrations in Urnm al-Nar Period objects analyzed by PIXE Sulfur levels recorded in previous analytical studies Iron concentrations in Urnm al-Nar Period objects analyzed by PIXE Ironlevelsrecordedin previous analytical studies Cobalt concentrations in Urnm al-Nar Period objects analyzed by PIXE Cobalt levels in previously analyzed objects Nickel concentrations in Urnm al-Nar Period objects analyzed by PIXE Nickel levels recorded in previous analytical studies Zinc concentrations in Urnm al-Nar Period objects analyzed by PIXE Zinc levelsrecorded in previous analytical studies Arsenic concentrations in Urnm al-Nar Period objects analyzed by PIXE Arsenic levels recorded in previous analytical studies Selenium concentrations in Urnm al-Nar Period objects analyzed by PIXE 88 Silver concentrations in Urnm al-Nar Period objects analyzed by PIXE 90 Silver levels recorded in previous analytical 90 studies

xvii

4.20 Antimony levels recorded in previous analytical studies 92 4.21 Lead concentrations in Umm al-Nar Period objects analyzed by PIXE 92 4.22 Lead levels recorded in previous analytical studies 94 4.23 Tin concentrations in Umm al-Nar Period objects analyzed by PIXE 94 4.24 Rank-correlation coefficients for all Umm al-Nar Period objects 97 7.1 Lead isotope data for objects from A1 Sufouh, Unarl, Unar2, and Tell Abraq 146

xviii

Introduction

Outline and Genesis of the Project This volume presents a study of early metal production, exchange and use in the Persian Gulf region. The issues addressed range from technological aspects of early metal extraction and alloy production, to the broader socioeconomic issues related to the production and trade of metallic resources in the Gulf and the use of tin and tin-bronze in early western Asia (Figure 1). Metallurgical studies have been of primary interest in the archaeology of the Gulf from the earliest periods of work in the region. This is chiefly a result of scholarly debate regarding the location of the lands of Dilmun and Magan, which are mentioned in Bronze Age historical texts from Greater Mesopotamia and which were intimately linked with the supply of copper to the Sumerians, Akkadians and Babylonians in the third and early-second millennia BCE (e.g. Oppenheim 1954; Leemans 1960; Muhly 1973a; Weisgerber 1983; Potts 1B o a : 133-149). Archaeological and Assyriological research in the twentieth century have paid great attention to locating the lands of Dilmun and Magan, and it is now clear that both are to be placed within the Gulf region: Dilmun in the central Gulf, incorporating eastern Saudi Arabia and particularly Bahrain from the later third millennium BCE onwards, and Magan at the southern end of the Gulf, incorporating southeastern Arabia and, perhaps, some areas of southeastern Iran (Heimpel 1987).

While these debates over historical geography date back to the nineteenth Century (Potts 1986:271-272), archaeological research in the Persian Gulf region is a comparatively recent pursuit. Fieldwork in southeastern Arabia was initiated by Danish archaeologists in the 1 9 . 5 0 ~and ~ a great deal of research since that time has allowed the development of a secure chronology for prehistoric southeastern Arabia (Table p), and a somewhat less assured understanding of the economic, technological, social and political characteristics of these early Gulf societies. The archaeological evidence indicates that, by the early third millennium BCE (the Hafit Period), relatively small, sedentary communities existed in southeastern Arabia that were founded upon agricultural subsistence and the exploitation of marine resources (Potts 199713). The evidence for small numbers of copper-base objects from collective Hafit graves (e.g. Frifelt 1975b) suggests that local copper extraction had already begun by this period. This subsistence basis for human settlement persisted into the later third millennium (the Umm al-Nar Period), when it was supplemented by a new form of subsistence adaptation based upon specialized production and exchange of various commodities (e.g. copper, ceramics, and stone vessels) within southeastern Arabia (Cleuziou and Tosi 1989, 2000). This regional exchange network represented a critical adaptation in an environment where resources were plentiful but often strongly localized geographically. The development of an integrated local economic system in southeastern Arabia was contemporary with a dramatic increase in the number of known settlements, and with material remains from settlement and funerary contexts indicating extremely far-flung trade contacts with regions such as Mesopotamia, Iran, the Indus Valley, central Asia and the central Gulf (Potts 1990a, 1993e, 2003a, 2003b). However, settlements remained relatively small, usually no larger than a few hectares, and there is no evidence for the development of large political institutions or significant social hierarchies (Crawford l998:l3 8). In the early second millennium BCE (the Wadi Suq Period) there was a dramatic reduction in the number of settlements, an occurrence that has been related to the increasing importance of nomadic pastoralism as a subsistence regime (Cleuziou 1981; Carter 1997).

Figure 1.1 Major archaeological sites of the U.A.E. referred to in the text.Objects analyzed in this volume come from AI Sufouh, Unarl, Unar2, and Tell Abraq.

2

Early Metallurgy of the Persian Gulf

It is against this background that the evidence for third millennium copper extraction in southeastern Arabia, the "copper mountain of Magan", must be considered. The large scale of this production was demonstrated from the late 1970s through archaeometallurgical research by the German Mining Museum in the Sultanate of Oman (Weisgerber 1980b, 1981; Hauptmann 1985, 1987; Yule and Weisgerber 1996; Weisgerber and Yule 1999; Prange et al. 1999). This ongoing field project established the production of copper in southeastern Arabia from as early as the Umm al-Nar Period, and the high-volume copper trade between the Gulf area and Mesopotamia supported by these studies and by cuneiform references is regarded as crucial in the socioeconomic development of the region in the Bronze Age and later (e.g. Edens 1992). The compositional and lead isotope analyses (LIA) which form the substantive core of this volume were undertaken on copper-base objects of this period, from four Umm al-Nar Period collective assemblages that can be dated between 2450-1900 BCE (see Chapter Three for details). As outlined above, the data and discussions presented in the following chapters exist within a local technological framework largely constructed by the German research in Oman. Nevertheless, the new analyses represent an important complement to the German research in two respects. Firstly, the analyses provide evidence of metal use in settlements that are not associated with primary copper production, which has until recently been the main focus of the German research (although see Prange et al. 1999). Secondly, the analyses are important for our understanding of metal use in more northerly areas of the Oman Peninsula rather than those where the German team has traditionally worked. Looking beyond the data from southeastern Arabia itself, the results of this study can be related to broader regional developments in western Asia, particularly the development of mining, metallurgy and pyrotechnology on the Iranian Plateau, the adoption of new alloys such as tinbronze in neighboring regions of western Asia, and the long-distance trade in metals that linked the Gulf with complex societies stretching from the Indus Valley to Anatolia.

Table 1.1 Chronological Periodization of Southeastern Arabian Prehistory Broad Chronological Phase

Cultural Period

BRONZE AGE

Hafit Period

(3100-1 300 BCE)

Umm al-Nar Period

Absolute Date BCE

Wadi Suq Period Late Bronze Age IRON AGE

Iron I

(1300-300 BCE)

Iron II lron Ill

Chronological periodization of southeastern Arabian prehistory. Note: Periodization after Velde (2003),Potts (1 997b), and Magee (1 996b).

The genesis of the volume lies in previous analyses of material from the site of Tell Abraq in the U.A.E., undertaken by the author in 1995 (Weeks 1997). That study analyzed the changes in copper alloy use at Tell Abraq through the entire occupational sequence of the site: a period of two millennia spanning ca. 2300-300 BCE. The study showed that tin-bronze had been used at Tell Abraq from the earliest phases of its occupation in the third millennium, alongside objects of relatively pure copper and arsenical copper. As such, the findings contrasted strongly with previous studies of early metal use in southeastern Arabia (e.g. Hauptmann 1987; Hauptmann et al. 1988; Berthoud et al. 1980, 1982). These studies had indicated that tin-bronze was extremely rare in the region in the third millennium and was not consistently used until the end of the second millennium. The analyses of the Tell Abraq objects thus raised the question of whether Tell Abraq, clearly the largest site on the Gulf coast of southeastern Arabia during the late-third and second millennia (Potts 1993a), was somehow unique in terms of its access to metallic resources. For example, it has been proposed that Tell Abraq functioned as the chief outlet for Omani copper in the last centuries of the third millennium (Frifelt 1995) and the site may therefore have had greater access to a variety of metal resources and other luxury goods than most sites in the Oman Peninsula. Alternatively, Carter (2001:196) has suggested that Tell Abraq might be best regarded as a trading post between the centrallnorthern Gulf and South Asia; an "exceptional" site not well integrated economically with southeastern Arabia beyond the northern coastal region.

Introduction

3

These early archaeometallurgical analyses from Tell Abraq suggested the possibility of differences in metal procurement patterns between northern and southern areas of the Oman Peninsula. Further basic questions posed by the Tell Abraq analyses related to the chronology of the earliest tin and tinbronze use in the region, and the mechanisms and routes by which this clearly foreign material reached the Gulf. However, due to the dearth of analytical programs on chronologically and geographically related metal objects, the Tell Abraq analyses stood somewhat in isolation. As a consequence, it was difficult to assess whether the site was representative of more widespread metallurgical practices in southeastern Arabia, o r whether it was indeed unique in its metalworking technology and access t o foreign resources. The analyses of objects from three other tomb assemblages in the northern U.A.E., from the sites of A1 Sufouh, U n a r l , and Unar2, are thus significant in providing a more secure analytical basis t o support the discussion of the issues raised by the initial Tell Abraq analyses. Additionally, excavation of the second half of the Umm al-Nar Period tomb a t Tell Abraq was completed in 1997-1998, bringing t o light many more copper-base objects from the late third millennium BCE. The analysis of a sub-set of these newly recovered objects using a fully quantitative technique was deemed desirable, in order to support the results of the semi-quantitative EDS analyses of material from the site undertaken previously. As a group, analyses of the four tomb assemblages allow for a relatively clear understanding of developments in alloying technology and raw material exchange patterns over the last half of the third millennium BCE in the northern Oman Peninsula. Such issues are indeed the focus of much of the discussion presented in this volume. However, other issues such as the organization of copper production in Bronze Age southeastern Arabia, and the local and foreign factors that influenced the scale of production, and the role of the Gulf in the third millennium tin trade are also addressed. These theoretical and substantive issues are outlined below in greater detail.

4

Early Metallurgy of the Persian Gulf

Copper Production and the Bronze Age Economy of Southeastern Arabia One of the main theoretical foci of this volume relates not to the interpretation of the analytical data generated by PIXE and LIA, but to an investigation of the organization of copper production in Bronze Age southeastern Arabia, and an examination of the integration of copper production with other local subsistence activities. As noted above, the Umm al-Nar Period witnessed what many archaeologists have characterized as an increasing level of cultural and economic integration. The exchange of copper produced in the mountainous areas of the interior no doubt played a significant role in this integration. In Chapter Two, the possible effects of feedback between greater economic integration and increasingly specialized craft production are examined in detail. The implications of these factors for our understanding of emerging social complexity in Bronze Age southeastern Arabia are also addressed. The importance of local exchange systems in generating demand for copper is emphasized partly to counteract the prominence that has previously been granted to foreign demand for copper from areas such as Mesopotamia, Dilmun, and perhaps the Indus Valley. It is clear that both local and foreign demand played a role in determining total output of copper in the third millennium, and also the ways in which that production was organized. As will be seen in Chapter Two, the archaeological evidence for particular modes of copper production in Bronze Age Oman is very scarce. Nevertheless, there is some evidence for Bronze Age copper extraction sites producing at very different scales, which might tentatively support the notion of distinct modes of production. Whether such differences can be linked to chronology, production for local or foreign markets, or other factors remains uncertain. Prehistoric copper production in Oman, beginning at around 3000 BCE, also witnesses distinct periods of growth and decline, to the point where long periods of complete abandonment of the industry have been hypothesized in the Late Bronze Age and the Late Pre-Islamic Period. This "periodicity" or "cyclicality" of production is another reflection of changes in local and foreign demand for copper, in addition to environmental factors, changing technology, and historically contingent political

and economic events in southeastern Arabia and neighboring regions of western Asia. In Chapter Two, the many factors that may have caused the periodicity of copper production in southeastern Arabia are examined in detail.

Alloying Practices in Bronze Age Southeastern Arabia Considerable information regarding early metalworking practices in southeastern Arabia is generated by the analytical data presented and discussed in Chapters Four and Five. When the compositional analyses are compared with the work of the German Mining Museum, important factors regarding the production and use of certain alloy types, changes in local ore types exploited, and in the technology of extraction can be examined. A brief note on terminology is required here to facilitate the discussion. All objects made of copper and its alloysarereferred to ascopper-baseobjects. In theanalyzed assemblages from Umm al-Nar Period southeastern Arabia, the most common alloy types are pure copper (which contains less than one percent of arsenic, nickel, zinc and lead, and less than two percent tin), tin-bronze (copper with more than two percent tin), arsenical copper (copper with more than one percent arsenic), and nickel copper (copper with more than one percent nickel). The last two alloy types are commonly grouped together under the label As/Ni-copper, which includes all copper samples with more than one percent of arsenic andlor nickel. No a priori assumptions are made regarding the intentional production of these alloys. Justifications for these definitions can be found in Chapters Four and Five. The discussion of the compositional data focuses on the production and use of tin-bronze and As/Ni-copper. Based upon mineralogical studies of ore deposits in southeastern Arabia, it is suggested that the latter alloy is probably a local product. In addition to the investigation of the particular kinds of Omani ore deposits that may have produced such an alloy, discussion focuses upon the various mechanisms by which As/Ni-copper may have been produced and the material properties that may have differentiated it from pure copper and from tin-bronze. Analyses of alloying processes for the production of tinbronze are also addressed, based upon tin concentrations in the objects and also evidence from minor and

trace element concentrations. Chronological aspects of tin-bronze use in the northern Oman Peninsula are also investigated and significant differences in the use of tinbronze and As/Ni copper for specific object categories are visible. The technological, economic, and ideological factors that may have mediated processes of alloy selection in third millennium southeastern Arabia are discussed in detail.

Investigationof the Bronze Age Tin Trade The investigation of early tin and tin-bronze use in the northern Oman Peninsula is important for understanding early metal use and trade both within the Gulf, and in wider western Asia. The tin sources used in Bronze Age western Asia remain unidentified after more than 50 years of investigation (Muhly 1973a; 1985a; 1993a; Stech and Piggot 1986) and related fieldwork, analytical programs and archaeological debates are actively in progress (e.g. Yener and Vandiver 1993a; Moorey l994:297-30 1; Alimov et al. 1998; Yener 2000). The debate is concerned as much with the trade routes and mechanisms by which tin and tin-bronze may have moved in the third millennium as it is with the absolute source of the material. The discovery of early tin-bronze use at Tell Abraq has highlighted the possible role of the Gulf trade in the distribution of this material, an avenue which had been largely under-emphasized due to the dearth of tin-bronzes reported in other compositional studies of material from Bahrain and southeastern Arabia (e.g. McKerrell 1977:167; Hauptmann et al. 1988; Prange et al. 1999). The archaeological objects from the four Umm al-Nar Period tomb assemblages analyzed in this volume add considerably to the body of evidence for early tin-bronze use in the Gulf. Furthermore, the significance of the timing and frequency of early tin-bronze use in the Gulf for general discussions of Bronze Age Gulf archaeology is addressed. In particular, the possible cultural contacts that might account for the use of tin in the central Gulf and in southeastern Arabia are assessed. Any discussions of this nature rely for their validity upon multiple strands of evidence from geology, archaeology and early textual sources (e.g. Muhly 1985a, 1993a; Penhallurick 1986; Stech and Pigott 1986), and these are presented in detail in order to reach a satisfactory conclusion regarding the likely sources of tin used in the Gulf in the Bronze Age.

Introduction

5

The possible significance of the early tin-bronze exchange in the Gulf for wider western Asia is also considered in detail. The results of the LIA of more than 40 objects from the four Umm al-Nar Period tomb assemblages provide crucial evidence for this discussion. The isotopic data provide important information on the extent of the early tin and tin-bronze trade in western Asia and beyond and the possible technological and socioeconomic implications of this trade are discussed in detail.

Analytical Techniques As noted above, the data presented in this volume involve both compositional and lead isotopic analyses. The compositional analyses were undertaken using the technique of Proton-Induced X-ray Emission (PIXE). Details of the application of the PIXE technique to the objects analyzed in this study, as well as information on accuracy, precision and sensitivity of the data, are provided in Chapter Four and Appendix One. PIXE analyses have been successfully used as the basis of a number of archaeometallurgical analysis programs in the Old World (e.g. Fleming and Swann 1985:142). Currently, the use of LIA is much debated within archaeological science and archaeology in general (e.g. Budd et al. 1995a, 1995b, 1996; Muhly 1995a; Pernicka 1995a; Tite 1996; Knapp 2000; Gale 2001). As the issues surrounding the application of LIA to archaeological provenance studies can be complex, a detailed discussion of the development of LIA in archaeology is given in Chapter Six. LIA can provide extremely useful information in the generation and assessment of novel archaeological hypotheses regarding provenance (e.g. Pernicka et al. 1990, 1993), as demonstrated by the results presented and interpreted in Chapter Seven. Useful results are dependent upon a detailed understanding of both geological and anthropogenic factors controlling lead isotope signatures of archaeological objects, and the value of integrating isotopic and compositional data is clear (e.g. Pernicka 1995a; Bridgford 2000; Begemann et al. 2001). Details of the analytical technique for LIA and information on data precision and accuracy can be found in Appendix One.

6

Early Metallurgy of the Persian Gulf

Outline of Chapters Following this introductory chapter, Chapter Two presents the background to the present study, summarizing all previous geological and archaeological work relevant to early metallurgy in the Gulf region. It incorporates an extensive discussion of the factors that affected the scale and periodicity of early metal extraction in southeastern Arabia; an examination of the organization of Umm alNar Period copper production; an assessment of the integration of various specialized production regimes (including metallurgy) in Bronze Age southeastern Arabia, and; a presentation of the evidence for copper-base object fabrication and alloying technologies. Chapter Three reviews the chronological and contextual information on the objects analyzed in this volume. Chapter Four presents and summarizes the compositional data for all analyzed samples on an element-by-element basis. It concludes with a statistical analysis of elemental correlations in the collected data, and of the chemical characteristics of the archaeological metal assemblages from each of the four funerary structures. The implications of the compositiona1 data and statistical analyses are discussed in Chapter Five, with particular focus upon the types of ores that may have been exploited in the Umm al-Nar Period and the production and use of various local and imported copper-base alloys such as As/Ni-copper and tin-bronze. Chapter Six is a summary of theoretical and practical developments in the application of LIA to archaeology, as a background to Chapter Seven, where the results of the LIA of copper-base objects from the four Umm al-Nar Period tomb assemblages are presented. Particular attention is paid to the possible local and foreign metal sources that were used to produce the analyzed copper-base objects. Chapter Eight focuses more specifically on the possible sources of tin used in the Gulf in the Bronze Age and includes a discussion of the trade routes, exchange mechanisms, and socioeconomic importance of the third millennium BCE tin and tin-bronze trade in western Asia. The overall results of the research are summarized in Chapter 9.

2

Geology and Early Exploitation of Copper Deposits in Southeastern Arabia

This chapter addresses the nature of copper deposits in southeastern Arabia and past archaeological studies of ancient copper production in the region. The first section of the chapter begins with a brief description of the geology of southeastern Arabia, and the A1 Hajjar Mountains in particular, including the basic stratigraphic units, their time of formation, and the mechanisms of their emplacement. Subsequently, a detailed description is given of the various copper deposits of southeastern Arabia, their geological setting, mineralogy, and importance for ancient metal production. In the second section of the chapter, archaeological research into ancient copper production in southeastern Arabia is discussed. Early approaches to provenance and the question of the location of Magan are dealt with first, followed by a section on early geological and archaeological surveys in the region and a discussion of the work of the German Mining Museum in Oman. The discussion of early primary copper extraction in southeastern Arabia concludes with an investigation of the apparent periodicity in copper production in the Bronze and Iron Ages, and an examination of the ways in which copper production was organized and integrated into the broader Bronze Age economy of the region. The chapter concludes with a discussion of changes in the technology of copper-base object fabrication over the course of the Bronze Age, examining both the range of items produced and the alloying practices that are evidenced.

Geology of Northern Oman and Masirah All of the copper deposits of southeastern Arabia, with the exception of those on Masirah Island, are to be found within various geological units of the northern Oman or A1 Hajjar Mountains. In the following sections, brief descriptions of the geology of the A1 Hajjar Mountains and Masirah Island are given, as they form an important basis for the understanding of ancient copper mining and production in southeastern Arabia. Geology of the Northern Oman (A1 Hajjar) Mountains The A1 Hajjar Mountains are comprised of a number of different groups of rocks, whose genesis, location and association have been explained in different ways over the course of geological research in the region, dating as far back as the 1900s (Pilgrim 1908). Although comprehensive local geological research did not begin until the 1960s, the geology of Oman and the U.A.E. is relatively well understood for a number of reasons. In particular, the search for new oil and gas reserves was a primary motivator of early geological research in the region, as was the chance to study the world's best exposed and most complete piece of former oceanic mantle and crust, the so-called "Semail Ophiolite" (Glennie 1995:6-9; Batchelor 1992:109). A number of important general studies of the mountains have been published (e.g. Greenwood and Loney 1968; Glennie et al. 1974; Robertson et al. 1990), as well as publications on specific geological units within the mountains, particularly the ophiolite (e.g. Lippard et al. 1986; Boudier and Nicolas 1988). The various geological divisions used to describe and explain the geology of the northern Oman Mountains (see Glennie 1995; Lippard et al. 1986) are given in Table 2.1 in stratigraphic order (oldest at the bottom). The table indicates the basic bipartite division of the rocks of the region into autochthonous and allochthonous sequences. The autochthonous units, include basement granites and shallow marine sediments that were deposited on the Arabian continental shelf or platform, and which remain in the position in which they formed. These units include the "Basement", "Hajar Supergroup" and "Aruma Group" discussed by Glennie (1995:23-32) and Lippard et al. (1986:9-16) and date from the Precambrian to the Late Cretaceous.

Above these autochthonous units sit two series of allochthonous rocks, so-named because they have been moved from their place of formation into their current position by various geological processes. Allochthonous units are noted in Table 2.1. The lower of these units, the "Hawasina," is composed largely of marine sediments that were deposited on the floor of an ancient ocean called the Neo-Tethys, which lay to the northeast of Arabia, between mid-Triassic and mid-Cretaceous times (ca. 270-70 million years ago [Ma]; Lippard et al. 1986:12; Glennie 1995:4). The upper allochthonous unit is the Semail Ophiolite, a section of oceanic upper mantle and crust that formed on the floor of one part of the Neo-Tethys in the Mid-Cretaceous (ca. 105-170 Ma; Glennie 1995:4-5). From about 105 Ma, active spreading ridges in the Neo-Tethys and the South Atlantic Ocean focused great horizontal compressive forces upon the oceanic crust of the Neo-Tethys, causing it to rupture and leading to the formation of an eastward-dipping subduction zone (Glennie 199553). It was in fact the presence of this subduction zone that led to the formation of the Semail oceanic crust in the associated back-arc environment of the subduction zone (Lippard et al. 1986:Figure 4.11). As described by Glennie (1995:5), at 105 Ma these three groups of rocks (the autochthonous series and the two allochthonous series) lay side-by-side, with the granites and shallow marine sediments of the Arabian shelf to the west and the newly-forming oceanic crust of the Semail to the east. The Hawasina sediments overlay older and deeper oceanic crust in between the Arabian platform and the Semail crust. The subduction zone in the Neo-Tethys and the compressive forces which initiated the formation of the Semail oceanic ridge led to the emplacement of first the Hawasina sediments and then the Semail oceanic lithosphere over the Arabian shelf in the period between about 105 and 70 Ma. The relative direction of transport was from northeast to southwest, and the distances involved were of the order of several hundred km (Shackleton and Ries 1990:721). Horizontal compressive forces ceased to operate at around 75 Ma, and the uplift of the partially subducted, buoyant continental crust onto which the Hawasina and Semail units had been emplaced led to the detachment of the Semail nappe

8

Early Metallurgy of the Persian Gulf

from its contiguous oceanic crust and the local elevation of parts of the nappe above sea level for the first time (Glennie l995:%-56). At this time, however, the rock units formed a chain of low-relief islands rather than a mountain range. It was not until approximately 30 Ma that these units were uplifted to form the Oman Mountains, as a result of the compressive forces arising from the separation of Arabia from Africa and the collision of the Indian plate with the southern edge of Eurasia (Glennie 199.55). In the intervening period between about 70 and 30 Ma (Mastrichtian-Lower Tertiary), shallow marine sediments were deposited above a number of the rock units that formed the island arc. These units remained in their relative place of formation after the uplift of the Oman mountains, and are thus referred to by Glennie (1995:Table 1)as "neo-autochthonous". The Oman Mountains, in their present form, comprise an arc more than 700 km long and up to 150 km wide, parallel to the Gulf of Oman. They extend from the Musandam Peninsula and the Straits of Hormuz in the north to Ras a1 Hadd in the southeast at an elevation of generally between 500-1,500 m, although Jebel Akhdar rises to ca. 3,000 m (Lippard et al. 1986:l-2). The rock formations that comprise the Oman Mountains are illustrated in Figure 2.1. The most extensive geological unit of the mountains is the Semail Nappe, with an area of approximately 20,000 km2 and a thickness of between five and ten kilometres, which has been broken into 12 generally intact blocks of varying sizes as a result of erosion and of faulting during and after emplacement (Glennie et al. 1974). The Hawasina outcrops mostly on the southern and western extremities of the Oman Mountains, but also occurs in the interior of the mountains, for example at the type site of the "Hawasina Window" in Wadi Hawasina, and in the Dibba Zone in the north. The upper and lower autochthonous units of the mountain range are exposed in the region of Jebel Akhdar, in the mountains south of Muscat, in the Huqf region, and at the northern end of the Oman Mountains in the Musandam Peninsula. Neo-autochthonous rocks are seen in the A1 Ain region, particularly at Jebel Hafit, and in the coastal region between Saih Hatat and Ras al-Hadd in Oman (Glennie 1995:Figure 10).

Table 2.1 Tectonostratigraphic Units of the Northern Oman Mountains

Age (Ma BP)

Formed 105-95

Stratigraphic Unit

Mostly shallow marine limestones (Maastrichtian-EarlyTertiary) of:

1) the Hadhramaut Group, and;

Oceanic crust (Mid-Late Cretaceous), consisting of:

1) a crustal sequence of extrusive basaltic pillow lavas and interbedded pelagic sediments; a sheeted dyke complex; high-level plutonic rocks; and layered peridotites and gabbros; 2) a mantle sequence of peridotites and harzburgites, and; 3) a basal metamorphic sheet of amphibolites and

Formed 270-70

Mostly calcareous sandstones (U. Permian-Turonian) deposited as turbidites, comprised of:

1) the Umar Group; 2) the AI AridhIKawr Groups, and; 3) the SumeiniIHamrat Duru Groups (including the Wahrah Formation).

"Aruma Group" (AllochthonousUnit) 1) Simsima limestones (U.Cretaceous-L.Tertiary); 2) Fiqa shales and conglomerates of the Juweiza Formation (Campanian),and; 3) conglomerates and turbidites of the Muti Formation (Santonian-Campanian). 270-90

"Upper Autochthon" (= Hajar Supergroup) Shallow marine limestones and dolomites comprised of (in the central mountains):

1) the Wasia Group (M. Cretaceous); 2) the Kahmah Group (L. Cretaceous);

3) the Sahtan Group (Jurassic),and; 41 the Akhdar Grow (U. Permian-U.Triassic).

650-270

"Lower Autochthon" A sedimentary sequence of limestones and dolomites consisting of:

1) Palaeozoic siltstones of Saih Hatat, Quartzites of J. Qamar and J. Ramaq, and;

2) Eocambrian rocks of the eastern Huqf. 850-650

"Basement" (AutochthonousUnit) Jebel Ja'alan sedimentary rocks (Precambrian)

Geology and stratigraphy of the northern Oman Mountains.

Geology and Early Exploitation of Copper

9

Figure 2.1 The geological units comprising the Oman Mountains.

Geology of Masirah Island Masirah Island is located 24 km off the southeastern coast of Oman (Figure 2.2). The island is 64 km long and up to 16 km wide, with a highest elevation of 277 m (Moseley 1969:293-294). It contains a suite of rocks that are very similar to those of the Semail Nappe, including mantle serpentinites, ultramafic to gabbroic cumulates, massive gabbros, sheeted dykes, basaltic pillow lavas and radiolarian cherts (Abbotts 1981; Moseley 1990:665). These rocks were originally thought to represent a part of the Sernail Nappe (Moseley 1969; cf. Moseley and Abbotts 1979), however, recent geological research has determined that the ophiolitic rocks of Masirah are genetically unrelated to the mainland ophiolite, being late Jurassic-Early Cretaceous in age (145-125 Ma; Gnos et al. 1997; Meyer et al. 1996; Smewing et al. 1991).

10

Early Metallurgy of the Persian Gulf

The ophiolitic rocks of Masirah Island are unusual in that they were emplaced a long time after their formation, having drifted in oceanic lithosphere for approximately 90 Ma (Meyer et al. 1996:187). There are actually two distinct ophiolite nappes on Masirah Island (Gnos and Perrin 1996:55), the upper of which was obducted onto the lower between the late Maastrichtian and the pre-Eocene (ca. 60-50 Ma; Gnos and Perrin 1996:62). It is likely that the emplacement of the lower Masirah Ophiolite onto the Arabian shelf was related to the northward movement of the Indian plate (although this is a complicated issue; for a full explanation and illustration, please see e.g., Moseley and Abbotts 1979; Shackleton and Ries 1990; Smewing et al. 1991), and took place slightly after the obduction of the upper ophiolite nappe onto the lower (Gnos and Perrin 1996:62).

Figure 2.2 The major copper deposits and metallurgical sites of southeastern Arabia (triangles) and third millennium settlements (small circles).

Geology and Early Exploitation of Copper

11

Copper Deposits in Southeastern Arabia The vast majority of copper deposits in southeastern Arabia (Figure 2.2) are hosted in rocks of the Semail Ophiolite, the formation and emplacement of which is described above. As shown in Table 2.1, the Semail Ophiolite consists of rock series with both mantle and crustal origins. The mantle series is the lowest stratigraphic unit in the Semail Nappe, and is composed mostly of variably serpentinized ultramafic rocks (mostly tectonized harzburgites and dunites) with an estimated maximum thickness of 10-12 km (Lippard et al. 1986:41). The peridotites of the mantle series are overlain by a magmatic assemblage of cumulate gabbros and peridotites up to four km thick (the "Layered Series"), and a sequence of high-level plutonic rocks (the "HighLevel Intrusives"), generally gabbros, of up to 500 m thick (Lippard et al. 1986:14, 41). The high-level intrusives are stratigraphically overlain by a sheeted diabase dyke complex of up to 1.5 km in thickness, which acted as a feeder for an overlying extrusive sequence of basaltic pillow lavas up to two km thick. The extrusive basalts are interbedded and overlain by pelagic sediments (Lippard et al. 1986:41, Figure 3.3). Massive Sulfide Deposits of the Semail Extrusive Series The largest copper deposits in southeastern Arabia are those concentrated in the Semail upper extrusive sequence. These massive sulfide deposits are stratabound within the pillow lavas of the ophiolite, although they are not exclusively associated with any particular stratigraphic interval, and are directly comparable to the large copper deposits of the Troodos Ophiolite in Cyprus (Coleman 1977:124-126; Batchelor 1992:108; Lippard et al. 1986:127). The copper, iron and zinc-rich ores are exhalative sedimentary deposits formed either in sea-floor depressions near oceanic ridges or as a result of sea-mount volcanism (Ixer et al. 1984:123; Hauptmann 1985:27). The ore metals themselves originated in the volcanic rocks, from which they were mobilized by hydrothermal seawater solutions (Jankovic, 1986:27; Hauptmann 1985:27). The massive sulfide deposits are comprised primarily of pyrite (FeS2),chalcopyrite (CuFeS2),and sphalerite (ZnS), but exhibit well-developed gossans consisting of brightly colored iron oxides, hydroxides and sulfates in

12

Early Metallurgy of the Persian Gulf

addition to secondary copper minerals such as malachite ( C U ~ C O , ( O H ) azurite ~), ( C U ~ ( C O ~ ) ~ ( and O H rare )~) native copper (Coleman 1977:125; Ixer et al. 1984; Hauptmann 1985:26; Weisgerber 1987: 170). Cementation zones or zones of secondary enrichment are not seen in the massive sulfide deposits (Hauptmann 1985:25; Hauptmann et al. 1988:35), although there are considerable quantities of secondary sulfur-containing minerals such as bornite (Cu5FeS4),chalcocite (Cu2S) and covellite (CuS) in some deposits (Ixer et al. 1984:120 and Table 2; Smewing et al. 1977536). The three largest deposits in the region occur in the hinterland of Sohar, at the sites of Bayda, Lasail and 'Arja, while other massive sulfide deposits and stockworks are known at Zuha, Raki, Hayl as-Safil and Daris in the Sultanate of Oman (Calvez and Lescuyer 1991). Detailed summaries of the formation and mineralogy of these deposits can be found in numerous publications (e.g. Ixer et al. 1984, 1986; Hauptmann 1985:25-27; Lippard et al. 1986:127-128; Lescuyer et al. 1988; Calvez and Lescuyer 1991; Batchelor 1992; A1 Azry et al. 1993). The extrusive lavas of the upper Semail ophiolite were formed as a result of two separate but nearly contemporary magmatic events (M1 and M2). The formation of the first series of pillow lavas (the V1 or Geotimes unit), which forms the footwall of all the main massive sulfide deposits in southeastern Arabia, was related to the first magmatic event. The Geotimes Unit directly overlies the sheeted dyke complex from which it was derived (Batchelor 1992:114) and was formed in late Albian to early Cenomanian times (Calvez and Lescuyer 1991). The Bayda massive sulfide deposit is thought to have been formed by hydrothermal activity at this time (Batchelor 1992: 114). The upper lava unit (V2, consisting of the Lasail and Alley Units) is related to the second magmatic event (M2), and its earliest manifestations are associated with the hydrothermal activity that formed the massive sulfide deposits at Lasail and 'Arja, as well as those at Zuha, Raki and Hayl as-Safil (Batchelor 1992:114). Thus, the majority of massive sulfide deposits in the Semail Ophiolite occur at the contact between the V1 and V2 volcanic units. The Lasail ore deposit has a hanging-wall of Lasail Unit lavas, whereas the 'Arja deposit has a

hanging-wall of Alley Unit lavas (Ixer et al. 1984:Figure 2). This volcanic and hydrothermal activity is of Cenomanian to Turonian age and represents the most important period of copper mineralization related to the Oman Mountains (Batchelor 1992: 114). Other Copper Deposits of the Semail Ophiolite Although the largest copper deposits of the Oman Mountains occur as massive sulfide deposits in the upper extrusive sequence, smaller vein-type deposits are in fact found throughout the ophiolite crustal sequence and in mantle sequence rocks (Hauptmann 1985:21-3 1).Minor sulfide concentrations are found in the sheeted dyke complex (Weisgerber 1 9 8 0 ~115; : Weisgerber l98Oa: 89; Hauptmann and Weisgerber 1980:134) and high level gab bros, often associated with northwest-southeast trending faults (Coleman 1977:124; Lippard et al. 1986:128). Copper deposits are also known from lower in the crustal sequence, at the contact between cumulate gabbro and cumulate peridotite near the petrological Moho (Coleman et al. 1978:12; Weisgerber 1980c:115; Weisgerber 1981:190), and along major fractures within the mantle harzburgites (Goettler et al. 1976:46-47; Hauptmann 1985:21-31; Lorand 1988; Batchelor l992:ll4). It is likely that a lot of this fracture mineralization is related to mineralization at higher levels within the ophiolite extrusive sequence (Batchelor 1992:114), although some deposits lie along northwest-trending faults related to younger tectonics (Coleman et al. 1978 12). Although these deposits are generally small, with lengths of less than 600 m and widths of less than 20 m (Hauptmann 1985:27; Batchelor l992:l l 4 ) , they are frequently of high grade and contain significant quantities of secondary minerals such as brochantite ( C U & ~ ~ ( O Hmalachite, )~), azurite and chrysocolla (CuSi03.2H20)in addition to primary chalcopyrite and pyrite (Goettler et al. 1976:47-50; Hauptmann 1985:26; Hauptmann et al. l 9 8 8:35). Geological researchers in southeastern Arabia have commonly noted an association between ancient slag heaps and these lower ophiolitic copper deposits (Greenwood and Loney l968:3 1; Glennie et al. 1974:284; Goettler et al. 1976; Coleman et al. 1978; Batchelor 1992:114), and have therefore suggested that these ores, rather than those of the massive

sulfide deposits, were of the greatest importance for early metallurgy in the region (Goettler et al. 1976:47; Hauptmann et al. 1988:35). There are significant differences in the mineralogy of the massive sulfide deposits and those from lower in the ophiolite sequence (Hauptmann 1985:21-31) which, when compared to compositional data from the analysis of archaeological copper-base objects, also support such a conclusion (Hauptmann et al. 1988:35). It should, however, be noted that significant amounts of low-grade oxidized copper minerals were available in the gossans (i.e. the upper weathered zones) of the massive sulfide deposits of the extrusive sequence (Weisgerber 198Oc:115-1 16), and that a number of these deposits in the vicinity of Wadi Jizzi were worked as early as the third millennium BCE (Weisgerber 1987:145). This is in contrast to the evidence suggesting that the unaltered primary copper ores of the massive sulfide deposits (i.e. chalcopyrite and bornite) were not worked on a significant scale until the local Iron Age, around the beginning of the first millennium BCE (Weisgerber 1987:145). Ophiolitic Copper Deposits on Masirah Island A common feature of ophiolites is the occurrence of massive sulfide deposits in the various rock units, particularly extrusive rocks, of which they are comprised (Coleman 1977:124). There are thus strong a priori reasons to suspect the presence of copper deposits on Masirah Island. In fact, copper mineralization was reported on Masirah Island as early as the 1840s (Carter 1848) in the form of disseminated carbonates (malachite and azurite) associated with haematite (Fe203)in quartz veins (Batchelor 1992:117). Other copper mineralizations are found in rocks of the sheeted dyke complex (Moseley 1990:Figure 5 ) and pillow lavas on the island (Moseley and Abbotts 1979:Figure l ) , and it has been suggested that the Masirah Ophiolite and small ophiolites at Ra's al-Madrakah and Ra's al-Jibsch on the nearby mainland "carry obvious potential for Cyprus-type copper mineralization" (Batchelor 1992:117). Only a small amount of archaeological work has been carried out on Masirah Island, but even the earliest geological reports mention the presence of ancient slag heaps (Batchelor 1992:117). Archaeological information

Geology and Early Exploitation of Copper

13

and radiocarbon analyses indicate that copper mining on Masirah Island can be placed at least as early as the eighteenth century BCE (Weisgerber l 9 8 8:footnote 7; Weisgerber 1991:327), and the copper of the island is therefore significant for discussions of Bronze Age production and trade in the region. Non-Ophiolitic Copper Deposits in Southeastern Arabia In addition to copper deposits within rock units of the Semail Ophiolite, small copper mineralizations can be found within stratigraphic units that underlie the Semail Nappe. Both massive sulfide and vein-type mineralization is found within Hawasina rocks in the Sultanate of Oman and the U.A.E. (e.g. Hauptmann et al. 1988:48). The largest Hawasina hosted copper deposit is that at A1 Ajal, not far from Muscat (Lescuyer et al. 1988; Calvez and Lescuyer 1991). This Late Permian (>250 Ma) deposit, roughly 100 m long and five m thick, has high levels of gold and silver but a relatively low concentration of copper in the gossan as a result of considerable leaching (Batchelor 1992:117). Further to the north, a number of geological surveys in the U.A.E. (Greenwood and Loney 1968; Hassan and Al-Sulaimi 1979) have demonstrated small veins of fracture-related copper mineralization in Hawasina rocks. The mineralization is usually of chalcopyrite with varying quantities of secondary copper carbonates (malachite), silicates (chrysocolla) and secondary sulfur-bearing species such as chalcocite (Greenwood and Loney 1968:29-3 1, 51). At present, there is no archaeological evidence for the exploitation of Hawasina-hosted deposits in southeastern Arabia.

Early Research into Ancient Copper Production in the Oman Peninsula Cuneiform Sources Referring to Dilmun, Magan and Meluhha The investigation of copper production in the region of southeastern Arabia began with the study of Mesopotamian Bronze Age cuneiform documents. Over the course of the third and early second millennia BCE the Gulf, known to the Mesopotamians as the Lower Sea, was the most critical trade route for the supply of luxury goods and some essential raw materials to the Mesopotamian alluvium (T. F. Potts 1994). A significant

14

Early Metallurgy of the Persian Gulf

body of cuneiform texts, dating from the Jemdet Nasr Period to the Old Babylonian Period, records the exchange of cloth, textiles, grain, silver, oils and other Mesopotamian manufactured goods with polities of the Lower Sea, for the procurement of various types of wood, semi-precious stones, ivory and above all, copper (Leemans 1960:lO-12; Oppenheim 1954). These cuneiform texts are our earliest historical references to copper trade in the Gulf region, and are reviewed here due to their importance for reconstructions of early copper production in southeastern Arabia. The three toponyms associated with the Gulf trade are Dilmun, Magan and Meluhha, each of which is mentioned as a supplier of copper at various periods in Mesopotamian history: Magan and Meluhha are referred to only in the Sargonic-Ur I11 periods (ca. 2350-2000 BCE), whereas the toponym Dilmun occurs from the Late UrukIJemdet Nasr Period through to the Isin-Larsa and Old Babylonian Periods, ca. 3100-1750 BCE (Heimpel 1987, 1988, 1993; Potts 1990a). There is a strong agreement between archaeological and textual evidence for locating Dilmun on the Arabian littoral of the central Gulf, incorporating Tarut Island by the middle of the third millennium BCE and concentrated primarily on the islands of Bahrain and Failaka by the beginning of the second millennium BCE (Crawford l998 :1-8 and Figure 1.2; Potts 1990a). Likewise, the archaeological evidence for extensive Bronze Age copper extraction in the Sultanate of Oman (see below) can be correlated with cuneiform references to Magan as a major supplier of copper, in order to suggest that Magan encompassed the area covered by the modern countries of the U.A.E. and Oman (Potts 1990a:133-149; Heimpel 1988). An association between the Oman Peninsula and the Sumerian copper-supplying land of Magan had already been suggested in the nineteenth century based upon geographical considerations (Potts 1986:271-272), and by the second decade of the twentieth century early historical references to copper production in Oman had been used to support the association (Potts 1990a:117). However, the details of a number of Old Akkadian military campaigns against the region (and the booty they brought back to Mesopotamia) are more equivocal, and suggest the possibility that areas on the north of the Straits of Hormuz were also included within the

Mesopotamian conception of Magan (Glassner 1989; Heimpel 1987). Although the possibility of a political entity spanning the Straits of Hormuz finds parallels in more recent Sasanian-early Islamic polities which did just that (Wilkinson 1979:889), archaeological assemblages from each side of the Gulf are so distinct as to suggest that Magan occupied only southeastern Arabia. Almost all the third millennium BCE cuneiform texts from southern Mesopotamia which mention specific toponyms as copper sources speak of copper from either Magan or Dilmun (T. F. Potts 1994:Table 4.1). Meluhha, the third polity of the Lower Sea, is mentioned only rarely as a copper supplier, and then for amounts of only a few kilograms (Leemans 1960:161). The common association of Meluhha with the supply of carnelian, lapis lazuli, gold, precious woods, and especially ivory, suggests that the toponym is to be related to the region between the Makran coast and Gujarat, encompassing sites of the Indus civilization (Heimpel 1993).

Dilmun and the Pre-Sargonic Gulf Trade Cuneiform references to Dilmun occur as early as the late fourth millennium BCE, in both lexical lists and economic documents of the "Archaic Texts" from the Eanna precinct in Uruk. In these texts, Dilmun is mentioned in association with a particular type of metal axe, and there is a partial text which refers to Dilmun copper and another which mentions a Dilmun garment (Nissen 1986; Englund 1983). From Pre-Sargonic Lagash, texts from the reigns of Lugalanda and Urukagina in the twenty-fourth century BCE indicate the receipt of Dilmun copper from the merchant Ur-Enki, in quantities on the order of 100 kg. Contemporary texts show that items such as milk, cereal products, fat, salve and possibly cedar resin, in addition to the wool and silver more commonly seen in later periods, were traded to Dilmun in return for copper and wood. Such successful trading expeditions seem to have been commemorated by the dedication of bronze models of Dilmun ships to the goddess Nanshe, at her temple in Lagash (Potts 1990a:182). There are also a number of references to Dilmun in the cuneiform documents from Ebla in Syria, dated to the mid-third millennium. Dilmun occurs as a toponym and as an element in professional titles (Potts 1986:Table l),

and it seems that the Dilmun shekel was used in economic transactions in Ebla (Potts 1986:Table 1; Pettinato 1983). Significantly, there are also references to Dilmun copper and Dilmun tin at Ebla (Pettinato 1983:77-78). As there are no known copper sources in eastern Saudi Arabia or Bahrain, these early references to Dilmun copper are usually taken to indicate Dilmun's role as a transhipment center for copper produced further afield. The later significance of Magan as a copper supplier, and the evidence of copper production in the later third millennium in southeastern Arabia, are often invoked as reasons to see the earliest Dilmun copper as originating in the Oman Peninsula (e.g. Cleuziou and Mkry 2002:282). As has been described above, there is evidence for the widespread use of copper-base objects in southeastern Arabia by the late fourth millennium BCE, but as yet local production has not been conclusively demonstrated before the Umm al-Nar Period (see below). Thus, the hypothesis that the early-third millennium cuneiform references to Dilmun copper reflect primary copper extraction in southeastern Arabia is yet to be verified.

Gulf Trade in the Old-Akkadian t o Ur 111 Periods By the Old Akkadian Period, direct connections are established between all the polities involved in the Gulf trade. This fact is most clearly indicated by the claim of Sargon that, under his rule, ships from Dilmun, Magan and Meluhha docked at the quay of his city at Agade (Heimpel 1987:no. 13). Economic texts detailing commercial traffic with Dilmun are relatively scarce at this time (Potts 1990a:183), although Dilmunites and Dilmun boats are still mentioned. A particular type of copper traded at the time, designated as urudu-a-EN-da, is known from a handful of Old Akkadian texts, and is thought to represent copper from Dilmun. In a number of texts this type of copper is explicitly recorded as having come from Dilmun, and Waetzoldt and Bachmann (1984:6) regard urudu-a-EN-da as coming from Dilmun even when the source is not specifically identified. Dilmun's role in the Gulf trade in wood and copper is further documented by inscriptions of Gudea of Lagash (Potts l99Oa:l84). Copper from Magan itself is mentioned in only very minor quantities at this time (Heimpel 1987:no. 20), and Manishtusu's reference to a

Geology and Early Exploitation of Copper

15

campaign against a region across the Lower Sea, where he traveled to the metal mines, is rather equivocal: although the crossing of the Lower Sea from Sherihum (in Iran) would suggest a location somewhere on the Arabian side of the Gulf, Magan is not mentioned by name, and the mines are said to be for KU, usually translated as "silver" or "precious metal" (Glassner 1989). Thus, it is difficult to regard the text as the first historical reference to copper production in Oman (contra Potts 1990a:138), although Glassner's (l989:186) claim that the lack of silver in southeastern Arabia suggests that Magan lay on the Iranian side of the Gulf is contradicted by medieval references to silver and gold mines in Oman (Weisgerber l987:147). By the Ur I11 Period, Magan seems to have been more important than Dilmun in the Gulf trade, and merchants from Ur traded directly with Magan. There are no references to copper traded from Dilmun at this time, even though there are scattered references to Dilmunites in Southern Mesopotamia and to a continued trade with Dilmun (Potts 1990a:186). A number of texts from the reign of Ibbi-Sin indicate that a Mesopotamian merchant by the name of Lu-Enlilla received large amounts of garments and wool (and at other times, oil and leather objects) from the storehouse of the temple of Nanna in order to buy copper in Magan (Leemans 1960:19). These economic documents are supplemented by a slightly earlier text which indicates that the temple received from LuEnlilla a tithe of goods that were obtained on a trip to Magan: not only copper (more than 150 kg), but also beads of semi-precious stones, ivory and "Magan" onions (Oppenheim 1954:13; Leemans 1960:21). Dilmun in Isin-Larsa and Old Babylonian Sources Magan is not mentioned in cuneiform sources after the Ur I11 period, and there is a corresponding increase in the frequency of references to Dilmun, which is particularly associated with the acquisition of copper (Oppenheim 1954:15). From the Larsa Period at Ur, specifically the tenth-nineteenth years of the reign of Rim-Sin (ca. 1813-1 804 BC on the Middle chronology: Van de Mieroop 1992:136-137) there exist a number of famous texts related to the activities of Ea-nasir, an alik Tilmun or Dilmun trader, who was involved in the copper trade in the Gulf. Individual maritime trading expeditions to

16

Early Metallurgy of the Persian Gulf

Dilmun, probably undertaken by Ea-nasir himself (Leemans 1960:52), were financed by large numbers of investors, who each contributed a small amount of capital to the mission in the form of silver rings, baskets, sesame oil, and textiles (Van de Mieroop 1992:196). Upon return from Dilmun, the proceeds were divided amongst the investors, who frequently complained about the quality of the copper that had been supplied to them (Oppenheim 1954:lO-11). Although the archives from the house of Ea-nasir indicate that the trade was undertaken by private merchants, the Palace was involved in proceedings as sometime investor, and through the collection of taxes upon the completion of the expedition (Van de Mieroop 1992:197; Leemans 1960:SO). Leemans (1960:54), in fact, sees the Palace as Ea-nasir's major client. Earlier in the second millennium, it seems that the Ningal temple was more involved in the trade than the Palace, insofar as tithes of goods or votive offerings procured by Dilmun traders were deposited at the temple (Leemans 1960:19-22; Van de Mieroop 1992:197). The volume of the copper trade was large: texts from the early Larsa period contain references to tithes of hundreds of kilograms of copper from trade expeditions to Dilmun (Leemans 1960:23-36), while individual texts from the from the house of Ea-nasir in Ur mention up to 18,000 kilograms of copper (Leemans 196050). Oppenheim (1954: 13) contrasts the copper trade undertaken by Ea-nasir with that of Lu-Enlilla from the Ur I11 Period. The goods traded between Mesopotamia and the Gulf in the Lu-Enlilla and Ea-nasir archives are very similar, but the economic context of financing the venture is different: in the Larsa Period, Ea-nasir acted a private merchant (even though the Palace may have closely monitored and been a major beneficiary of the trade), whereas in the Ur I11 Period, Lu-Enlilla seems to have been an agent of an institution, the Nanna temple (Oppenheim 1954:14). Sometime between the fall of Larsa and the decline of the Dynasty of Hammurabi, Dilmun ceased to supply copper to southern Mesopotamia. Although still mentioned in cuneiform sources, it was known only for its local agricultural products and sweet water, not as a supplier of copper (Oppenheim 1954:15-1 6). Crawford (1996, 1998:154-155) has suggested that this was probably the result of the disruption caused by the establishment of a

unified Babylon under Hammurabi, and his conquest of Mari and the middle-Euphrates region. Hammurabi's actions simultaneously decimated Mesopotamia's major point of access to the Gulf trade, led to a widespread depopulation of southern Mesopotamia, and opened up routes to alternative copper sources in Anatolia and the Mediterranean. It is perhaps no coincidence that a text from the fifth year of the reign of Hammurabi's successor, Samsu-Iluna, bearing the first cuneiform reference to copper from Cyprus (Alashiya), also contains the last reference to Dilmun copper (Potts 1990a:226; Crawford 1998:155). As for the earlier periods of the Gulf trade, the copper of the Dilmun trade in the Isin-Larsa and Old Babylonian Periods is most commonly regarded as having originated in southeastern Arabia. As outlined below, however, the evidence for copper production at this period in the Oman Peninsula is extremely limited, a situation which is surprising given the fact that the Gulf copper trade seems to have reached its greatest extent at this time. Any hypotheses suggesting the exclusive origin of early second millennium Dilmun copper in Oman are impossible to evaluate at this stage, and will require extensive archaeometallurgical research to verify.

Arab and European Historical Sources There is an enormous chronological gap before the next historical references to copper production in southeastern Arabia in the tenth century CE. These sources consist of Arab historical and legal documents from the medieval period and later (Weisgerber 1987:l47-148), which are supplemented by the accounts of early European explorers in the Gulf region (Potts l99Oa: 114-1 17). They possess the distinct advantage of referring directly to copper production in Oman, rather than to the trade through the Gulf of copper which may or may not have originated in southeastern Arabia. Amongst the earliest of these sources is the Arab historian and geographer Abul Hasan Ali Al-Mas'udi, who visited Sohar in the early tenth century CE and noted that copper was produced in the region. A later Persian manuscript from the fourteenth century CE by AlMustaufi indicates the production of gold, silver and iron in southeastern Arabia (Weisgerber 1987:147), but does not mention copper. These accounts were substantiated

by those of eighteenth and nineteenth Century European explorers in the region such as Carsten Niebuhr, J. R. Wellsted, H. J. Carter, A. Germain and S. B. Miles (Potts 1990a:114-116; Carter 1848). These observers refer consistently to local copper mines in Oman and on Masirah Island, although the operational status of these mines appears uncertain. There are also Arabic historical texts dealing with mining regulations in Oman. The earliest reference is alJami by Ibn Ja'far which dates to ca. 900 CE, while mines in the vicinity of Izki and in Wadi al-Jizzi are mentioned in the twelfth century CE without specific reference to the materials extracted from them (Weisgerber 1987:147; Potts l99Oa:ll4). The records indicate that mines could be sub-let from their owners, probably merchants in Sohar, for 10 percent of the net profit of the mine (J. C. Wilkinson 1979:892). Rules existed to cover the leasing of mines when the lessee had terminated work or when rent was not being paid. Mining licenses could be unlimited, but could also be granted for limited time periods of up to 100 years, and included details of the topographical limits of the claim (Weisgerber 1987:148). Additionally, partnerships existed between owners and miners, in which profits and risks were shared (Weisgerber 1987:148). These early legal documents and historical sources, in addition to the reports of the first European explorers in the region, provide important information which cannot necessarily be supplied by archaeological evidence alone. For example, information on the administration and legal control of mining in the tenth century CE adds considerably to our understanding of the organization of production at this time, while the limited evidence for local production recounted by later European explorers can also corroborate archaeological evidence of declining production in the second millennium CE. Unfortunately, the accuracy of some of the European material is questionable (Potts 1990a:115), while the Arabic sources focus primarily upon the laws of mine ownership and the division of profits (Potts 1990a:114-115; Weisgerber 1987:147-148), without mentioning important operations such as ore concentration, smelting, and refining. Archaeometallurgical evidence will always be critical in supplying evidence for copper production in periods where historical data are lacking, and for providing a material framework to aid in the interpretation of historical records when they exist.

Geology and Early Exploitation of Copper

17

Early Scientific Analyses The earliest scientific investigation of copper production in the region was undertaken in the 1920s, as one component of research into the sources of copper used by the Sumerians (Peake 1928). In this analytical program, a number of early copper objects from Mesopotamian sites such as Ur, Kish and Tell alUbeid, were analyzed for their composition. It was hoped that such analyses, when linked with analyses of ores and slags from western Asian mining regions, could have provided evidence of which sources were most likely to have provided the copper used by the Sumerians. The conclusions of the study were founded upon the idea that relatively high percentages of nickel characterized both the ore sample from Oman and early copper objects from Mesopotamia. It followed that, during the third millennium, at least some copper used in Mesopotamia was obtained from Oman (Peake 1928). While recent research has indeed indicated that this conclusion is true, the metallurgical bases of the arguments used in the Antiquity article are in fact erroneous. Modern geological and archaeological research indicates that nickel occurs in many copper deposits of western Asia (Cheng and Schwitter 1957:351; Muhly 1973a:229), and therefore high nickel levels in archaeological objects cannot be used to suggest that early Mesopotamian copper came from the relatively nickel-rich deposits of Oman. Additionally, nickel does not occur with the same frequency in all the copper deposits of Oman and the U.A.E., meaning that copper produced in southeastern Arabia could have very low levels of nickel (Hastings et al. 1975:lS; Goettler et al. 1976:46-47; Batchelor 1992). In general, the reliability of using compositional data to source archaeological objects of copper has been increasingly questioned since the 1970s (e.g. Craddock 1976; Craddock and Giumlia-Mair l 9 8 8; Pollard and Herron 1996:302 ff.; Budd et al. 1996; Pernicka 1999). Another problem with this early study was the extremely small database employed to support hypotheses of provenance. A total of only 20 archaeological objects were analyzed, along with one copper slag and one ore sample from Oman.

18

Early Metallurgy of the Persian Gulf

Geological and Archaeological Surveys in the Early 1970s The next phase of research into early metallurgy in southeastern Arabia did not occur until the 1970s, and involved the first significant archaeological and scientific study of the material remains of ancient smelting operations within Oman. During this period, the importance of southeastern Arabia to studies of the Gulf copper trade was first clearly demonstrated, through the discovery of evidence for copper production from the third millennium BCE onwards. This archaeological evidence came to light primarily through research programs conducted by the geological survey company Prospections Limited Oman (Goettler et al. 1976), by Harvard University (Hastings et al. 1975), and by the Institute for Human Palaeontology in Rome (Tosi 1975). Geological research in the region was undertaken by Prospections Limited Oman from 1973. Interestingly, geological survey for copper deposits in Oman was to a large degree inspired by Geoffrey Bibby's then recently published book, Looking for Dilmun (Bibby 1970; Goettler et al. 1976:43). One of the major approaches utilized in Prospection Limited's survey for copper deposits was the questioning of local inhabitants with regard to their knowledge of old smelting places in the mountains (Weisgerber 1991b:79). As a result, the investigations of Prospection Limited resulted in some important archaeological discoveries, including the remains of at least 44 ancient production sites. These sites were recognized primarily by the presence of slag produced by ancient smelting operations, estimated visually to range from "a few tons to, in one instance, more than 100,000 tons" (Goettler et al. 1976:43-44). Examples of slag heaps associated with early copper smelting in the region are illustrated in Figures 2.3-2.4. Nineteen deposits were estimated to have at least 1,000 tonnes of slag. The variations in the size of slag deposits at different smelting sites were thought t o reflect the fact that smelting operations at a newly discovered ore body were part of the prospecting process (Goettler et al. 1976:44). In this model, small slag heaps represented "test runs" in which the viability of an ore body had been assessed and found to be non-economic.

Figure 2.3. Slag heaps at Samdah, Oman (from Weisgerber 1978: PI. 12b).

Evidence for the extraction of copper ores was also recorded. Surface mining was recorded in the form of small pits and trenches, as well as larger "open" pits of up to 100 m wide, while shafts and adits of considerable depth were found at a number of sites. The overall impression gained by the geologists of Prospection Limited was that "a major effort involving extremely hard, highly organized work was mounted" in order to extract and process the copper ores (Goettler et al. 1976:45). Consideration was also given to the technology employed in the copper smelting and the types of

ores exploited. It was suggested that secondary copper minerals such as malachite, azurite and turquoise ( C U A ~ ~ ( P O ~ ) ~ ( O Hwould ) ~ - S have H ~ ~been ) the primary ores utilized. This supposition was supported by the fact that 23 of the 44 production sites were adjacent to workings in shear zones in basic intrusions, in which only secondary minerals were present (Goettler et al. 1976:46-47). It was thought that secondary ores would have provided a high-grade feed to the smelters, and would have been easily seen and separated by early miners due to their bright colors. Additionally, the major sulfidic ore found in Omani

Geology and Early Exploitation of Copper

19

Figure 2.4. Slag fields at Tawi 'Arja, Oman (after Weisgerber 1978: PI. 18a).

deposits, chalcopyrite, was generally found to be highly intermixed with other minerals in the ore body, and hence difficult to extract by hand sorting (Goettler et al. 1976:47). Native copper was regarded as occurring so rarely as to have been insignificant for early copper use in the region (Goettler et al. 1976:47). Establishing the periods of use of the mines and smelters located in the geological survey was considered of basic interest, but conclusions were difficult to draw and required the introduction of archaeological evidence. Goettler et al. (1976:45) suggested three main periods of exploitation: a pre-Islamic phase, a phase dating to the nineth to tenth centuries CE, and finally a phase dating to the fifteenth to sixteenth centuries CE. Workings of the pre-Islamic phase were considered, partly on archaeological evidence collected by the Harvard Archaeological Survey, to have been worked as early as 2500 BCE, possibly continuing into the second millennium BCE (Goettler et al. 1976:45-46). The later phases of extraction were determined through the analysis of pot-sherds from various smelting sites, and also through the radiocarbon dating of charcoal inclusions in slag samples (Goettler et al. 1976:46).

20

Early Metallurgy of the Persian Gulf

Evidence of third millennium BCE mining activities was also recorded by the Italian expedition to Oman (Tosi 1975) and by the Harvard Archaeological Survey (Hastings et al. 1975). The Harvard survey was not aimed solely at the discovery of sites related to copper production, nevertheless third millennium BCE sites with evidence of copper smelting were recorded at Wadi Samad 5, Batin 1, and Zahir 2-3 (Hastings et al. 1975:12 and Figure 2). Fieldwork by the Italian mission also generated discussion on ancient mining in the region, and Tosi and Piperno suggested that "surface mining in the deposits or the gathering of metal-bearing pebbles from the wadi beds probably prevailed over actual mining operations" (Tosi 1975:198). The evidence for third millennium copper smelting in the region was regarded by the Italian mission as very similar to midthird millennium material with which the authors were already familiar, from the site of Shahr-i Sokhta in Iranian Seistan (Tosi 1975:202). However, the reconstructions of smelting technology suggested by both the Italian mission and the Harvard team (Hastings et al. 1975:12) were speculative efforts unsupported by scientific analyses of the extant smelting remains.

Brief mention is made, in both archaeological and geological reports from the early 1970s, of the importance of these discoveries for the location of the land of Magan. A number of compositional analyses of ore was presented by Prospection Limited (Goettler et al. 1976:49-SO), in which the presence of nickel was demonstrated (particularly for deposits in shear zones in ultrabasic rocks), in support of the conclusions of Peake (1928) discussed above. In contrast, Hastings et al. (1975:l.S) noted that, although there was good evidence for the production of copper in the region in the third millennium BCE, at the time of their article there was no clear evidence for the export Omani copper in the Bronze Age. Indeed, the area was regarded by these researchers as "a scene of quiet well being untouched by the maelstrom of Mesopotamia or Iran" (Hastings et al. 1975:15). Sensibly, however, they allowed that excavation might change the reconstructions suggested by their survey data. Thus, the archaeological and geological work carried out in Oman between 1973 and 1975 was able to demonstrate significant evidence for ancient copper production in the region. Theories were proposed regarding the technologies and processes of copper smelting at various periods in the region's past, although archaeometallurgical and related analyses were extremely limited. Estimation of the periods of copper production also proved problematic, while calculations of the volume of copper production in the various periods of extraction were not possible due to this chronological uncertainty, in addition to the incomplete nature of survey and the lack of detailed archaeometallurgical analyses.

Analyses by the Centre National de la Recherche Scientifique (CNRS), France In the late 1970s and early 1980s, a number of archaeometallurgical studies were published by scholars from the Centre National de la Recherche Scientifique (CNRS), the Commissariat i1'Energie Atomique, and the Laboratoire de Recherche des Musies de France that included analyses of material from southeastern Arabia (Berthoud 1979; Berthoud et al. 1980, 1982; Berthoud and Cleuziou 1983). The articles represented an effort to characterize the evolution of alloying techniques in early western Asia (Berthoud et al. 1982), and

to scientifically determine the provenance of copper used in various regions bordering the Gulf in the fourth and third millennia BCE (Berthoud et al. 1980; Berthoud and Cleuziou 1983). Surprisingly, these were the first published analyses of copper-base objects from the Gulf since the work of Peake for the Sumerian Copper Committee in the 1920s. The provenance program was based on two series of compositional data: one on copper ores from various ancient mining regions in western and central Asia, the second on copper objects from Iran, Mesopotamia and southeastern Arabia (Berthoud and Cleuziou 1983:242). Berthoud et al. (1980:88; Berthoud and Cleuziou 1983:242-243) noted a great similarity in the composition of copper used in the mid-third millennium from the "Vase i la Cachette", late third millennium BCE copper objects from Ur, and Umm al-Nar Period objects from southeastern Arabia (Hili and Umm al-Nar Island), as well as distinct differences in the composition of copper produced in Iran and Oman. They concluded, amongst other things, that southern Mesopotamia and Khuzistan obtained their copper from southeastern Arabian sources at least by the Early Dynastic I11 period, and perhaps as early as the EDII period (Berthoud and Cleuziou 1983:243). The analytical approach of Berthoud (1979) has been questioned (Seeliger et al. 1985:642-643, note 74) on the grounds that the analyses were of an accuracy and precision insufficient to allow the stated conclusions of the work, and on the limited number of analyses used to characterize copper produced in different areas (Hauptmann 1987:209; Hauptmann et al. 1988:34). The claimed ability of the analyses to satisfactorily delineate between southeastern Arabian and Iranian ore sources has been particularly disputed. The limited nature of the ore database is particularly clear in some instances, for example in southeastern Arabia where analyzed ores contained arsenic levels of up to only 690 ppm, whereas objects from the region contained up to seven percent arsenic (Berthoud et al. 1982:45). Nevertheless, the French analytical program was important for providing the first characterization of the chemical composition of significant numbers of copper-base objects from

Geology and Early Exploitation of Copper

21

southeastern Arabia, and for focusing on material from the northern part of the Oman Peninsula, in the modern U.A.E. The subsequent work by the German Mining Museum, to which we will now turn, has dealt almost exclusively with material from more southerly regions, in the modern day Sultanate of Oman.

German Mining Museum Project in Oman The work in Oman of the German Mining Museum began in January 1977, as a collaboration with the Oman Department of Antiquities and scholars from the University of Naples (Costa 1978:9). It was agreed at that time that a German expedition to the region was to be entrusted with all studies concerning archaeometallurgy (Costa 1978:13), and important field seasons were conducted by this expedition in the late 1970s and early 1980s (Weisgerber 1978a, 1978b, 1980b, 1980c, 1981, 1987, l 9 8 8; Hauptmann and Weisgerber 1980; Hauptmann 1985, 1987; Hauptmann et al. 1988). German research in the Sultanate of Oman with a strong, though far from exclusive, emphasis upon copper production continues to this day (e.g. Yule 1996; Yule and Weisgerber 1996; Prange et al. 1999). The early survey work of the German team was able to build upon the results of the geological survey undertaken by Prospection Limited in the early 1970s (Weisgerber 1978a:20), and was particularly focused upon the importance of Oman and southeastern Arabia in general as a potential location of Magan (e.g. Weisgerber 1983, 1984, 1991b). This research focus was inspired by Geoffrey Bibby's Looking for Dilmun (Weisgerber 1991:76), and remains a hallmark of more recent archaeometallurgical work on Omani material by the German team (Prange et al. 1999). Their initial research centered upon mining sites in the hinterland of Sohar, at Lasail, Bayda, 'Arja and Samdah, and on the third millennium BCE site of Maysar 1 in the Wadi Samad that had been discovered by the Harvard Archaeological Survey (Figure 2.2; Hastings et al. 1975; Weisgerber 1978a; see also Lamberg-Karlovsky 2001:xxxiv-vi). It was soon realized that the vast majority of the more than 150 mining and smelting sites that they recorded were worked in the Islamic period (Weisgerber 1980b:68; l98Oc: 115),

22

Early Metallurgy of the Persian Gulf

although it was recognized that evidence for earlier periods of production at these sites could occasionally be found (e.g. Weisgerber 1980b:lOl; 198l:l87-190). The situation encountered by the German team in Oman is paralleled by that in Cyprus, where evidence for significant Bronze Age production is often obscured or destroyed by later Phoenician and Roman workings (Weisgerber 1982:28). Over the course of four field seasons in the Sultanate of Oman, the German Mining Museum expedition was able to provide an outline of the periods of copper production in the region (e.g. Weisgerber l 9 8 1:Abb. 4), characterize the development of copper mining and extraction technology (e.g. Hauptmann 1985), estimate the volume of copper produced in some historic and prehistoric periods (Hauptmann 1985:108-1 O9), and begin to address the social and economic implications of this industry for southeastern Arabia (e.g. Weisgerber l98Oc: 117-1 18). Additionally, as the archaeology of southeastern Arabia was so poorly known in the 1970s, the fieldwork of the German mission was crucial in the development of a basic chronological framework for discussion of the archaeology of the region (Weisgerber 1982:29). As such, the results of these investigations rank as amongst the most important contributions to the archaeology of southeastern Arabia by a single research group. The archaeometallurgical results of this research are summarized below. Periods of Production It is estimated that there are approximately 50 major copper deposits and more than 100 minor deposits in the mountains of northern Oman (Weisgerber 1983:270). The majority of these ore-bodies show signs of exploitation in the Islamic period, however multi-period exploitation has been found to be commonplace (Weisgerber 1983:274) and the earliest period of copper exploitation in the region can be traced back to the third millennium BCE. The German mission in Oman has provided a reasonably secure chronological basis for the discussion of various periods of copper production in southeastern Arabia based upon typological analyses of excavated material (e.g. Weisgerber 1987:Figure 76; Hauptmann 1985:38-40) and programs of scientific dating, notably radiocarbon and thermoluminescence (e.g.

3

1OOm

50 I

1

I

l

l

'

,

,

'

)

Figure 2.5.The settlement at Maysar 1, the mining area M2,and the cemetery M3, in Oman (from Weisgerber 1983: Figure 2).

Geology and Early Exploitationof Copper

Weisgerber 1981:250-251 and Abb. 95; Yule and Weisgerber 1996:141). Nevertheless, some limitations in the chronological attribution of smelting sites do exist, and their effect on archaeological theories are discussed in the relevant sections below. As outlined below, evidence for local copper production in the Hafit Period is entirely circumstantial, and includes the presence of copper objects in Hafit graves and in the upper levels of fifth-third millennium BCE shell-middens at Wadi Shab GAS1, Ra's al-Hamra and Ra's al-Hadd. Copper production sites of this period are not reported by the German researchers, however an early but undated "trial and error" phase of copper production from Maysar 1 is thought to represent copper extraction prior to the Bliitezeit of production at the site in the late third millennium BCE (Hauptmann l985:ll3). Copper "droplet-slags" from this period at Maysar 1 are extremely high in copper, suggesting an inefficient extraction of metal which may have been carried out in open crucibles (Hauptmann 1985:92). A second smelting site recorded at al-Batin has been dated by thermoluminescence to ca. 2500 BCE, i.e. a few centuries before production at Maysar 1 (Yule 1996; Yule and Weisgerber 1996:141). The slag from al-Batin is typologically distinct from that produced later in the Urnm al-Nar Period (Yule and Weisgerber 1996:l 4 l ) , but little more can be said about the technology of copper extraction in southeastern Arabia in the early-mid third millennium BC. Archaeological evidence suggests an expansion of production from the later third millennium BCE. Sites of this period are generally referred to in German reports as "Bronze Age (third to second millennium)", but are clearly regarded as dating to the Urnm al-Nar Period rather than the Wadi Suq Period (Hauptmann 1985:113-115). At least twenty sites with evidence for copper extraction are listed by Hauptmann (1985:116-117), some of the most important being Maysar 1, Assayab, Bilad al-Maaidin, Wadi Salh 1 and Tawi-Ubaylah (Weisgerber l 9 8 1:l87-190; Hauptmann et al. 1988:35). Up to 4,000 tonnes of slag are recorded at individual Bronze Age smelting sites, although the reconstructions of smelting technology depend mostly upon material excavated from the late Urnm al-Nar Period settlement at Maysar 1 (Figure 2.5), which pro-

24

Early Metallurgy of the Persian Gulf

duced only about 100 tonnes of slag (Weisgerber 1980b; 1981; Hauptmann 1985:92-95). Although only around 20 sites with Bronze Age slag were recorded by the German team, they envisage that contemporary copper extraction would have taken place at many, perhaps most, of the known copper deposits in the region (Weisgerber 1984:198; Hauptmann l985:95). The evidence from many sites may have been completely covered or destroyed by later mining activities, particularly during the early Islamic period. The association of Urnm al-Nar Period burial cairns with numerous extraction sites showing no signs of Bronze Age exploitation is regarded as suggestive of the widespread distribution of early mining and smelting activities in the region (Weisgerber 1978a: 19-20). However, this hypothesis is unproven. The combined results of archaeological survey, excavation and archaeometallurgical analysis have allowed a reconstruction of the volume of copper produced in southeastern Arabia in the second half of the third millennium BCE. Based on the amount of Bronze Age slag recorded at smelting sites in Oman (ca. 10,000 tonnes) and an experimentally calculated slag to copper ratio of between 5:l and 10:1, Hauptmann (1985:108) was able to arrive at a minimum figure for Urnm al-Nar Period copper production of between 1,000 and 2,000 tonnes. Given the likelihood that many Urnm al-Nar Period smelting sites were destroyed by later mining activities, a conservative estimate of total production of between 2,000 and 4,000 tonnes was suggested (Hauptmann 1985:108). Extensive evidence for copper use in the Wadi Suq Period exists in the form of copper-base grave goods (Velde 2003:109-112; Weisgerber 1991a; Potts 1990a:252-253), and primary copper production is thought by some scholars to have continued in this period, perhaps at levels similar to that in the preceding Urnm al-Nar Period (e.g. Velde 2003: 109; Weisgerber 1988:285). However, it must be stressed that the use of copper objects is at best circumstantial evidence for contemporary primary copper extraction (contra Velde 2003:109), given the fact that much of the copper used in the Wadi Suq Period could have been obtained from robbing the richly-furnished Urnm al-Nar Period graves that covered the peninsula, or through trade (e.g.

Weisgerber l 9 8 1:2l9). In contrast to the third millennium or the Iron Age, very few Wadi Suq Period settlements are known (Velde 2003:Table 1; Carter 1997), and none show evidence for primary copper smelting such as that seen in the Wadi Fizh or at Maysar 1. The only clear evidence for contemporary primary production is the presence of copper mines on Masirah Island, which have been radiocarbon dated to approximately 1800 BCE (Weisgerber 1988:note 7; unfortunately details of calibration are not given). In addition, copper smelting in this period has been hypothesized based upon the presence of Wadi Suq type tombs in Wadi Salh and Wadi Samad in areas adjacent to copper smelting refuse, although the contemporaneity of the tombs and the smelting practices is far from certain (Weisgerber 1988:285 and note 7). No published reports exist regarding the volume of slag of Wadi Suq date from these sites, and the technological basis of production remains unknown (Yule and Weisgerber 1996: 144). If it is maintained that significant copper production continued into the second millennium BCE in Oman, the continued non-appearance of Wadi Suq extraction and smelting sites must be explained through either: 1) incomplete survey; 2) near-complete destruction or obscurement by later production, or; 3) problems in the recognition or dating of this material on archaeological sites (cf. Hauptmann 1985:95). With fieldwork by the German mission continuing into the 1990s, the likelihood of incomplete survey as an explanation for the dearth of Wadi Suq-related smelting sites is quickly diminishing (cf. Weisgerber 1988:285). Likewise, the discovery of Bronze Age and Iron Age smelting remains amongst extensive early Islamic operations at numerous sites suggests that the second factor is unlikely to have completely compromised the search for second millennium smelting remains. With regard to the third possibility, Velde (2003:109) has suggested that the "scanty knowledge" of second millennium material culture at the time the German surveys were undertaken may have affected the recognition of Wadi Suq Period smelting sites. However, even the early publications of the German team (e.g. Weisgerber 1981:219) show awareness of the second millennium funerary material recovered by Frifelt (1975a) in the Wadi Suq and by the French excavations at the Hili-8 settlement (Cleuziou

1980, 1981). The non-recognition of this material by the German researchers, therefore, seems unlikely. Furthermore, the continuation of the German fieldwork into the late 1990s, when 2nd millennium material culture sequences were much more clearly known, suggests that the continued scarcity of Wadi Suq Period smelting sites is unlikely to be explained by non-recognition of diagnostic material remains. It is the chronological range of putative "Bronze Age" smelting sites which may require closer scrutiny. The ceramic material from Bronze Age smelting sites located within settlements (e.g. Maysar 1, Wadi Fizh 1) shows that they date exclusively to the later Umm al-Nar Period (e.g. Weisgerber 1981:Abb. 17). However, most "Bronze Age" smelting sites are not associated with settlement remains and, consequently, lack ceramics. These sites are thus dated by comparison to Maysar 1 slag typologies rather than to ceramic typologies, and could feasibly cover a greater time period than Maysar 1 itself. Specifically, such sites may have resulted from primary copper production well into the Wadi Suq Period. Clearly, detailed archaeometallurgical investigations are required at such extraction sites, and in areas such as Masirah Island where some evidence for Wadi Suq Period copper production does exist. Until such work has been undertaken, reconstructions of the volume and periodicity of local copper production in the second millennium BCE, such as presented by Weisgerber (1981:Abb. 4) and Hauptmann (1985:Abb. l),remain conjectural (see below). An increase in copper production has been hypothesized for the Iron Age in southeastern Arabia, as a result of the first exploitation of the massive sulfide deposits of the upper extrusive sequence of the Semail Ophiolite (Weisgerber l 9 8 8:286). At least twenty archaeological sites related to Iron Age copper extraction are recorded (Hauptmann 1985:116-1 17), including large-scale mines (Weisgerber 1987:150), slag fields, and settlements for which copper processing was an important economic activity (e.g. Costa and Wilkinson 1987:99-103). Some of the more important sites include Lasail (Weisgerber 1987:150), Raki (Weisgerber 1988:286; Yule and Weisgerber 1996:142-144; Weisgerber and Yule 1999:109-116 and Figure 12) and 'Arja site 132 (Weisgerber 1987:l48), although analysis of archaeomet-

Geology and Early Exploitation of Copper

25

allurgical finds is minimal and technological details of Iron Age smelting processes remain largely unknown (Yule and Weisgerber 1996: 142). Evidence for technological change within the Iron Age is provided by stratified slag deposits from Raki, which show two different slag types, and which are at least partially datable to ca. 1100-800 BCE by radiocarbon determinations (Weisgerber and Yule 1999:115). Iron Age sites face, in general, the same problems of preservation as Bronze Age sites. They are very prone to destruction by early Islamic activities, particularly as they concentrated upon the exploitation of the same ore bodies (massive sulfide deposits) as mined in the Islamic period, and their original number was undoubtedly greater than that observed through modern survey and excavation. As for the Bronze Age, Iron Age copper extraction at a number of sites has been postulated on the basis of nearby Iron Age burial cairns (e.g. Yule and Weisgerber 1996:142) Although no published estimates exist for the amount of copper produced in the Iron Age, a considerable increase from preceding Bronze Age output is clear, judging from the volume of surviving extraction waste. Single smelting sites with as much as 45,000 tonnes of Iron Age slag have been recorded (Hauptmann 1985:107, 116-117; cf. Yule and Weisgerber 1996:142-144), and a minimum production of 7,000-20,000 tonnes can be confidently suggested, based on Hauptmann's (1985:108-109) calculations for the massive sulfide extraction of the early Islamic period and the presence of more than 80,000 tonnes of Iron Age copper slag at the sites of Raki 2 and Tawi Raki 2 alone (Hauptmann 1985:ll6-117). The great quantity of copper-base objects from Iron Age tombs in southeastern Arabia, for example Qidfa (Im-Obersteg 1987; Corboud et al. 1988) and IbriISelme (Weisgerber l 9 8 1:232-233; Yule and Weisgerber 2001), provides additional circumstantial support for the large-scale local production of copper in the Iron Age. A significant gap seems to exist in the evidence for copper production in southeastern Arabia between the mid first millennium BCE and the mid first millennium CE. Very few radiocarbon dates exist for smelting operations from the first millennium BCE (see Weisgerber 1981:Abb. 95), as sites were dated by the presence of

26

Early Metallurgy of the Persian Gulf

diagnostic Iron Age or "Lizq Period" ceramic sherds. Pottery of the later first millennium BCE and early centuries CE in Oman (the so-called "Samad Period") has not been recovered from any smelting sites, and the next evidence for production is provided by some slag samples from 'Arja which yielded late pre-Islamic radiocarbon age ranges of the fifth to seventh centuries CE (Weisgerber 1980b:Table 2; Weisgerber 1987:148-149 and Table 14). At present, copper processing of this period is recorded only at two sites in the vicinity of the Bayda gossan, and at Raki (Yule 1996:176), although it is thought that late Sasanian exploitation of other copper mines in the region is likely (Weisgerber 1987:149). Copper production in southeastern Arabia reached its greatest extent in the early Islamic period, and the enormous quantities of waste material generated by these activities have obliterated most traces of earlier activity. Almost all the known copper deposits of the Oman Mountains were worked at this time (Weisgerber 1980:115; Weisgerber 1980:68; Weisgerber 1983:270). Production was found to have peaked in the ninth and tenth centuries CE, based upon ceramic finds and numerous radiocarbon analyses (Weisgerber 1991b:80-81), with quantities of slag of up to 100,000 tonnes reported from Lasail. Most important sites in this period were located in the hinterland of Sohar, which provided the trading outlet for the enormous surplus of production (Whitehouse 1979:874-875; J.C. Wilkinson 1979:892), and included Samdah (ca. 40,000 tonnes of slag), 'Arja and Bayda (Hauptmann 1985:116-117). Inland sites such as Raki and Wadi Salh were also important copper sources (Hauptmann 1985:116-117). Because of the large quantities of available archaeological evidence, a great deal is known about the technological aspects of copper production in this period and, to a lesser extent, the organization of production at the mining sites and the economic regulation of the trade in this material through Sohar (J. C. Wilkinson 1979:892; Weisgerber 1987:144). Around 600,000 tonnes of early Islamic slag have been recorded in Oman and calculations of production during this period, based upon a slag to copper ratio of between 12.5:l and 10:1, suggest a total output of between 48,000 and 60,000 tonnes of copper (Hauptmann 1985:108-109).

Figure 2.6. Evidence for Umm al-Nar Period mining at Maysar 2, Oman (from Weisgerber l98Ob: Abb.48).

There appears to be a hiatus between the largescale copper production of the early Islamic period in southeastern Arabia and subsequent production, the first evidence for which dates to the twelfth century CE (Weisgerber l98Oc: 118-1 19; Weisgerber l 9 8 1:Table 2). Copper extraction from the twelfth century onwards is represented by much less archaeological evidence, reflecting drastically reduced levels of production and lower levels of technological understanding in comparison to earlier smelting operations (Hauptmann 1985:103-107). Approximately forty extraction sites dating from the twelfth to nineteenth centuries CE are known from German surveys and excavation in Oman, some of the most important being Abu Zainah and Tawi 'Arja (Hauptmann 1985:107, 116-117). Copper production (whether continuous or not) over these seven centuries produced a total of approximately 25,000 tonnes of slag which, at a ratio of slag to copper of between 6.7:l and 8.3:1, represents a total production of 3,000-3,700 tonnes of copper (Hauptmann 1985:109).

Mining In the Umm al-Nar Period, evidence of techniques used in the mining of copper ores comes primarily from sites in the vicinity of the settlement of Maysar 1 (Weisgerber 1983:271). The nearest mining site, Maysar 2 (Figure 2.6), is less than 100 m from Maysar 1 and contains evidence in the form of deep "surface scratches" for the extraction of approximately 10,000 m3 of ore and gangue through open cast mining (Weisgerber 1980a:77; Weisgerber 1980b:89 and Abb. 28). Other mine sites of this period, Maysar 16 and Maysar 49, exhibit evidence for similar extraction techniques, although at Maysar 16 deeper mining is suggested by the presence of two infilled shafts (Hauptmann 1985:91). In the vicinity of Maysar, the most frequently mined copper deposits of the third millennium BCE were the small, fault-controlled stock-work ores located in basic and ultrabasic rocks of the ophiolitic upper mantle sequence or the lower cumulate sequence of the ophiolite crust (Weisgerber 198010389; Hauptmann 1985:Abb. 6). These ores, although of a sulfide basis like all copper

Geology and Early Exploitation of Copper

27

ores in southeastern Arabia (Weisgerber 1983:270), had intense areas of secondary mineralization, including such species as malachite, chrysocolla, brochantite and antlerite ( C U ~ S O ~ ( O HThe ) ~ )ores . selected had low proportions of iron sulfide (pyrite) and copper-iron sulfide (chalcopyrite), and high copper contents of five to 56 percent (Hauptmann 1985:91), both of which are important considerations for early smelting technology. Significantly, copper ores from such deposits are likely to have different mineralogical characteristics to massive sulfide ores from the extrusive sequence. In particular, nickel (Ni),arsenic (As)and cobalt (CO)levels are likely to be higher in the types of deposit exploited at Maysar, as mineral species containing these elements are often intergrown with the local copper ores (Hauptmann et al. 1988:35). As noted above, very little is known about copper mining in the following Wadi Suq Period. Mines dated to ca. 1800 BCE by radiocarbon analysis have been recorded on Masirah Island (Weisgerber 1988:285), but no further details of mining techniques or the ores extracted are available. Similarly, although smelting remains of Iron Age date are known from about 20 sites in Oman, little has been written on mining techniques of this period. The Iron Age is said to represent the first period in which the ophiolitic massive sulfide deposits were exploited for their copper content (Weisgerber l 9 8 8:286), and Iron Age mining activities are likely to have been significantly destroyed by early Islamic operations in the region (e.g. Weisgerber 1987:148). Evidence from the site of Lasail suggests that an enormous open cast mining area in the deposit gossan, up to 30 m deep, may date to the first millennium BCE (Weisgerber 1987:150). The most extensive evidence for mining activities in southeastern Arabia comes, unsurprisingly, from the early Islamic period. As noted by Weisgerber (1980c:115), mining techniques in Oman were shaped by the geological nature of copper deposits in the ophiolite. The most intensely mined deposits in Oman were those in which significant amounts of copper remained in the gosSan. In some cases, the gossan itself was nearly completely removed in a procedure whereby the "weathered and concentrated ore-body was dug in front, the ore was taken out at the spot, and the waste deposited behind" (Weisgerber l98Oc:ll6). Sites such as Assayab, Mullaq

28

Early Metallurgy of the Persian Gulf

and Samdah show evidence for the removal through mining of large amounts of the original gossan (Weisgerber 1980c:116). For other deposits, underground mining using galleries, shafts and pits is evidenced. Rectangular shafts of ca. 80 X 60 cm (Weisgerber 198013366-67 and Abb. 6) are typical of mining operations of this period at sites such as Bayda, Tawi Ubaylah, Lasail and al-Sayab, and inclined shafts and galleries have been found at depths of up to 87.5 m (Weisgerber 1987:150 and Figure 67). Archaeological evidence indicates that these galleries had roof supports of acacia wood and roofs of date palm matting, lighting was provided by terracotta oil lamps, and ore and gangue were removed through the use of lifting devices such as windlasses as well as by hand (Weisgerber 1987: 150-15 1, Figure 68). For all periods of mining activity in southeastern Arabia, the discovery of metallic extraction tools is unlikely because of the sulfidic nature of the ores, which generated an acidic environment within the mine deposits that would have destroyed any remaining metal artifacts. As for the Iron Age, the most important ores sought by the early Islamic miners were mixed iron and iron-copper sulfides (Hauptmann 1985:95), as well as the extensive low-percentage copper mineralization in the gossans of the massive sulfide deposits (Hauptmann 1985:107-108, Abb. 85). Analyses of slags produced in this period indicate that relatively little gangue material was included in the furnace charge, suggesting that either the massive form of the ore made sorting easy or that ore concentration processes prior to smelting were more thorough in the early Islamic period (Hauptmann 1985:95). The copper content of the concentrated sulfidic ores used for smelting was in the range of 15-20 percent (Hauptmann 1985:95). The mining of copper ore is not thought to have taken place to any significant extent in the later Islamic period in Oman (Hauptmann 1985:103). Copper production in the twelfth to nineteenth centuries CE is thought to have relied on the reworking of earlier Islamic and perhaps pre-Islamic slag, as evidenced by the pits dug into many slag heaps of these periods at sites where later Islamic workings are known (Weisgerber 1978a:19; Weisgerber 1980b:73; Weisgerber 1987:160-161; Hauptmann 1985:103).

Figure 2.7. Hammer and anvil stones from Maysar l , Oman (from Weisgerber 1978: PI. 1 1c).

Ore Concentration In all periods of copper production in southeastern Arabia, ore crushing and concentration was carried out using hand held hammerstones and large stone anvils. Numerous examples of such objects are known from third millennium BCE levels at Maysar 1 (e.g. Weisgerber 1978a:Pl. l l c ) as well as at sites of the Islamic period such as Samdah and Tawi 'Arja (e.g. Weisgerber 1978a:Figure 9, P1 15b, 21d; Weisgerber 1987:152-153). Anvil stones are usually identified by the presence of multiple concavities caused by repeated hammering (e.g. Weisgerber 1978a:Pl. 21c), and smaller cubic hammerstones often show evidence for use of all six faces during ore crushing and concentration activities (e.g. Weisgerber 1978a:Figure 10). There is little or no variation through time in the typology of the hammer and anvil stones used in southeastern Arabia, and such items are thus chronologically non-diagnostic when seen at smelting sites in the region. Maysar 1 examples are illustrated in Figure 2.7.

Smelting The evidence for copper smelting in southeastern Arabia in the third millennium BCE comes primarily from the Maysar 1 settlement site excavated by the German team. The archaeological remains from this site have been well documented in a number of publications (e.g. Hastings et al. 1975; Weisgerber 1978a; 1980b; 1981), and are significant for the presence of large amounts of material such as ore, slag, furnace fragments and bun-shaped copper ingots which indicate the primary extraction of copper at the site. This range of material, in addition to the evidence from the nearby extraction site of Maysar 2, has allowed a detailed reconstruction of the smelting technology used at Maysar 1 in the third millennium BCE (Hauptmann 1985; Hauptmann et al. 1988). The earliest copper production at Maysar 1 occurred in the first half of the third millennium BCE, although the archaeometallurgical evidence of these operations is extremely limited. Very small smelting furnaces or crucibles were used, although no evidence of their actual form remains, and secondary oxides and sulphur-bearing

Geology and Early Exploitation of Copper

29

Figure 2.8 Fragments of the base of a smelting furnace from Maysar 1, Oman (from Weisgerber 1983: PI. 9).

copper minerals were processed (Hauptmann 1985:92). Only moderate smelting temperatures were reached, the reduction of copper ores to metal was incomplete and the separation of copper from slag was poor, leading to slags with very high copper contents of up to 30 percent (Hauptmann 1985: 113). The nature of the analyzed slags of this period from Maysar 1 strongly suggests that these operations represent a "trial and error" phase of copper production at the site Later Umm al-Nar Period smelting at Maysar 1 utilized a mixture of the secondary ores mined at sites such as Maysar 2, Maysar 16 and Maysar 49, including malachite and chrysocolla as well as sulfur-containing ores such as brochantite (Hauptmann et al. 1988:36,71-72). No roasting of the ores was undertaken prior to smelting operations (Hauptmann et al. 1988:36, 71-72). These ores were mixed with charcoal produced from local tree and shrub species (e.g. acacia, prosopis and zizyphus), and iron ores such as haematite (Fe203)and limonite were used as fluxes (Hauptmann et al. 1988:37). The iron-rich fluxes were necessary as the copper ores used were intensively intergrown with siliceous country rock,

30

Early Metallurgy of the Persian Gulf

not all of which could be removed during ore concentration processes. The surviving furnace fragments from Maysar 1 (see Figure 2.8) indicate that the smelting furnaces in use at the site were made of leaned clay, and had a diameter of 40-50 cm, a height of approximately 40 cm and a volume of between 10 and 15 liters (Weisgerber 1983:274; Hauptmann 1985:92). Exact details of the forced air supply to the furnaces are not known, although fragments of tuygres have been recorded at the site and the use of bellows is regarded as likely (Hauptmann 1985:92). The large number of furnace fragments at Maysar 1 in comparison to the quantity of slag has suggested to the German team that smelting furnaces of the third millennium BCE at Maysar 1 had a short lifespan, and were frequently rebuilt (Hauptmann 1985 :92). During the one-step smelting process, both copper and relatively pure matte (mostly Cu2S, with low levels of iron) were produced. Copper was precipitated within the furnace by reduction of the ore in the presence of charcoal and also by the principle of the "roast reaction", in which matte is oxidized to cuprite (Cu20),which then reacts

with the remaining matte to produce metallic copper, as follows (Hauptmann 1985:94): I. 2Cu2S + 3 0 2 2Cu20 + 2S02+ 2. Cu2S + 2Cu2O 3 6Cu + SO2+ The oxide-sulfide mineral interaction central to Hauptmann's roast reaction is thus akin to the concept of "CO-smelting"investigated by a number of archaeometallurgists (e.g. Lechtman and Klein 1999; Rostoker and Dvorak 1991; Rostoker et al. 1989), which will be discussed later in this volume with regard to the production of arsenical copper alloys. Studies of the slag and furnace fragments from Maysar indicate that temperatures in the range 1,150-1,200 degrees C were achieved in the furnaces (Hauptmann et al. 1988:3640). However, the viscosity of the resulting slag/matte/copper mix within the furnace was relatively poor, meaning that separation of these elements was sometimes less than ideal (Hauptmann et al. 1988:40). Slag was tapped from the smelting furnace in a viscous state, and thus frequently contained high levels of residual copper (see Hauptmann 1985:119-120). Examples of the different types of slag found at Maysar 1 are illustrated in Figure 2.9. At the end of the smelting process, the newly-won copper and matte were separated by mechanical means (Hauptmann 1985:1l4), although high levels of sulfur and iron in analyzed copper samples from the region indicate that significant amounts of matte can remain in copper produced by this process (Hauptmann et al. 1988:37; see also Rostoker et al. 1989:Figures 6-7). Following mechanical separation, the small copper lumps produced by the primary smelting operation were remelted together in ceramic crucibles and finally cast into planoconvex ingots in appropriately-shaped cavities dug into the sandy floor of the copper workshops at Maysar 1 (Weisgerber and Yule 2003:4849) without being further refined (Hauptmann 1985:93-94). There is no clear evidence from Maysar 1 to indicate that the matte produced during primary smelting was further processed into metallic copper, although this is envisaged (Hauptmann 1985:Abb. 74; Hauptmann et al. 1988:37). The total production of copper in the settlement at Maysar 1 is thought to have been relatively small, and probably for domestic use (Hauptmann 1985:114). In comparison, much larger contemporary extraction and smelting sites such as Wadi Salh 1and Tawi Ubaylah have been recorded in Oman, suggesting that production on a larger

o

Gasblasen

W Kupferstein Kupfer

Figure 2.9. A slag typology for Umm al-Nar Period copper production at Maysar l , showing (A) large tapslags, (B) plate-like tapslags with negative impressions of mixed copper-matte concentrations on the base, (C) thin tapslags or "plate-slagsyand (D) droplet-slags (from Hauptmann 1985: Abb. 16).

scale may also have occurred in southeastern Arabia in the Umm al-Nar Period (Hauptmann 1985:34,95,114). This issue is further investigated below. Regardless of the scale of production activities, copper extraction at all known sites seems to reflect a similar technological basis to that seen in the settlement metallurgy of Maysar 1 (Weisgerber 1981:210). In contrast to the Umm al-Nar Period, very little is known regarding Wadi Suq or Iron Age smelting technology in southeastern Arabia. Slag or other extraction debris of Wadi Suq date has not been recorded by the German mission. Although more than twenty sites with evidence for Iron Age smelting have been recorded (see Figure 2.1 O), the "blocky black slag with fragments of brick-red lining on the outside" and the "silvery gray" tapslags (see Figure 2.11) which are characteristic of Iron Age smelting operations remain largely unanalyzed (Weisgerber 1987:148; Yule and Weisgerber 1996:144; cf. Hauptmann 1985:123). Iron Age smelting furnaces seem to have been excavated in areas of soft ground, and used over more than one smelting operation, however very few other technical details have been given (Weisgerber 1987:148). During the HellenisticISamad period in southeastern Arabia, the possibility of small-scale copper smelting in crucibles within settlements is suggested by excavated material from Mleiha, in the U.A.E. (Ploquin and Orzechowski 1994:30-32).

Geology and Early Exploitation of Copper

31

Figure 2.10. lron Age smelting remains from Oman, including hammer stones and slag (from Costa and Wilkinson 1987: PI. 51).

Figure 2.1 1 lron Age copper slag fromlArja in Oman (after Weisgerber 1978: PI. 16a).

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Early Metallurgy of the Persian Gulf

The next major smelting operations in the region are those undertaken in the early Islamic period, in the 9th and tenth centuries CE. These operations have left vast quantities of archaeometallurgical remains at extraction sites in southeastern Arabia, and as a result are very well studied and characterized (Hauptmann 1985). As noted above, predominantly massive sulfide ores were exploited at this time, and a complicated and relatively advanced extraction technology was developed to deal with the primary, unweathered ores of pyrite, chalcopyrite and bornite (e.g. Hauptmann 1985:107-108, Abb. 79). The extraction process in the early Islamic period is best conceived of as a complicated process involving repeated stages of alternating roasting and smelting operations (Weisgerber 1987:153; see also Rostoker et al. 1989:70-72 and Figure 1). Poor quality ores would require more roasting stages than better quality ones, and historical evidence from sixteenth century CE Europe suggests that the total roasting time for the ores could have approached one month (Hauptmann 1985:96).

The ores were roasted in a series of stone- and mortar-lined pits, usually about l m in diameter, which were dug into hill slopes at the production sites (Weisgerber 1980b:Abb. 7). Subsequently, they were smelted in shaft furnaces dug into rocky hill slopes, often behind and above roasting installations, in the vicinity of the mines themselves (Weisgerber 1987:154). Early Islamic roasting ovens and smelting furnaces have been excavated at a number of sites in Oman and the U.A.E., such as Lasail, Bayda and 'Arja and Wadi Madhab, and show a great degree of structural similarity across the region. Each smelting operation produced 20-50 kg of tapslag (e.g. Weisgerber 1978a:Figure 2) and 5-6 kg of copper matte containing 50-60 percent copper, which would have separated by density in the tapslag pit at the front of the furnace (Hauptmann 1985:114; see also Franklin et al. 1976). Following initial smelting, the refined copper matte, separated mechanically from the iron-rich slag, would have been roasted and re-smelted a number of times before finally being reduced to metallic copper (Hauptmann 1985:Abb. 79). The smelting furnaces used in southeastern Arabia in the early Islamic period were relatively robust, as they were used for significant periods of time and occasionally rebuilt (Weisgerber l987:156). The location of the furnaces seems to have been changed when too much slag built up in the direct vicinity, and so individual slag heaps from this period tend not to exceed 6,000 tonnes (Weisgerber 1987:156). Following the century or so of early Islamic smelting in southeastern Arabia, there is a gap in archaeological evidence for copper extraction (see above) followed by the introduction of completely new and technologically inferior smelting techniques in the twelfth to nineteenth centuries CE. Indeed, slags of this period from such sites as Tawi 'Arja and Abu Zainah were initially thought to represent the remains of prehistoric smelting operations due to their low technological standard (Weisgerber 1978b:29-30). Radiocarbon analyses of charcoal inclusions on the slags soon indicated their relatively recent age (Weisgerber l 9 8 1:Table 2). As noted above, there seems to have been little mining of copper ores at this time, and the basic smelter feed consisted of recycled early Islamic slag with high

matte content and some iron oxides and secondary copper minerals from early Islamic refuse piles (Hauptmann 1985: 103-1 04). The smelting furnaces used were bowlshaped and were partly dug into the ground (Hauptmann 1985:Abb. 82). A small clay superstructure, without a chimney shaft, extended above ground (Hauptmann 1985:104). Slag and matte were not tapped from these furnaces, but rather were allowed to solidify after smelting. This resulted in a large slag cake with a copper matte "ingot" at its base which was extracted by destroying the furnace superstructure and digging the remains from the ground (Weisgerber 1987: 159). Each smelting operation therefore required the construction of a completely new furnace, usually in the vicinity of previous examples, leading to the characteristic thin and dispersed nature of the bowl-slag fields of this period (Weisgerber 1987: 159). The slag and matte would have been separated by mechanical means. No evidence regarding the further treatment of the copper matte produced in twelfth to nineteenth century CE smelting operations has been recorded at any archaeological sites in Oman, so the final stages in the production of metallic copper at this time remain unknown (Hauptmann 1985:107).

Periodicity in Copper Production in Prehistoric Southeastern Arabia As described above, archaeometallurgical research regarding the chronology of copper production in Oman indicates that mining and extraction processes went through a number of periods of low or negligible output. An expression of this variability is given in Weisgerber's (1981:Abb. 4 ) summary of early German work in the region, which suggests a significant reduction in copper production in the second millennium BCE, and a complete lack of production between ca. 500 BCE and 800 CE, and ca. 1200-1800 CE. Although these exact ranges are modified in more recent publications (cf. Weisgerber l 9 8 8:285 on Wadi Suq mining; Weisgerber 1987: 148-149 on Sasanian workings; Hauptmann 1985:109 for twelfth to nineteenth century workings), copper production in Oman still appears to exhibit a distinct periodicity. The factors contributing to such variations in copper production in the Bronze and Iron Ages are discussed in this section.

Geology and Early Exploitation of Copper

33

Figure 2.1 2 Periods of copper production in southeastern Arabia. Part a) after Hauptmann (1985: Abb. 1). Part b) showing average copper production (tonneslyear)for the regions based upon the calculations of Hauptmann (1985: 115) and data in Batchelor (1992:Table 1). Data: Umm al-Nar Period production = 4,000 tonnes, duration = 400(min.)700(max.) years. Iron Age production = 10,000 tonnes, duration = 500(min.)-1,00O(max.) years. Early Islamic production = 60,000 tonnes, duration = 100 years.Twelfth-nineteenth century CE production = 3700 tonnes, duration = 700 years. Modern production = 107,200 tonnes from 1983-1990.

The summary of periods of production given by Hauptmann (1985:Abb. 1)is presented in Figure 2.12(a). The diagram is admittedly schematic, but nevertheless unintentionally suggests that copper production occurred at similar levels in the Umm al-Nar Period, the Iron Age, the early Islamic Period, and the modern period of the Oman Mining Company. More problematically, the diagram intentionally suggests that these levels of production were much higher than those of the second millennium BCE and the twelfth-nineteenth centuries CE. A rough guide to the levels of copper production in the region is provided by averaging estimations for total production in each period over the duration of the period, as is presented in Figure 2.12(b). This is a graph of the average copper production (tonneslyear) in each period, based on the production volumes determined by Hauptmann (1985:115) and data in Batchelor

34

Early Metallurgy of the Persian Gulf

(1992:Table 1).In contrast to Hauptmann's depiction, Figure 2.12(b) suggests that copper production in the Umm al-Nar and early Islamic periods, and the latetwentieth century were different by orders of magnitude, and that Umm al-Nar Period copper production was probably of a scale much more comparable to the twelfth-nineteenth century CE workings in the region than to the industrial production of the early Islamic and modern periods. This realization is critical in considering the organization of copper production in prehistoric southeastern Arabia, as discussed below. Likewise, the continuation of copper production throughout the second millennium BCE suggested by Hauptmann's diagram is not currently supported by any more archaeological evidence than is available for the Late Pre-Islamic Period (see above), which is presented as a period of zero copper production.

In attempting to explain these variations in production, the first question that arises is whether the pattern is the result of incomplete or unrepresentative archaeological research. The position taken in the following discussion is that, given the extent and duration of archaeometallurgical fieldwork in Oman, it is likely that the observed variations in copper production are a relatively accurate reflection of real phenomena, and require archaeological explanation. The major caveat that must be considered when evaluating this assumption is the lack of detailed archaeological research on Masirah Island. Given the lone radiocarbon date of ca. 1800 BCE that has come from a copper mine on the island (see above), this locality might contain evidence critical for our understanding of Wadi Suq Period and Late Bronze Age metallurgy. As noted above, there is also an element of uncertainty regarding the absolute date of the "Bronze Age" smelting remains recorded by the German Mining Museum, and a continuation of copper production into the Wadi Suq Period is possible. To begin, there are a number of factors that likely affected production levels at all periods in the history of copper extraction in southeastern Arabia. The first of these is the environmental cost of large-scale copper smelting, especially in terms of the amount of wood and wood-charcoal required for generating the high temperatures and reducing atmospheres necessary for smelting. A calculation of the wood requirements for the roasting and smelting of 600,000 tonnes of slag in the early Islamic Period, for example, suggests that perhaps 25 million acacia trees were harvested over a period of approximately 100 years to produce the required amounts of charcoal (cf. Weisgerber 1980a:75-76; l98Oc:ll9; Hauptman 198S:ll4). It is thought that such activities may have exhausted wood supplies, at least within the region of the mines themselves, and led to severe deforestation and desertification (Weisgerber 1991b:86). These figures, when applied to the 10-20,000 tonnes of slag produced in the Umm al-Nar Period (see above), suggest that perhaps a million trees were harvested for copper smelting in the second half of the third millennium BCE. Likewise, the minimum 80,000 tonnes of recorded Iron Age slag might have required the harvesting of several million trees. Although the amount of fuel required in the prehistoric

period is much lower than for the complex Islamic roasting and smelting operations, the reduced output of the Wadi Suq Period also correlates with increasing aridity in the region (e.g. Brunswig 1989; Carter 1997), which may have exacerbated the effects of large-scale fuel gathering. Thus, the enormous fuel requirements of Bronze Age and Iron Age smelting operations may have ultimately limited output, and may partially explain the observed periodicity in Omani copper production. The second factor to be considered for all prehistoric periods in southeastern Arabia is the prevalence of copper procurement through grave robbing. For example, although the evidence for primary copper production diminishes in the early second millennium BCE, a great number of copper-base objects are known from Wadi Suq and Late Bronze age funerary contexts, and secondary copper refining and casting are known from Tell Abraq (Weeks 1997) and the Shimal settlement (Vogt and Franke-Vogt 1987). Likewise, there is a significant number of copper-base objects, and copperworking areas, known from settlements and graves of the later first millennium BCE and early centuries CE (e.g. Ploquin and Orzechowski 1994; Haerinck 1994), yet this is a period for which no evidence of primary production has been recorded. It is likely that in these periods, the recycling of copper objects through tomb robbing was an important practice. Objects deposited in graves represented a source of metal that required simpler technology and fewer resources to exploit, and whose distribution was significantly wider than that of the copper ores themselves. Indeed, recycling must be regarded as an economically-viable alternative to primary copper smelting for any period of Oman's metalusing past, particularly from the late third millennium BCE onwards. It is likely, however, that tomb-robbing could have supplied only local needs, not foreign demand, especially given the practice of depositing copper-base objects in burials which continued into the early first millennium CE. In contrast to these factors which may have operated at all periods of local copper production, it is also apparent that some of the variations in output broadly coincide with economic and social changes in wider western Asia: Umm al-Nar Period production with the florescence of the Gulf trade (e.g. Edens 1992); Wadi

Geology and Early Exploitation of Copper

35

Suq recession with its collapse (e.g. Crawford 1998); early Islamic Period "industrial" production with the boom period of the Indian Ocean trade (e.g. Whitehouse 1979). That is, it seems clear that copper production in southeastern Arabia also responded to historically contingent events and processes. In the following discussion, the socio-economic and technological factors which interacted to affect copper production in southeastern Arabia are discussed.

Origins and Growth of Production in the Third Millennium BCE As described later in this chapter, the first copper-base objects appear in southeastern Arabia in the late fourth to early third millennium BCE, in both settlement and funerary contexts. Given the long history of metal use in the neighboring regions of Baluchistan, Iran and Mesopotamia prior to the third millennium, the origins of metallurgy in southeastern Arabia have usually been seen as external rather than indigenous. The origin of the southeastern Arabian copper extraction technology in southeastern Iran or Baluchistan is regarded by some scholars as particularly likely, even "obvious" (Cleuziou and M i r y 2002:304). These areas have a long history of primary metal extraction, and demonstrable technological parallels with the Oman Peninsula in other crafts, such as ceramic production. In fact, the stylistic and technological aspects of early pottery production in southeastern Arabia bear such close resemblance to contemporary industries across the Straits of Hormuz that a movement of people between the regions has been hypothesized (Miry 1996: 168-1 69). However, while the evidence for the origin of early Omani pottery technology in Iran/Baluchistan is compelling, the lack of information on the earliest copper production in southeastern Arabia means that hypotheses regarding the origins of smelting technology remain conjectural. The little evidence that does exist in Oman suggests a low level of technological understanding characterizable as a "trial and error" phase of production (Hauptmann 1985:92), which is inconsistent with the direct adoption of a developed extraction technology. Difficulties in assessing such hypotheses are further exacerbated by our limited understanding of earlier and contemporary metal

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Early Metallurgy of the Persian Gulf

smelting in the putative "origin" zone, at sites such as Tepe Ghabristan, Tal-i Iblis and Shahdad on the Iranian Plateau (Pigott 1999a). Well-studied extraction procedures, such as those known from Bronze Age site of Tepe Hissar, for example (Pigott et al. 1982; Pigott 1989), cannot be paralleled in Oman. The evidence might therefore best be considered as an example of "stimulus diffusion": the idea of metal use may have originated elsewhere, for example with the people who brought pottery technology to southeastern Arabia, but the smelting technology itself did not, and was developed locally. A Mesopotamian connection to early Omani copper extraction was hypothesized in a number of early archaeological studies, based upon the discovery of Jemdet Nasr pottery vessels and beads in local Hafit graves alongside the earliest copper-base objects (e.g. During Caspers 1971:43; Frifelt 1980:278). However, Mesopotamia was a center of metalworking and the production of finished objects rather than of mining and smelting, and the presence of Mesopotamian prospectors in Oman (e.g. Orchard 1995:155; Frifelt 1980) seems a priori to be unlikely. Mesopotamian influence on early copper production in southeastern Arabia is much more likely to have been in the economic sphere rather than the technological. For example, the expansion in scale and geographic scope of the Gulf trade from the third millennium has been related to an increasing Mesopotamian demand for metals, woods, and luxury goods that, with the collapse of the Uruk expansion, could no longer be obtained from lands to the north of Mesopotamia (e.g. Crawford 1998:34; Cleuziou and Tosi 1989:30; Potts 1990a:92). Some scholars regard the scale of Omani copper production as reflecting this Mesopotamian demand quite directly. C. Edens (1992:130-132), for example, hypothesizes a dramatic increase in the demand for copper in the Old Akkadian Period, as copper moved from a luxury good to a necessity in Mesopotamian society. Copper production in southeastern Arabia is thought to have escalated in response to this changing demand, partly as a result of the fact that participation in the Gulf trade had become "deeply embedded" in local southeastern Arabian communities (Edens 1992:118).

The theorized increase in Mesopotamian demand and Omani copper production is contemporary with a significant expansion in the number and size of southeastern Arabian settlements, and the three developments have therefore been regarded as causally linked (e.g. Berthoud and Cleuziou l983:243-245; Cleuziou 2002: 199-200). Costa and Wilkinson (1987:232), for example, suggest that copper production was "the prime stimulus" behind the expansion of settlement in the Umm al-Nar Period, and it is not hard to find parallels with models relating external demand to intensification of settlement in other copper-producing regions of Bronze Age western Asia (e.g. Knapp 1986:12). Omani participation in the longdistance exchange network linking Mesopotamia and Meluhha, grounded upon copper production, also introduced a great variety of foreign goods of prestige nature into the region. As discussed fully in Chapter Eight, the exchange of these goods probably played a significant role in the economic integration of southeastern Arabia. The significance of this newly-emerged integration for copper production is discussed below. General studies of the cuneiform sources discussed above also suggest that Magan's role in the Gulf trade peaked in the later third millennium BCE, contemporary with the increased Mesopotamian demand for copper hypothesized by Edens. Unfortunately, although Umm alNar Period copper production refuse can be clearly differentiated from that of the Iron Age or the early Islamic Period, there have been no systematic studies of variation in the scale and technology of copper extraction within the more than half a millennium span of the Umm al-Nar Period itself. While the evidence from the site of Maysar 1 suggests a date in the last few centuries of the third millennium BCE, the date of other "Bronze Age" smelting sites is far from certain. Thus, it is impossible from archaeological evidence to support or deny hypotheses like increased Omani copper production in the Akkadian Period, much less causally link this increased production to category shifts in Mesopotamian demand for raw materials and the expansion of Omani settlement. Regardless of the limitations of the available archaeological evidence, there can be little doubt that external factors such as those outlined above played a role in the development and scale of Umm al-Nar Period copper production in southeastern Arabia.

Having considered southeastern Iran and Baluchistan in terms of the origins of Omani metallurgy, and Mesopotamia in terms of increasing foreign demand for the raw material, one could also consider the role of other trading partners of Magan, notably Dilmun and Meluhha, as important consumers of southeastern Arabian copper. The evidence for copper use in both these areas is significant, although reliable analytical links to the use of Omani copper are scarce. The case for the use of Omani copper in Dilmun seems simplest, as Dilmun's role as middleman in the Bronze Age copper trade through the Gulf is well established). Nevertheless, the limited evidence that exists comes only from the terminal third and early second millennia BCE (Prange et al. 1999; Weeks forthcoming a), and while strongly indicative of the use of Omani copper, may also support the use of metal from other sources. The case for the use of Omani copper in the Indus region is less certain: the presence of planoconvex ingots at Lothal has been regarded as evidence for the use of southeastern Arabian copper, as has the trace element composition of objects from the site and elsewhere in the southern Harappan orbit (Rao 1979:233; 1985524-527). Needless to say, these arguments are of limited strength, as planoconvex ingots occur widely across western Asia and are unlikely to have been an exclusive product of southeastern Arabia (Chakrabarti l998:3 11; Weisgerber and Yule 2003:48), and trace elements can only rarely provide a conclusive guide to metal provenance. Nevertheless, hypotheses suggesting the use of Omani copper in the Indus are plausible, given the archaeological evidence for exchange between the two regions (Weisgerber 1984; Potts 1993c; Edens 1993), and the likelihood that a region as large as the Indus must have been utilizing copper from multiple sources (Kenoyer and Miller 1999: 117-1 18). Certainly, such theories deserve to be assessed on their archaeological merit, rather than dismissed as reflecting supposed political biases or the desire to explain South Asian civilization as non-indigenous (cf. Chakrabarti and Lahiri 1996:199). Having discussed the external factors affecting copper production in Bronze Age southeastern Arabia, it is clear that the internal factors, including the demand for copper from a growing Omani population increasingly

Geology and Early Exploitation of Copper

37

reliant on metals, must also have influenced production. The scale of local consumption is reflected in the large number of copper-base objects deposited in the Umm al-Nar Period collective graves found across the peninsula (e.g. Benton 1996; Potts 2000). These funerary practices must have been supported by levels of copper production much higher than seen in the early third millennium, where comparatively few copper-base objects are known from funerary contexts (see below). A corresponding increase in metal use in Umm al-Nar Period settlements is also seen, with sites such as Umm an-Nar Island (Frifelt 1995), Tell Abraq (Weeks 1997), Bat (Frifelt 1979:584), Ra's alJinz RJ-2 (Cleuziou and Tosi 200057-59), and Ghanadha 1 (A1 Tikriti 1985:15) containing relatively large numbers of copper-base objects. In examining the internal socio-economic factors affecting copper production in southeastern Arabia, the nature of local subsistence and exchange patterns is of particular significance. The third millennium is usually characterized as a period of increasing cultural integration in the Oman Peninsula, directly related to the expansion and consolidation of intra-regional trade networks linking the complementary subsistence regimes of coastal and inland settlements (Cleuziou and Tosi 2000:26; Cleuziou and Tosi 1989:17; Crawford 1998:120; Mkry 1997: 188; Charpentier 1996). There seems little doubt that copper produced in the mountainous interior would have been a significant component of this internal exchange system, along with agricultural and marine products, as attested by the distribution of metal at Bronze Age sites across the peninsula. For example, the abundance of copper objects in debris contexts from Ra's al-Jinz RJ-2 suggests that copper was far from a rare resource in this coastal area distant from inland primary production centers (Cleuziou and Tosi 2000:57-59), and this finding is supported by discoveries at other third millennium coastal sites listed in the preceding paragraph. The increasing economic integration of the region may thus have played a role in the expansion of local copper production. Although the power of long-distance exchange to act as an agent of economic growth has been emphasized by a number of scholars,

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Early Metallurgy of the Persian Gulf

Figure 2.1 3 A slag-filled planoconvex copper ingot from AI-Aqir in Oman (Hauptmann 1987: Abb. 2).

Cleuziou and Tosi (2000:71 n. 21) are no doubt correct in stating that local exchange networks were of much greater importance than foreign exchange to the economic welfare of the Bronze Age inhabitants of the Oman Peninsula. Parallels can be drawn with a thought-provoking analysis of Bronze Age metal extraction in Europe by S. Shennan (1999), that examined the production of copper in the eastern Alps in cost-benefit terms, based around Ricardo's "Law of Comparative Advantage" and the notion that early copper producers were rational economizers (1999:353). Shennan's study was itself based upon

earlier ethnographic studies of pre-modern production and inter-regional exchange systems in the Grassfields region of Cameroon, undertaken by M. Rowlands and J. Warnier (Shennan 1999:353). The model could be reduced to the idea that "it is not worth producing commodity X yourself if you're better off producing commodity y and obtaining commodity X in exchange for it, in other words, by specializing" (Shennan 1999:353). According to Ricardo's Law, specialization is ultimately rooted not only in the localized distribution of necessary raw materials, but in regional variability in the costs of production caused by ecological, technological and social determinants (Shennan 1999:354; see also Costin 2001:308). Ricardo's Law represents an explicitly formalist understanding of production and exchange systems, which some scholars may regard as unjustified. Nevertheless, the economic nature of the Gulf trade is made eminently clear by the surviving cuneiform evidence from Mesopotamia (see above). Although often funded by large Mesopotamian institutions, the copper trade was undertaken as a venture in which the economic success or otherwise of the individual merchant was calculable. Moreover, specific details of the trade, especially the attempts to distribute raw materials of questionable quality for which Ea-Nasir was so strongly criticized by his partners, clearly resemble aspects of modern entrepreneurial behavior. The presence of a number of planoconvex copper ingots from Bahla with deliberately-produced cores of slag (see Figure 2.13) tallies well with the cuneiform evidence for complaints about low quality copper traded by Ea-Nasir. It has been suggested that these ingots represented a votive deposit for a dam at AlAqir, and that their slag cores reflect the production of "cheaper" offerings to an unknown deity or deities (Weisgerber and Yule 2003:SO-51). However, such an interpretation is far from certain, and the ingots might also indicate that the Omani producers of the copper sought economic gain from their activities, to the point of deception. Overall, the "spirit of the gift" seems not to have influenced exchange relationships to a significant extent, and a formalist approach to Gulf copper production and trade seems justified.

Similarities are immediately apparent between the pre-modern Grasslands and Alpine Bronze Age economic systems described by Shennan, and the southeastern Arabian Bronze Age production and exchange network. For example, there is evidence for only a limited number of production centers for Omani black-on-red funerary pottery in the region in the third millennium, whose wares were distributed on a regional and sub-regional scale (M6ry 1996, 2000). Similarly, there is evidence for localization of shell ring production in the Ra's al-Jinz and Ra's al-Hadd regions (Charpentier 1994; Cleuziou and Tosi 2000:35), soft-stone vessel manufacture at Maysar 1 and elsewhere (Weisgerber 1981; David 1996). In each of these cases (pottery, shell rings, soft-stone vessels), the geographical distribution of raw materials would have allowed for production to take place at a great many more locations than it actually was. The fact the production loci are limited in number suggests that some form of regional specialization existed in third millennium southeastern Arabia, that might be understood as reflecting the operation of Ricardo's Law. The variability and complementarity of specialized subsistence and production activities within southeastern Arabia, and the regional exchange systems that developed in the Umm al-Nar Period, have been commented upon by numerous scholars. Most importantly for our study, Shennan (1999:362) noted that "one of the consequences of large scale regional exchange systems that operate on Ricardian principles ...is that they led to economic growth. That is to say, total regional production is higher than it would have been if individual communities had remained self-sufficient". Ricardo's Law is significant in providing an economic underpinning for the interdependence of specialization, exchange, and economic growth in so-called "commercial" models of the development of social complexity (e.g. Brumfiel and Earle 1987:l). Such growth in the Bronze Age exchange system of southeastern Arabia has been commented upon specifically by Cleuziou and Miry (2002:307, 310), who emphasize that exchange is "the main concept which rules any successful adaptation to an ecological milieu in Arabia".

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Thus, the significance of intra-peninsular exchange networks in the development of southeastern Arabian copper production should not be underestimated. When examining the apparent increase in social complexity in the region in the later third millennium, it is also useful to consider the nature of the exchange systems which develop under Ricardian principles: although all benefit from increased specialization and economic integration, not all benefit to the same degree (Shennan 1999:354). The inequalities inherent in the developing regional exchange system, and the competition between local and kinship groups that this fostered, may have played a significant role in the development of social complexity in southeastern Arabia in the Umm al-Nar Period, as discussed more fully below.

Possible Reduction in Copper Production in the Second Millennium BCE There is a dramatic reduction in the amount of evidence for copper production in southeastern Arabia in the early second millennium BCE. As discussed above, it is difficult to know if this lack of evidence reflects an actual reduction in production in the Wadi Suq Period, or if it is merely a product of a biased archaeological record or uncertainty in the interpretation of the evidence. A number of scholars have argued, based upon circumstantial evidence, that copper production in the Wadi Suq period continued at levels similar to those seen in the third millennium. However, there is little in the way of conclusive evidence to support either position, and it is worth considering some of the factors that may have contributed to a decline in Wadi Suq Period copper production, as hypothesized by Weisgerber (1981) and Hauptmann (1985). In particular, the apparent reduction in copper extraction is contemporary with a decline in the number, size, and complexity of settlements in southeastern Arabia (Cleuziou 1981; Carter 1997; Magee 1999:51). This change was initially regarded as a transition to an archaeological "dark age", resulting from the domestication of the camel and a consequent move to full-time camel nomadism (Cleuziou l 9 8 1).However, recent evidence for the continued presence of sedentary communities throughout the second millennium has made it clear

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that this period represents an evolution in the prehistory of southeastern Arabia society (Potts 1997b:52), rather than a revolution as initially characterized. Nevertheless, while a transition to full-time nomadism is no longer supported by the evidence (e.g. Carter 1997; Potts 1997b:52), an explanation of the development of the Wadi Suq Period that incorporates at least some movement away from sedentary life remains plausible (contra Carter 1997:96). The transition from a third millennium cultural milieu in which nomadic elements and seasonal sites played a significant role (e.g. Cleuziou and Tosi 1989, 2000; Crawford 1998:140), to one in which nomadism played a greater or dominant role is not difficult to imagine. This view is compatible with the archaeological evidence, which indicates that very few large sites are occupied in the second millennium BCE, that these few sites are all located in the northern coastal region (Carter 1997:Figure 2), and that they witness a strong (though not complete) re-orientation of their economy away from agricultural production to the exploitation of marine resources (Carter 1997:94; Potts 1997b352). Significantly, an hypothesized move towards nomadism cannot be used a priori t o explain a reduction in the amount of copper produced in southeastern Arabia. The ability of nomadic groups to mine and smelt large quantities of copper has been demonstrated in other Bronze Age archaeological contexts, most notably on the Eurasian Steppe a t the site of Kargaly (Chernykh 2002). Such evidence counters Carter's (2001:196) claims that there was a lack of permanent sedentary settlement in the copper-producing regions of inland Oman "such as would underpin an export trade in copper of the scale indicated by the Mesopotamian texts". A better explanation of the situation perhaps lies in the decay of the integrated system of exploitation of agricultural, marine and mineral resources that characterized the third millennium BCE. As discussed earlier in this chapter, the economic integration and regional specialization of production within southeastern Arabia at that time no doubt led to a growth in the scale of the local economy. In contrast, there is evidence to suggest that the Wadi Suq Period witnessed an economic disintegration characterized by significantly reduced regional interaction

(e.g. Magee 1999:51). In particular, the limited importance of agricultural settlements in the interior oases (Carter 1997) was almost certainly of great significance, representing the disappearance of one of the major nodal categories of the Bronze Age regional exchange system. The consequent reduction in economic integration is indicated archaeologically by the proliferation of raw-material sources exploited for pottery and stone vessel manufacture in the second millennium, and the lower quality of the vessels produced, which suggests the existence of non-specialized production at multiple locations (David l996:3 8-39; MCry 2000), in addition to "new patterns of distribution and consumption" (Cleuziou and M i r y 2002:302). Reduced intra-regional integration, if operating within the economic model discussed by Shennan (1999), may have led to lower levels of copper production. Of course, it is also possible to relate the reduced Wadi Suq Period copper production to broadly contemporary external economic factors. These include, in particular, the reduction in the foreign demand for Omani copper caused by political upheavals in Mesopotamia, the availability of Anatolian and Cypriot copper in Babylonia by ca. 1750 BCE, and the end of the Mature Harappan Period in the Indus region at ca. 1900 BCE. The general importance of the Gulf trade for the Mesopotamian political economy is indicated by a number of Mesopotamian cuneiform inscriptions in which the rise to power of a leader is accompanied by claims alluding to his newly-restored control of trade through the Gulf. Examples include Ur-Nanshe's claims of wood brought from Dilmun (Potts 1990a:88), Sargon's boast of boats from Dilmun, Magan and Meluhha docking at the quay of Agade, and the "restoration" of the Magan trade into Nanna's hands achieved by Ur-Nammu (Potts 1990a:144). It is interesting that these declarations generally come from the formative periods of new political entities in southern Mesopotamia, indicating that political instability in southern Mesopotamia could have seriously deleterious effects on the Gulf trade (e.g. Crawford 1996). Thus, the political and economic changes in southern Mesopotamia in the Old Babylonian Period (Crawford 1996) almost certainly had a serious effect on the demand for southeastern Arabian copper.

Looking to the east, the status of the Indus region as a consumer of Omani copper is still disputed (e.g. Weisgerber 1984; Rao l985:.S24; Cleuziou and Tosi 1989:42; Chakrabarti and Lahiri 1996:199). As has been discussed above, the use of Omani copper in the Indus region remains a very plausible hypothesis due to the geographical proximity of the two regions, the archaeologica evidence for close exchange contacts between them, and the likelihood that an area as large and densely occupied as the Indus was utilizing copper from a multiplicity of sources. Any reliable proof of this hypothesis, however, will depend upon further programs of archaeometallurgical research. Even if copper was not exchanged between the two regions, the demise of the Harappan civilization may nevertheless have been important for copper production in southeastern Arabia, as a factor in the general decline in scale and geographic scope of the Gulf trade in the early second millennium BCE. Significantly, however, the cultural and economic developments in the various regions discussed above are not perfectly synchronized. The Wadi Suq Period in southeastern Arabia, and the dramatic changes in settlement size, frequency, location, and subsistence that characterize it, is generally regarded as beginning between 2000-1900 BCE. This is broadly CO-incidentwith the disappearance of Magan from Mesopotamian cuneiform sources, and the end of the Indus civilization. However, cuneiform evidence indicates that the first quarter of the second millennium BCE witnessed a flourishing copper trade between Dilmun and Mesopotamia. Thus, if the meager evidence for primary copper production in the Wadi Suq Period is regarded as an accurate reflection of the situation, it is possible that "Dilmun" copper was coming from a region other than southeastern Arabia by this time, a possibility already suggested by R. Carter (2001:196). As discussed in Chapter Seven, there is evidence from archaeological lead isotope analyses which may tentatively support the idea that some metal from non-Omani sources was reaching Dilmun (Weeks, forthcoming a). However, one other factor to consider, as noted above, is the imprecise chronology for copper extraction in the Oman Peninsula. "Bronze Age" smelting sites recorded by the German Mining Museum Project, usually dated to the Umm al-Nar Period, could feasibly represent the remains of copper production into

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the Wadi Suq Period. Regardless, it is clear that explanations for the changes in copper production in southeastern Arabia in the early second millennium BCE must allow for complex interactions between local and regional economic systems, environmental considerations, and the ways in which copper production was articulated with broader subsistence practices. Expansion and Contraction of Iron Age Copper Production Copper production in southeastern Arabia again attains significant levels in the local Iron Age. The increase in the quantity of smelting debris dating to the late second or early first millennia BCE can be correlated with the dramatic expansion of settlement in piedmont areas of southeastern Arabia, probably related to the introduction of falai irrigation technology in the local Iron I1 period (Magee 1999). Internal factors seem to have played a major role in the development of copper production at this time, most notably the increase in demand generated by a greatly expanded population. This hypothesis is supported by numerous examples of large-scale local consumption of copper-base objects (Weisgerber l 9 8 8). These include unrobbed Iron Age tombs such as the collective horseshoe-shaped grave from Qidfa in Fujairah which contained hundreds of leaf-shaped arrowheads, dozens of vessels, large braceletslbangles, axes, and more than 10 hilted copper daggers (Corboud et al. 1988), the purported tomb robber's hoard from IbriISelme with more than 300 copper-base objects including vessels, braceletslbangles, and hilted daggers (Yule and Weisgerber 2001), and the graves and settlement occupation at A1 Qusais in Dubai which produced more than 800 copper-base arrowheads (Potts 199Oa:359-361). Interestingly, the increase in copper production in the Iron Age is contemporary with an increase in regional economic integration, very similar in nature to that seen in the Umm al-Nar Period. Although the absolute scale of settlement and population in Oman in the Iron Age was greater than in the third millennium, a similar polycentric distribution of power is hypothesized (Magee 199954-55), based upon the control of regionally diverse and complementary resources. Magee and Carter (1999:176) have proposed a model in which coastal, desert, and inland settlements formed a

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"regionally-specialized economy" that, following the model discussed above, is likely to have generated an increase in local copper production. P. Magee (personal communication) sees greater local demand for copper as related particularly to increasing conflict between Iron Age polities (and the consequent need for weaponry), and the role of copper implements in status display by newly-emergent elites. There is some evidence that Iron Age copperworking was practiced by "attached specialists", if the concentration of copperworking activities within the unusual columned building at Muweilah is any guide (Davis 1998). The role of attached specialists in the generation and maintenance of social hierarchies has been widely discussed (e.g. Earle 1994:426 ff.), and indeed a similar situation in the Umm al-Nar Period might be indicated by the location of copperworking facilities directly adjacent to the main tower at Hili-8 (Cleuziou 1989). The dearth of archaeometallurgical research on Iron Age copper smelting means that is virtually impossible to address the technological developments which may have underlain this increase in copper production in southeastern Arabia. It seems that the Iron Age saw the first large-scale exploitation of the massive sulfide copper deposits (Weisgerber 198 8 :286 ) , incorporating the smelting of both oxide ores from the gossan and unaltered sulfide ores. The massive sulfide deposits at sites like Lasail, Bayda and 'Arja are the largest copper ore-bodies in southeastern Arabia, and the ability to exploit them would no doubt have allowed a significant increase in copper production in the region. However, certain technological advances would have been required to effectively utilize the sulfidic ores, and intensive mining would have been necessary to exploit the low-grade oxide mineralization of the gossans. The lack of detailed archaeological evidence for these mining and smelting technologies precludes the formation of a sound hypothesis regarding their effect on Iron Age copper extraction. Assessing the impact of foreign demand for Omani copper in the Iron Age is also difficult. There is a complete lack of textual evidence regarding southeastern Arabia in the early first millennium BCE, and it is not until the reign of Assurbanipal in 640 BCE that Neo-Assyrian cuneiform sources mention a ruler of the

region, Pade king of Qade, who brought unspecified (but rich) tribute to Assyria (Potts 1990a:393). Later documents related to the Achaemenid administration of southeastern Arabia (Potts 1990a:394-400) do not mention the export of goods at all. It has been suggested that Neo-Assyrian and Neo-Babylonian references to obtaining bronze from Dilmun, sometimes in quantities of hundreds of kilograms, reflects the use of metal originally from southeastern Arabia (Potts l99Oa:NO). This hypothesis remains uncertain, but is certainly supported by the evidence for Iron Age copper extraction in Oman. One need only examine the meager historical evidence for copper export from Oman in the early Islamic Period to understand that large-scale copper production and trade can be seriously under-represented in historical sources. Thus, external markets for the copper produced in Iron Age southeastern Arabia may have been important. In this context, it is interesting to note the suggestion of Magee and Carter (1999:175) that developments in the early Iron Age in southeastern Arabia might be related to a "revitalized exchange relationship with Iran". This contact with the north is indicated by a wide range of material goods recovered in southeastern Arabian contexts, particularly ceramics (e.g. Magee 2002:Figure 2). Likewise, there is abundant archaeological evidence attesting to contact between southeastern Arabia and the central Gulf in the Iron Age (e.g. Potts 1990a:325-326), and Dilmun may have been an important foreign consumer of Omani copper. The factors underlying the apparent reduction in copper smelting in the later stages of the Omani Iron Age remain obscure. This is chiefly because there has been so little analytical work on Iron Age smelting sites in Oman, and the chronology and development of copper extraction within the Iron Age are consequently unknown. The only secure dates for Iron Age smelting relate to the very large-scale extraction in the Raki area, which is radiocarbon dated to ca. 1100-800 BCE (see above) and thus must be placed early in the local Iron Age sequence. Evidence from other elements of the archaeological record indicates a significant contraction of Omani settlement beginning in the Iron I11 Period, i.e. after about 600 BCE. Explanations proposed for the reduction in settlement

largely revolve around access to water, and have included the lowering of local water tables and the silting up of the falaj irrigation systems that were critical for agricultural production in the preceding Iron I1 Period (Magee 1999). As the florescence of Iron Age copper production seems to be related predominantly to an increase in the internal demand from a rapidly expanding Iron I1 population, lowered production from the mid-first millennium BCE might likewise be due to the reduction in local settlement and population. The possible continued importance of Bahrain as a consumer of Omani copper in the sixth to fourth centuries BCE is indicated by the extent of metalworking operations at Qala'at al-Bahrain City IVc-d (Harjlund and Andersen 1997:165-1 74). The continued use of copper for tools and weapons in the central Gulf in the first millennium BCE is stressed by Harjlund and Andersen (1997:210). Thus, external demand for copper does not seem to have disappeared, but internal variations in demand for copper remain the most likely cause of falling production.

Organization of Early Copper Production As outlined above, archaeological evidence and Mesopotamian historical sources indicate that copper production was a major productive activity in Bronze Age southeastern Arabia, and that copper from Magan was the most prominent material exchanged in the Gulf and Indian Ocean trade network. It is of interest to know both how Bronze Age metal mining and smelting were organized to meet the large internal and external demand for copper, and how the production of this copper affected other areas of southeastern Arabian economy and society. Natural limitations on the distribution of raw materials and the complexity of extraction technology have suggested to scholars that early metallurgy required inherent specialization (e.g. Childe 1937:9; Kristiansen 1987:33; White and Pigott 1996:151; Ottaway 2001:95). Moreover, examination of the archaeological record from Bronze Age southeastern Arabia indicates that primary copper extraction was undertaken at a limited number of sites, and thus must have been a specialized activity. Archaeological discussions of the economic and

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socio-political consequences of specialized metal production on ancient societies can be traced back to the writings of V. Gordon Childe and his contemporaries. However, as noted by Clark (1995) and Wailes (1996b:5), much early archaeological research on specialized production proceeded without an explicit understanding of what was in fact meant by the term "specialization". One result of this lack of definitional clarity was that anachronistic analogies based upon modern craft specialists and specialization were commonly employed (e.g. Clark 1995; Budd and Taylor 1994), with mining, smelting and smithing in particular regarded by Childe (1937:40, 134-136) as demanding full-time specialization. Such biases limited the ability of scholars such as Childe to accurately characterize and comprehend the great variability of early specialized production systems, and to assess their interaction with other social, political, and economic factors. These oversights have been remedied in the modern literature on the topic, where explicit (if sometimes competing) definitions of specialization can be found (esp. Costin 2001, 1991; Clark 1995; Clark and Parry 1990). Specialization can be defined in the simplest terms as the degree to which there are fewer producers than consumers of a particular object or material (Costin 2001:276), with the caveat that consumers are nondependents of the producer. Correspondingly, as distribution is a necessary complement to specialization, it is clear that specialized production was as widespread in prehistory as exchange, and must have existed in one form or another in most societies (Clark 1995:279). Archaeological studies of specialization are abundant, and have focused predominantly on identifying different types of specialized production in past societies, and determining the relationship between craft specialization and social complexity (e.g. Costin 1991; Clark and Parry 1990; Stein and Blackman 1993; Cross 1993; Wailes 1996a; Brumfiel and Earle 1987; Peacock 1982; Van Der Leeuw 1977). The material correlates of particular specialized production regimes have received particular attention. This is because definitions of specialization in non-Capitalist contexts have most commonly been extracted from historical sources or ethnographic studies, in which the type or degree of specialization is recognized by such

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characteristics as the amount of time spent in a particular activity, the proportion of subsistence needs obtained from the activity, payments in goods or money received for production, and the existence of a name for the specialist activity (Costin 1991:3). These characteristics have few or no readily identifiable material correlates, and the reconstruction of production systems in non-literate ancient societies would be an impossible undertaking if such variables were all that was available for investigation. However, it is obvious that ancient production processes do leave behind material remains, and Costin (1991:l) has suggested that production should be more readily reconstructable from archaeological evidence than a number of other economic processes (such as exchange) that have received a great deal of archaeological attention. The material remains of production processes (e.g. tools, raw materials, waste products, finished objects), and their differential spatial distributions, have significant potential to act as indices of both the type and extent of specialization. They can provide a window into specific craft production systems. From the preceding paragraph, it can be seen that accurate reconstructions of ancient production systems are dependent upon two main factors. These relate to our ability to: 1. Identify the material remains of specific production technologies (i.e. tools, raw materials, waste, finished products). 2. Recognize the material correlates of specialized production, which might include variations in the spatial distribution of production loci, as well as evidence for the standardization, skill and efficiency of manufacturing techniques. Understanding of the first component derives largely from detailed technical studies of archaeological materials, informed by laboratory analyses, modern experimental reconstructions of ancient technologies, and by ethnographic and historical accounts of non-industrial production technologies. The second component is perhaps more complex and frequently less certain in its outcomes, requiring the development of ethnographically, historically, or otherwise empirically-informed theories (i.e. middle-range theories) relating artifact attributes and the differential spatial distribution of production indices to specific forms of specialized production.

One of the most frequently cited methodologies for investigating specialization and production in the archaeological record is that developed by Costin (1991). As noted by Clark (1995:288), this is partly because Costin's discussion of the issue, like the important work of Evans (1978) before it, focuses very closely upon the identification of the archaeological correlates of production behavior. To use Costin's (1991:43) own words, her definition of specialization "is relatively straightforward to operationalize archaeologically", and focuses upon the four production variables of context, concentration, scale, and intensity (Costin 1991:8-18, Figure 1.4). Context reflects the degree of elite sponsorship of production, varying from attached to independent production. Concentration represents the spatial distribution of production loci, varying from dispersed to nucleated. Scale is a measure of the size and constitution of individual production units or groups, varying from small and usually kin-based units to larger groups of unrelated individuals. Intensity represents the amount of time spent doing the specialized task in comparison to other activities, varying from part-time to full-time. Based on the most common associations of these four variables, Costin constructs a typology incorporating eight production types, e.g. "community specialization" and "nucleated workshops", which can be compared to those found in earlier typologies of craft production, including Peacock (1982) and Van Der Leeuw (1977). The clearest conclusion to be drawn from the archaeological literature on craft production is that "specialized" copper production in southeastern Arabia could have taken a number of different forms: from small scale, independent, part-time or seasonal production by semi-specialists to full-time production with very high output by specialists attached to large political institutions. Given the emphasis that has been placed upon certain types of craft specialization in the development of political complexity (e.g. Wailes 1996a; Clark and Parrty 1990; Brumfiel and Earle 1987), the implications of these different production types for our understanding of Bronze Age southeastern Arabia are clear. Utilizing the categories discussed by Costin (1991) allows us to move beyond the a priori and un-enlightening understanding of metallurgy as a specialized

discipline, to examine in detail the economic, technological and socio-political factors that contoured copper production in Bronze Age southeastern Arabia. The evidence for the mode(s) of copper production prevalent in Bronze Age southeastern Arabia is addressed below. Primary Copper Production in Bronze Age Southeastern Arabia The manufacture of any copper object incorporates a number of discrete stages of production, from mining, ore preparation, smelting, and refining, to object fabrication processes such as casting and hammering. Significantly, there is clear potential for a geographical separation of these productive activities: it is not only theoretically possible for these processes to have taken place in widely separated locations, it is clear from the archaeological record of Bronze Age southeastern Arabia that primary extraction was generally undertaken near to copper ore sources, while newly-won (and probably recycled) copper was utilized for object fabrication at habitation sites distant from the loci of primary copper extraction. Such a wide geographical focus (Omani copper was used as far away as Mesopotamia and perhaps the Indus Valley) introduces many difficulties in the interpretation of production. In the following discussion, therefore, the focus is upon the organization of primary copper extraction only, i.e. mining, smelting, and the production of ingots. Copper in ingot form is a widelyexchanged category of material that moved both within and beyond the boundaries of Bronze Age southeastern Arabian society. Newly-won raw copper and semiprocessed copper ingots form a class of goods whose production and trade can be studied, in many respects, separately from the productive processes associated with object fabrication in southeastern Arabian settlement sites and across western Asia. Even a study of production limited to primary copper extraction is not without complications. Each of the main activities of mining, ore processing, and smelting has unique requirements in terms of technological and ritual knowledge, tools, raw materials, physical strength, etc., and each may have had distinctly constructed ideologies delineating the status of the activity, rights of participation, access to requisite knowledge (Ottaway 2001). Thus, there is no reason to assume that mining,

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ore processing, and smelting were organized along similar lines, or that production groups for each of these activities were constituted in the same way (i.e. of the same or similarly related individuals). In the case of southeastern Arabia, evidence for early copper extraction of the standard required to adequately reconstruct production systems is meager. For example, the archaeological evidence available for Bronze Age mining is almost non-existent. Where estimations of the scale of orelgangue extraction are available, as at Maysar 2 (10,000 cubic meters of rock mined using open-cast methods), no data regarding the duration of exploitation, or the scale of production (i.e. size of production units) is available. Archaeological evidence of ore processing activities is available from many sites, but again the lack of chronological and spatial control at most Bronze Age sites severely limits attempts at explanation. Furthermore, the archaeological evidence for houses, storage areas, and other habitation remains at copper extraction sites, which is crucial for assessing the possible scale and intensity of production, is extremely limited. Such information is available only from sites where primary extraction was undertaken in sedentary habitation contexts, as at Maysar 1 and Wadi Fizh 1, and only Maysar 1 has been the subject of archaeological excavation (Weisgerber 1980b, l 9 8 1; Hauptmann 1985). As a result, reconstructions of copper production in the region have utilized estimates of total output as a proxy for the organization of extractive industries. Hauptmann's estimates of total copper production in Bronze Age southeastern Arabia are of the order of a few thousand tonnes (see above), a value that indeed seems very large when considered in terms of the number of individual smelting operations that it might represent. For example, if one smelting furnace produced approximately five kg of copper per operation (see above), then Bronze Age production in southeastern Arabia represents hundreds of thousands of smelting operations. These raw numbers suggest the possibility of highly specialized, large-scale, intensive and closely controlled copper production in the region. Based upon such considerations, Hauptmann (1985: 114) regards copper production at some sites in Bronze Age Oman as having taken place "on an industrial scale".

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However, the absolute level of output is not used by Costin (1991) in her analyses of specialized production, and she has outlined the weakness of such an approach (Costin 2001:291): "The use of 'output' as an indicator of the organization of production warrants greater caution, particularly in the absence of detailed knowledge of technology, intensity, and an approximation of the number of sources or work groups and the time over which an assemblage was produced and used ...There is, at best, only a weak correlation between the quantity of an artifact recovered, the output (or scale of production) of the individual production units making those objects, and the way production was organized." Archaeological and ethnographic research has repeatedly demonstrated that very high levels of output can be achieved by groups operating under relatively simple production regimes (White and Pigott 1996:169; Shennan 1998:200-201). Thus, when the limitations of the archaeological evidence from southeastern Arabia regarding chronology, scale, and intensity are considered, industrial organization becomes only one possible explanation for high total output, and is certainly no more plausible than less intense production undertaken over many generations or centuries. Given the chronological limitations of the evidence from Oman, largescale extraction (as seen in the open-cast mining operations at Maysar 2) cannot be linked with intensive exploitation of the resource. Furthermore, the copper deposits most frequently exploited in Bronze Age Oman are relatively small, numerous, and found across a large area, a factor that limited the ability to intensify mining activities at individual large ore deposits. On a smaller scale, estimates of total output at Maysar 1 (Weisgerber 1980b, 1981; Hauptmann 1985) in the Wadi Samad, Oman, have also been used as a proxy for the way in which production was organized. The relatively small amount of primary smelting slag found at Maysar 1 (approximately 100 tonnes) is regarded as evidence that copper production was a "part-time activity, one that for most residents was secondary to agricultural and pastoral pursuits" (Edens and Kohl 1993:26). It is doubtful whether it is correct (or even useful) to classify copper production at Maysar 1 as "secondary" to agricultural production based upon

total output: a term such as complementary is perhaps more appropriate. Nevertheless, the location of metal extraction facilities within an agricultural village does indeed suggest that metal production was integrated with subsistence production, with resultant implication for the intensity of production. It seems likely that production in such a context was seasonal, if not in terms of the total cessation of production, at least in terms of changes in productive intensity. This is not a surprising conclusion, for as noted by Costin (2001:280), the evidence from ethnographic studies overwhelmingly indicates that "for most nonindustrial artisans production intensity varies throughout the year". Seasonal production of copper in southeastern Arabia is also thought to have been indicated by other evidence, notably the location of sites in relation to natural resources: "It is interesting that the third millennium copper smelting sites found in 1975 were all located near water and arable land ...These settlements are not situated on top of the ore deposits as became true later on. The difference between the third millennium smelting village in its fertile surroundings compared with later Islamic smelting villages in places where cultivation would be very difficult, suggests that in early times copper production was an integrated part of community life while later on it became a specialized industry, possibly for export at the behest of foreign authorities" (Hastings et al. 1975:12). It is clear that characteristics other than "overall output" must be studied in order to adequately understand the organization of copper production, and the investigation of the evidence from individual sites is an obvious starting point. Examination of the distribution of metal production refuse at Maysar 1 and other sites in the Wadi Samad facilitates an investigation of the context, concentration, scale and intensity of productive activities. At Maysar 1, pyrotechnological processes were distributed across a number of architectural units. House 1 has been described as a coppersmith's workplace for purifying smelted copper and perhaps further reworking it (Weisgerber 1981:192). It contained the base of a smelting furnace, near which was an irregular pit partly covered by an ashy layer, that contained small slag

Figure 2.14The hoard of planoconvex copper ingots found at Maysar 1 in House 4 (from Hauptmann 1985:Abb.61).

droplets, lots of charcoal, and small fragments of furnace, in addition to another pit filled with charcoal (Weisgerber 198Ob:82). House 4 contained a fireplace, a possible kiln (Weisgerber 198013:8 8), and a hoard of plano-convex copper ingots weighing about six kg (see Figure 2.14; Weisgerber l 9 8 1:192). Evidence for metallurgical activities also came from one area of House 6, separated from the rest of the house by a small wall. The main installation was a large oval fireplace with broken furnace fragments and copper slag and a great deal of ash (Weisgerber 1981:193). Copper ingot fragments were also recorded on the surface of House 31, which displayed two phases of use. In the earliest phase, a large storage vessel was dug into the ground, filled in its upper levels with charcoal. Other small pits were found nearby, one of which contained a large flat copper axe (Wesigerber 1980b:Abb. 78.5). The fact that these installations were related to copper smelting is only demonstrated indirectly, by material incorporated into the walls of the second phase of the house. These walls contained furnace, slag, crucible and mould fragments (Weisgerber 198013:8 8-89). Based upon the above evidence, Hauptmann (1985:114) has described copper production at Maysar 1 (see Figure 2.5) as being organized along "small workshop" lines, probably for domestic use. Some con-

Geology and Early Exploitation of Copper

47

Figure 2.1 5 The third millennium BCE copper-smelting settlement of Zahra l , in the Wadi Bani 'Umar al-Gharbi,Oman. Crosses indicate concentrations of furnace fragments (after Costa and Wilkinson 1987: Figure 35).

fusion is introduced by the fact that, amongst archaeologists who have discussed the organization of production, the term "workshop" has a number of incompatible definitions. Clearly, the Maysar 1 "workshops" discussed by Hauptmann agree with the use of the term as defined by Peacock (1982:9), but are better referred to as simply "production loci" using Costin's (2001:296) terminology. Regardless, surveys of third millennium BCE sites in the Wadi Fizh and Wadi Bani 'Umar alGharbi west of Sohar (see Figure 2.15) provide similar

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examples of smelting installations within the bounds of small sedentary agricultural villages (Costa and Wilkinson 1987:223), although such sites unfortunately remain unexcavated. However, reconstructions of the organization of copper production at Maysar 1 must account not only for the existence of specialized production loci (e.g. House l ) , but also for the agglomeration of a number of such production loci within the one settlement (i.e. Houses 1, 4, 6 and 31). Weisgerber, for example, has

contrasted the findings from Maysar 1 with those from a small test trench at the site of Maysar 6, about one km to the southwest. There, remains of smelting operations or pyrotechnology were absent from surface collections and excavated deposits, and animal bone was much more abundant. Weisgerber (1981:205) thus regarded Maysar 6 as a "Wohnsiedlung", in contrast to Maysar 1, which he characterized as a "Wirtschaftsiedlung". He regarded the apparent concentration of production in one site as a clear indication of the "social differentiation" of the Bronze Age population of the Maysar area (Weisgerber l 9 8 1:197). Although such conclusions remain to be thoroughly evaluated (excavations at Maysar 6 were very limited), the archaeological data indicate a concentration of individual production loci in the settlement at Maysar 1, which is suggestive of specialization at a level above the individual household or workshop. It is possible to summarize the situation, using the variables proposed by Costin. Firstly, the context of copper production at Maysar 1 seems to have been independent of any elite control. There is no evidence at the site for the existence of elites who could have controlled the output of a group of attached specialists. Of course, such elites could have lived in a different location, but, as discussed more fully below, the evidence for elites with coercive political, economic, or military powers in third millennium southeastern Arabia is very limited. Examining the concentration of production, it can be seen that copper smelting refuse was concentrated within a number of architectural units in both the northern and southern areas of Maysar 1. Hauptmann has suggested that each unit represented a "workshop", and it is clear that a number of distinct production loci existed at Maysar 1, each specifically oriented towards the extraction of copper. Looking at a larger scale, Weisgerber has contrasted the rich evidence for craft production at Maysar 1 with the apparent absence of such activities at the nearby contemporary site of Maysar 6, as a demonstration that production was nucleated in certain settlements. Regarding the scale of production, it seems that the size of individual production units was not particularly large, probably representing production by autonomous household units. It is, therefore, highly unlikely that workgroups were com-

posed of unrelated individuals. Finally, the apparent integration of copper extraction with subsistence activities at Maysar 1, although not conclusively demonstrated, does suggest that the intensity of production changed on a seasonal basis, indicating that copper extraction can have been only a part-time specialization for the inhabitants of the site. Using the typology developed by Costin ( l 9 91:Table 1.1),we would describe copper extraction at Maysar 1 as representing "community-based production". This category of specialized production is defined simply as "autonomous individual or household-based production units, aggregated within a single community, producing for unrestricted regional consumption" (Costin 1991:8). Such a reconstruction faces the problem that the intended market (local, regional, international) for the copper ingots produced at Maysar 1 is unknown, but the general division of production into a number of individual household units at Maysar 1 seems quite clear. Production systems similar to that which characterized primary copper extraction Maysar 1 have been described in other archaeological production typologies: for example, Van Der Leeuw's (1977:Table 1)category of "village industry". However, an adequate understanding of copper production in Bronze Age southeastern Arabia is unlikely to be achieved by examining only the evidence from Maysar 1. Indeed, both ethnography and archaeology have highlighted instances in which the production of a particular good was organized in very different ways within the one society. In the particular case of southeastern Arabia, field research has indicated that there were a few Umm al-Nar Period copper extraction sites much larger than Maysar 1 or sites in the Wadi Fizh. These larger extraction sites have thousands of tonnes of slag and, unlike Maysar 1 and Zahra 1, are not found within or directly associated with sedentary agricultural settlements. In fact, around 80 percent of the total 10,000 tonnes of Bronze Age slag recorded during German fieldwork came from only two sites: Tawi Ubaylah and Wadi Salh 1, each with approximately 4,000 tonnes of slag (Hauptmann 1985:95). The question that immediately arises is whether such differences in the amount of debris at extraction sites are indicative of differences in the organization of production. For

Geology and Early Exploitation of Copper

49

example, Hauptmann (1985:95) regards such sites as representing Bronze Age copper production at an "industrial" scale, in contrast to production on a smaller scale as typified by Maysar 1 and Zahra 1. Of course, Hauptmann's claims are only for output at an industrial scale, not for truly industrial production. In a strict sense, industrial production requires "industrialization" of the manufacturing process as occurred in eighteenth century Britain: the development of factories which produced full-time utilizing full-time specialists, and relied upon power other than that provided by humans or animals, such as water mills and steam engines (Peacock 1982:10). The requirement for nonhuman or animal sources of power indicates clearly that industrial copper production was not undertaken in Bronze Age Oman, and even the requirement for fulltime production is far from demonstrated in the Omani case, as has been shown above for Maysar 1. Costin's (2001:280) discussion of the ethnographic data on premodern production systems must once again be borne in mind, particularly her conclusion that "it is well to more seriously consider seasonality-and the ability to work year-round-in studies that assert high intensitylfull-time production." In assessing the evidence from Bronze Age Oman, the realization that production without "industrial" organization can nevertheless lead to very high levels of output (e.g. Burton 1984) is an important one. The location of two very large extraction sites, ca. 250 km apart towards the northern and southern ends of the copper-bearing Semail Ophiolite, is perhaps significant. Tawi Ubaylah in the north represents the closest copper source to the third millennium settlement agglomeration in the A1 AinIBuraimi oasis (Cleuziou 2003). One obvious reconstruction of non-industrial production at Tawi Ubaylah might see the site as representative of seasonal (or more sporadic) operations over several centuries, undertaken by household, kin or community groups from the nearby oasis during lulls in the agricultural cycle. Parallels for such a mode of production can be drawn with the long-term, intensive, seasonal exploitation of other localized resources in the Oman Peninsula, such as the processing of marine resources at the Bronze Age site of Ra's al-Jinz 2 (Cleuziou and Tosi 2000). Looking further afield, V. Pigott's (1998)analysis of Bronze Age copper production in Thailand has utilized

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ethnographic studies of stone quarrying (Burton 1984) to suggest that production at a very large scale could result from repetitive exploitation (every few years) by cooperative kin or residence-based groups within tribal societies. Moreover, Muller's (1984)study of salt production in preColonial North America indicates that a large quantity of production refuse can accumulate at a production site that was probably exploited by non-specialist producers on a seasonal basis, but over a very long period of time. Muller's study demonstrates the crucial distinction between site specialization and producer specialization that must be made when investigating prehistoric production systems. Therefore, the much greater scale of production at Tawi Ubaylah in comparison to a site like Maysar 1 could represent one or a combination of numerous factors. It may reflect a different mode of production, a more intensive and larger-scale production made possible by the greater size of the workforce from the A1 AinIBuraimi oasis available for mining and smelting. It has been ethnographically observed that increasing community size not only provides the potential for greater output, but also allows for more diversity in the types of specialized production practiced by the polity as a whole (Costin 2001:274). However, a similar agglomeration of Bronze Age population cannot currently be documented for the Wadi Salh 1 region. Alternatively, as basic questions regarding the duration of smelting operations at Bronze Age sites remain unanswered, the greater scale of smelting debris at Tawi Ubaylah and Wadi Salh 1 might simply reflect production over a longer period. These sites could represent examples of "site specialization" as defined by Muller. Certainly, given the lack of published evidence for habitation remains in the vicinity of Tawi Ubaylah, its status as a specialized production site, or "limited activity" area is clear. This is interesting, as sites such as Maysar 1 and Wadi Fizh 1 have been regarded as full-activity sites, where metal extraction was integrated with daily and seasonal subsistence activities (see above). In general, the fact that some extraction sites are associated with permanent settlements and others are not suggests that there was more than one mode of specialized copper production in Bronze Age southeastern Arabia.

In discussing this issue, an accurate understanding of the socio-political organization of the region in the third millennium BCE is critical, as indigenous social and political formations no doubt influenced the nature of primary extraction (e.g. O'Brien 1998; Pigott 1998).Of course, the relationship between social organization and production is not determinative, but "with increasing social complexity the potential for complex procurement systems is enhanced" (Pigott l998:215). More generally, Costin (1991:2)has observed that a true understanding of the organization of a production system requires an understanding of both the natural and social contexts in which it operates. It is well established that the third millennium in southeastern Arabia witnessed an increase in the level of economic articulation and integration between local farming, fishing, and herding communities (e.g. Cleuziou and Tosi 1989).Such integration is usually regarded as having been strongly affected by prevailing environmental conditions, particularly the intense localization of productive natural resources in the Arabian peninsula that necessitated the development of connections between groups of specialized producers and the emergence of "trade as a subsistence activity" (Afanas'ev et al. 1996; see also Cleuziou and Tosi 1989; Cleuziou and Mkry 2002; Piesinger 1983:709). Regardless of its underlying causes, it is clear from the distribution and small size of known Umm al-Nar Period settlements (contra Orchard 1995; Orchard and Stanger 1994),and the limited adoption of administrative tools such as stamp seals (Cleuziou and Tosi 2000:59-63), that economic integration was not accompanied by the development of a state-like political structure (Crawford l998:138; Cleuziou 2002:225). In fact, the socio-political organization of southeastern Arabia in the third millennium has most commonly been compared to that of the ethnographically-documented, kin-based, tribal groups of that inhabited the region into modern times (e.g. Cleuziou and Tosi 1989:17; Cleuziou 2003:140; Cleuziou l996:162; Crawford 1998:140). Following such a reconstruction, the Umm al-Nar Period villages built around one or a small number of stone and mudbrick towers are best seen as the manifestation of a polycentric distribution of power between numerous, competing petty sheikhs or rulers (cf. Edens and Kohl 1993:25-26; Edens 1992:128).

Support for such a reconstruction is provided by the analysis of funerary evidence from southeastern Arabia and by Mesopotamian historical texts. In the cuneiform sources, sporadic references to "kings" of Magan in the third millennium (Potts 1990a:137, 144) suggest a higher degree of social hierarchy in the southern Gulf region than indicated by the material record. However, these texts are probably best seen as resulting from either the "inflationary" tendencies of Mesopotamian royal inscriptions (distorting the standing of their eastern counterparts in order to increase the prestige of military victories and trade relationships, cf. Heimpel 1987:44; Kohl 2001: 228-229), or as reflections of short-lived military coalitions formed in response to Mesopotamian aggression (Cleuziou 1996:161). Regarding the funerary evidence, while the rich burial goods found in Umm al-Nar Period graves such as at Tell Abraq (Potts 2000) are suggestive of differences in wealth or status amongst members of the community, the collective nature of burial may reflect strong ideological sanctions operating against the formation of entrenched political hierarchies. However, as stated by (Cleuziou 2003:141): This strong manifestation of 'equality' inside the community should not be taken as testimony of a strictly egalitarian society, but rather as an ideological affirmation beyond diversity and power amongst the living. Tosi, Crawford (1998) and Cleuziou (2002,2003) clearly regard Umm al-Nar Period burial practices as emphasizing a social system based around membership of kinship groups, or "corporate lineage groups of common descent" (Tosi 1989:155). Leadership is conceived of as proceeding by negotiation and the manipulation of "an intricate web of matrimonial, economic and social relations" (Cleuziou 2003:145) rather than the possession of significant coercive power. The increasing complexity in Bronze Age southeastern Arabia can thus be seen as having developed more strongly along heterarchical rather than hierarchical lines. Significantly, a number of scholars have stressed the importance of interregional exchange and economic specialization in the horizontal integration of such competing polities (e.g. White and Pigott 1996: 170). Production and exchange of commodities in the region did indeed intensi-

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51

fy in the Umm al-Nar Period (e.g. Afanas'ev et al. 1996; Cleuziou and Tosi 2000:26), and there is evidence for increasingly specialized production: pottery manufacture in the Hili oasis and wider Oman (Miry 1996, 2000); soft-stone vessel manufacture at Maysar 1 and elsewhere (Weisgerber 1981; David 1996), and shell rings in the Ra's al-Jinz and Ra's al-Hadd regions (Charpentier 1994; Cleuziou and Tosi 2000:35). This aspect of regional specialization and inter-regional exchange has been addressed above, where the discussion focused upon Ricardo's Law of Comparative Advantage as the economic force underlying the development of specialized production at the community and sub-regional levels. Funerary pottery, soft-stone vessels and shell rings seem to have been manufactured under household or community-based modes of production. The evidence for copper production at Maysar 1 fits comfortably within this model of geographically-localized production for distribution within southeastern Arabia, but the large sites of Tawi Ubaylah and Wadi Salh 1 raise other possibilities.

Finally, in comparing Bronze Age copper extraction with the production of items such as pottery, shell rings, and soft-stone vessels, we must remain cognizant of the major differences between the scale of demand for Omani copper and these other commodities. Although some Omani pottery vessels and soft-stone vessels were traded overseas, particularly to the central Gulf region (Miry 2000; David 1996), pottery, soft-stone and shell rings were produced predominantly for consumers within southeastern Arabia. Copper, on the other hand, although utilized locally in undoubtedly large quantities, may at certain times or locations have been produced predominantly for foreign markets. The great differences in scale of Omani smelting sites might therefore be a reflection of production for different consumers, with different scales of demand. A parallel for this situation can be drawn with archaeometallurgical reconstructions of Iron Age copper exploitation on Cyprus, where very large copper extraction sites are also found to be contemporary with extraction on a much smaller,

Figure 2.16 An Iron Age slag heap at Raki 2, Oman (after Wesigerber and Yule 1999: PI.4).

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Early Metallurgy of the Persian Gulf

"workshop" scale. It has been hypothesized that the large-scale extraction on Cyprus might be for export, while workshop production is focused towards local consumption (Kassianidou l998:23 8). As can be seen from the above discussion, the archaeological evidence for the organization of copper extraction in Bronze Age Oman is so minimal as to make hypothesizing over modes of production a rather difficult undertaking. The evidence for copper production at sites such as Maysar 1, Zahra 1, and Wadi Fizh 1 suggests household or workshop production loci agglomerated at an extra-household level: a village or community-based craft. The evidence from Tawi Ubaylah and Wadi Salh 1 is equivocal, especially given the complete lack of evidence regarding the duration of operations at either site, and the number of production units that may have simultaneously operated at each. Nevertheless, the scale of production at Tawi Ubaylah and Wadi Salh 1 suggests the possibility of copper extraction at the extra-community level. There is no evidence from the Umm al-Nar Period for any long-lived political hierarchy that may have emerged to control such a production system, although at least one ethnographic study of stone quarrying (Burton 1984) has demonstrated that such leadership is not essential to coordinate production within a large, kin-based, tribal groups. Clearly, more fieldwork will be required to elaborate our understanding of the organization of copper production in third millennium southeastern Arabia. Organization of Production in Later Periods The same issues can be raised again in regard to copper production in Iron Age southeastern Arabia, although unfortunately at this time there is even less evidence from archaeometallurgical studies to support the archaeological data. In contrast to what appears to have been the predominant integration of third millennium copper production within villages concerned with agricultural and pastoral subsistence activities, surveys in Wadi Fizh suggest that a different relationship may have existed in the Iron Age (Costa and Wilkinson 1987:225, 232). Iron Age settlements in the region show much less evidence for primary copper extraction, whist the enormous size of Iron Age slag heaps at sites such as Raki 2 (ca. 45,000 tonnes; see Figure 2.16) and Tawi Raki 2 (ca.

40,000 tonnes) indicates that production levels are perhaps many times higher than in the Umm al-Nar Period (see above). Furthermore, Iron Age mining and smelting for the first time dealt with ores from the massive sulfide deposits: both the low grade secondary mineralization of the gossans and the sulfidic ores of the unweathered ore body (Weisgerber 1987, 1988; Hauptmann 1985:Abb. 85). These deposits are much larger than those exploited in the third millennium BCE, and fewer in number. Thus, we have a situation whereby higher levels of production were undertaken at a limited number of larger copper ore bodies, and intensive, even full-time production seems much more probable. The apparent functional distinction of Iron Age settlements into agricultural and smelting sites, which more closely parallels the situation of the early Islamic period, may reflect such a mode of production, although further field research will be required to adequately address this issue. Production is certainly on a large scale, but whether it is organized at a community or extra-community level is almost impossible to determine given our limited information on the scale of smelting operations at any one time, their chronological duration within the Iron Age, and the possibility of seasonality in production. Interestingly, although levels of copper production are significantly higher in the Iron Age than in the third millennium, the political organization of the region seems similar: there is no evidence for development of a clear settlement hierarchy, large public buildings, or a state-like level of complexity. Despite rare references to "kings" of the region in cuneiform sources, the distribution of power is still generally characterized as polycentric (e.g. Magee 1999). Clearly, the high output of copper in Iron Age southeastern Arabia reflected the economic complexity of the region rather than its political stratification. As for most other categories of information related to copper extraction in southeastern Arabia, the best evidence for the organization of production comes from the early Islamic Period. Reconstructions of output at this time indicate clearly that copper was produced on an industrial scale, although not classifiable as "industrial" following the strict definitional requirements of the term outlined above. Individual mining and extraction sites such as Lasail have up to 100,000 tonnes of slag; the total amount of early Islamic slag reported from Oman

Geology and Early Exploitation of Copper

53

is more than half a million tonnes; and the estimated total copper production is 60,000 tonnes over a period of only a century (see above). Our understanding of the organization of this industrial-level production is informed by a small number of historical sources, which provide fragmentary evidence for trading, contractual arrangements, taxes and administration Archaeological survey and excavation have delineated the settlement structures associated with mining and smelting sites, and indicated the physical mechanisms by which copper production was organized and controlled at the extraction sites themselves. Basic settlement structures with storage areas for crucial elements of production and subsistence, such as water and charcoal, are known from 'Arja, Lasail, Samdah, Mullaq, Wadi asSafafir and other sites (Weisgerber l98O:ll8; Ibrahim and El Mahi 1998). Most houses seem to have been concentrated into residential areas or villages in the vicinity of the mines themselves, however different arrangements were also seen. For example, at 'Arja production seems to have been organized into units, in which one house seems to be related to one mine, smelting furnace and slag heap, and there is no evidence for the existence of an accumulation of dwellings in one area to form a "village" (Weisgerber 1987:158). Utilizing the evidence from early historical sources, these mining units are interpreted as the remains of a production system in which each miner (and perhaps additional kin) exploited his own mine, essentially independently (Weisgerber 1987: 158). Unfortunately, no historical texts survive which discuss the organization of smelting, as opposed to mining. Other aspects of settlement in the early Islamic mining regions, such as mosques, graveyards and extensive architectural features related to agricultural water management, have also been recovered archaeologically (Weisgerber 1980:118; Ibrahim and ElMahi 1998:132). Additionally, the presence of large, fortified buildings in prominent and defensible locations (such as on hills, high terraces, or at the entrance to the mining wadis) at many early Islamic sites has been used to suggest the presence of people who had some role in the control or protection of the mining district (Weisgerber 1980:117). The function of Sohar as the outlet for the majority of copper produced in the Wadi al-Jizzi area is also supported by historical documentation (Whitehouse

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Early Metallurgy of the Persian Gulf

1979:874; J. C. Wilkinson 1979:892), and by archaeological evidence from Sohar itself (Williamson 1973:16 and Figure 3a). A contextualization of the evidence for early Islamic copper production with other archaeological and historical evidence is far from complete, although efforts at defining the inter-relationship of settlement and copper exploitation in the hinterland of Sohar have been undertaken (Costa and Wilkinson 1987; Ibrahim and El Mahi 1998). It is clear that copper production and agriculture were specialized activities carried out in separate areas, leading to inter-dependence between Sohar and its mining hinterland (Costa and Wilkinson 1987:232).

Copper-Base Objects in Bronze Age Southeastern Arabia Having examined the evidence for primary copper extraction, we turn now to the evidence of how such metal was utilized locally in the production of finished objects. This section will focus predominantly on the types of finished objects that were produced, rather than on the technology of their production, as evidence for secondary refining and fabrication at Umm al-Nar Period sites is slim and understudied. As summarized in Weeks (1997:17-20), the most extensive evidence comes from Umm an-Nar Island, where crucible and mould fragments and numerous metallic refining and casting residues attest to the melting and refining of raw copper produced further inland. Metalworking areas have also been recorded at Hili 8, in Periods IIe and IIf (ca. 2500-2000 BCE), and small quantities of refining and casting debris are found as early as Phase Ib (ca. 2900 BCE) at the site (Cleuziou 1980, 1989). At Tell Abraq, there is abundant evidence for metalworking in the second and first millennia BCE, but Umm al-Nar Period metalworking debris is limited to a single amorphous metal lump dated to the terminal third millennium (Weeks 1997:28). The evidence from sites such as Bat (Frifelt l979:584) and Ghanadha (A1 Tikriti 1985:16), where surface finds of copper-base scrap are said to be numerous, remains unstudied. The earliest copper-base objects in southeastern Arabia appear in the late fourth and early third millennia BCE, at middens and settlements such as Wadi Shab GAS1, Ra's al-Hadd and Ra's a1 Hamra (Durante and

Tosi 1977; Uerpmann 1992:97; Cleuziou 1996:160; Tosi and Usai 2003:20), at Hili-8 Period Ib, where copper working debris is also recorded (Cleuziou 1989:Pl. 33), and in contemporary beehive and Hafit-type burial cairns (Frifelt 1971, 1975b; Benton and Potts, 1994). Interestingly, the earliest use of copper-base objects at Wadi Shab GAS1 and Ra's al-Hamra, although significantly later than seen in the neighboring regions of Mesopotamia, Iran, or Baluchistan, occurs in local material assemblages which are still pre-ceramic. The objects produced at this period are simple tools, such as small blades, fish hooks and pinslawls, that occur in small numbers on coastal sites with a strong orientation towards seasonal exploitation of marine resources (Cleuziou and Tosi 2000:26-27). The metal objects from Hafit tombs include a number of copper-base items such as blades, rivets, tweezers and long awls or "eye-pencils" (Frifelt 1975b:61-67, Figures 3, 5; Frifelt 1971:Figure 12; Cleuziou and Tosi 2000:26) commonly associated with bi-conical pottery of the Mesopotamian Jemdet Nasr tradition. The technology of this copper use remains uninvestigated, and it has not been demonstrated whether these earliest metal objects were made from local or imported copper. The considerable evidence for later Urnm al-Nar Period copper production in the region makes it likely that they represent the products of the earliest copper extraction in southeastern Arabia. This theory is supported by Frifelt (1975b:69), who suggests that by the early third millennium, "the grave builders of BatIIbri and Buraimi were all engaged in the copper trade from inner Oman with Buraimi as a market place at the crossroads and Urnm an-Nar as one of their shipping places". Occupation on Urnm an-Nar Island is thought to have begun at around 2700 BCE, and continued to as late as 2200 BCE (Frifelt 1995:237-239). The inventory of copper-base objects from the collective tombs on the island is limited to simple tanged or riveted knives and daggers, pinslawls and fish hooks (Frifelt 1991:98-103). All the excavated pinslawls come from Grave V, regarded as earlier in date than material from Graves I, I1 and V1 (Frifelt 1991:125), although virtually identical objects are recorded in later Urnm al-Nar Period tombs at A1 Sufouh (Benton 1996:Figure 192) and Hili North Tomb A (Cleuziou and Vogt 1985:Pl. 28). Settlement contexts

on Urnm an-Nar Island produced a similar array of objects to that found in the graves, including fish hooks, knivesldaggers, pinslawls, chisels, "borers" (hollow cone-shaped points), and a blade axe. In addition, there is evidence for metalworking in the form of copper ingot fragments, clay moulds, processing resides and crucible fragments (Frifelt 1995:70, 188-191, Figures 108-118, 263-280). A very similar array of copper-base objects has been recovered from the seasonal Urnm al-Nar Period settlement of Ra's al-Jinz (RJ-2) in the Ja'alan, which also has evidence for the secondary working of copper (Cleuziou and Tosi 200054-57, Figures 12-14). Copper fish hooks, in particular, seem to be ubiquitous at coastal sites from the third millennium BCE onwards; they are recorded in their hundreds at RJ-2 (Cleuziou and Tosi 200054) and known from sites as distant as Urnm an-Nar Island and SWY-3, located near Suwayh on the Arabian Sea (Mery and Marquis 1998:220-223 and Figure 10). Overall, fish hooks, pinslawls, and blades typify the copper-base objects found in third millennium settlement sites of southeastern Arabia, and indicate a basic metalworking technology aimed at the production of simple and functional tools necessary for everyday subsistence activities. The practice of metalworking within settlements at this time is attested by pieces of copper scrap and working debris found at sites such as Hili-8, RJ-2, Bat and Tell Abraq (Cleuziou 1989; Cleuziou and Tosi 2000:54-59; Frifelt 1979584; Weeks 1997). As noted above, these metalworking operations are largely unstudied, but they likely included melting, casting, and secondary refining to remove impurities from raw copper, but not primary smelting. A more diverse array of copper-base objects, in terms of typology, size, and perhaps metalworking technology, is found in graves of the later Urnm al-Nar Period. Finger, toe, and earrings become a particularly common find category, for example at Hili North Tomb A (Cleuziou and Vogt 1985:Pl. 28), Hili Tomb N (AlTikriti and Mery 2000:213 and Figure 10), A1 Sufouh (Benton 1996:Figures 194-195), Moweihat (Haerinck 1991) and Tell Abraq (Potts 2000:77). A number of examples of flat "razors" are also known from Hili Tomb N and Hili North Tomb A (Al-Tikriti and Mery 2000:Figure 10; Cleuziou and Vogt 1985:Pl. 28.1), Tell Abraq (Potts 2000:76), and Ra's al-Jinz (Cleuziou and

Geology and Early Exploitation of Copper

55

Tosi 2000:Figure 15). The very end of the third millennium witnesses the introduction of the socketed spearhead, as found in the Asimah grave alignment (Vogt 1995) and in large numbers in the Tell Abraq tomb (Potts 2000:68-69). This type continues in use into the Wadi Suq Period, as seen by its occurrence in graves at Shimal (Vogt and Franke-Vogt 1987:Figure 21), AlWasit (Al-Shanfari and Weisgerber 19895'1. 5), Ghalilah (Donaldson 1985:Figure 28), Bidyah (A1 Tikriti 198913: PI. 73) and Ghanadha Island (Al-Tikriti 1985:Pl. 16). While some continuity is thus seen between the metal assemblages of the third and second millennia BCE in southeastern Arabia, the Wadi Suq Period and Late Bronze Age also witness the introduction of new forms of weaponry. Examples include the long copperbase swords found in collective burials at Al-Wasit, Qattarah and Qarn Bint Saud (Cleuziou 1981:Figure 12; Al-Shanfari and Weisgerber 1989:Pl. 5; Potts 1990a:252 and Figure 29), and tanged arrowheads, often with incised decoration, which appear at sites across the peninsula from the mid-second millennium onwards (Magee 1998a). Additionally, copper- base vessels, which are extremely rare in third millennium contexts in southeastern Arabia (e.g. Vogt 1995:Figure 55), appear more frequently in tomb assemblages of the second millennium BCE (e.g. A1 Tikriti 1989:Pl. 70-72). A limited amount of compositional analysis of third millennium BCE metalwork has been undertaken, including fully-quantitative and semi-quantitative analyses of objects from Umm an-Nar Island (Berthoud 1979; Frifelt 1975, 1990; Craddock l 9 8 1; Hauptmann 1995; Prange et al. 1999), sites in A1 Ain (Berthoud 1979) and the Wadi Samad (Hauptmann et al. 1988), and Tell Abraq (Weeks 1997; Pedersen and Buchwald 1991). The great majority of analyses have indicated that tin-bronze was very rarely used at Umm al-Nar Period sites in southeastern Arabia. Objects were predominantly of copper, with the elements arsenic and nickel occurring in quantities of up to four percent or higher, a pattern of impurities generally consistent with contemporary ingot and raw copper fragments from Maysar 1, Wadi Bahla, Umm an-Nar Island and Ra's al-Hamra (Hauptmann 1987, 1995; Hauptmann et al. 1988; Craddock 1981). As has been noted previously, the Tell Abraq analyses contrast strongly with this pattern; tin-bronze was used

56

Early Metallurgy of the Persian Gulf

for more than half of the 31 analyzed objects from Umm al-Nar Period settlement and funerary contexts at this site (Weeks 1997). The only other tin-bronzes reported from this period are isolated examples from a tomb at Hili (Berthoud 1979:Table 5), two objects from unspecified sites in the region (Prange et al. 1999:Figure 6), and beads from Ra's al-Hadd (personal communication J.E. Reade). Evidence for the local working of tin-bronze is also provided by the analyses of a piece of metalworking debris from Hili-8 Period IIf, which contained ca. 0.5 percent tin (Cleuziou 1989:74). Nevertheless, the first significant appearance of tinbronze in southeastern Arabia is still sometimes claimed to occur only in the second millennium BCE (e.g. Prange et al. 1999), before it becomes the dominant alloy in the local Iron Age, as represented by the analyses of objects from the IbriISelme hoard (Prange and Hauptmann 2001). However, compositional variability between individual assemblages seems to be a feature of southeastern Arabian metallurgy, making chronological distinctions in alloy use hard to support. For example, the analyses presented in this volume clearly support the findings of the Tell Abraq study regarding the use of tin-bronze in the third millennium BCE in the northern part of the Oman Peninsula. Such results cannot be used to push back the "introduction" or "origin" of tin-bronze in the region, however, as later assemblages such as that from the early second millennium Qattarah tomb contain no tin-bronze objects (Cleuziou l 9 8 l:288). Likewise, the total dominance of the tin-bronze alloy in the southeastern Arabian Iron Age suggested by analyses of the IbriISelme hoard is not evident at the Iron Age settlements of Tell Abraq and Muweilah, where only one-quarter of finished objects are of tin-bronze (Weeks, forthcoming b:Tables 3 and 4; 1997:Table 7). The adoption of tin-bronze technology in southeastern Arabia is a complex issue which will be discussed at length in the following chapters. Alloys other than tin-bronze and AsINi-copper are extremely rare in southeastern Arabia before the end of the Iron Age. The exception concerns a group of ten objects from collective graves on Umm an-Nar Island, analyzed by both X-ray diffraction and atomic absorption spectrometry (Frifelt 1991:lOO). Eight of the objects contained significant amounts of zinc, in the two to 10 percent range, sometimes occurring in addition to other

elements such as nickel and arsenic (one to two percent), and lead (up to 25 percent). The two remaining objects also contained high lead concentrations, in the three to 11 percent range. While these objects are compositional rarities in third millennium southeastern Arabia, and generally in wider western Asia, they are paralleled in compositional terms by a number of contemporary shaft-hole axes from the Royal Cemetery at Ur, dated to the ED 111-Early Akkadian Period (Miiller-Karpe 1989:Table 1 and Abb. 6). Additionally, broadly contemporary copper-base objects with significant zinc and lead concentrations are reported from the Aegean site of Thermi, on the island of Lesbos (Begemann et al. 1992, 1995; Stos-Gale 1992), and from the site of Ikiztepe on the Black Sea coast of Turkey (Bilgi 1984). The use of other metals is first documented in the later Umm al-Nar Period, by the appearance of numerous silver beads of various shapes from Tell Abraq, Hili North Tomb A (Cleuziou and Vogt 1985:33), and Moweihat (A1 Tikriti 1989a:95, PI. 56c), as well as gold beads, a ring, and two gold animal pendants (one in the form of a ram and the other depicting a pair of longhorned caprids) from Tell Abraq (Potts 2000:54). There is also a small gold object from Cairn X on Umm anNar Island (Berthoud and Cleuziou 1983:243). The tradition of animal-shaped pendants in precious metals continues into the Wadi Suq Period, where similar examples in gold, electrum and silver are known from tombs at Qattarah (Cleuziou 1981:Figure 13), Bidya (Al-Tikriti 1989b:Pl. 74a) and Dhayah (Kastner 1991). Iron objects have not been found in the region before the middle of the local Iron Age, and even then occur only rarely (Magee 1998b; 2002:Figure 2; Magee et al. 2002:Figure 30).

Summary Archaeometallurgical work in southeastern Arabia has been inspired predominantly by Mesopotamian historical accounts of trade and traders in the Persian Gulf. One cannot but be impressed by the scale of the Dilmun copper trade in the early second millennium BCE recorded in cuneiform documents, or by references to the "copper mountain" of Magan where the majority of this metal seems to have been produced. Since the 1970s, geological and archaeological surveys in southeastern Arabia have recorded more than 150 copper

deposits mountainous regions of the interior, and have demonstrated the importance of the region as a copper producer in the ancient world. Omani copper deposits are found principally in rocks of the Semail Ophiolite complex, a piece of ancient oceanic crust that was obducted onto the mainland Arabian Plate between 90-70 million years ago. The largest copper deposits in the region are found in the upper extrusive sequence of the Semail Ophiolite, at sites such as Bayda, Lasail, 'and Raki, and consist of massive sulfide deposits with brightly colored gossans containing low-grades of secondary copper mineralization (oxides, carbonates and sulfurbearing species). The copper minerals found in the gossans of these deposits could have been exploited in the Bronze Age, although some evidence indicates that the systematic exploitation of the gossan ores began at the same time as the first large-scale exploitation of the unaltered primary massive sulfides, i.e. in the Iron Age. Many copper deposits with intensive areas of secondary mineralization exist in the lower units of the Semail Ophiolite, and these ores are regarded as being of paramount importance for Bronze Age smelting operations in southeastern Arabia. Significantly, Bronze Age copper mining is also known to have taken place in the Masirah ophiolites, which are a geologically similar but unrelated formation located on Masirah Island off the south coast of the Sultanate of Oman. A number of small copper deposits have also been recorded in rock units of the mainland that are older than the Semail ophiolite. Following from the results of geological survey in southeastern Arabia, work by the German Mining Museum in the Sultanate of Oman since 1977 has clearly demonstrated that metallic copper was produced in large quantities as early as the Umm al-Nar Period. The German analyses strongly support the hypothesis suggested on archaeometallurgical grounds as early as the 1920s by the Sumerian Copper Committee, and later supported by the provenance analyses of the French CNRS: the mountains of the northern Sultanate of Oman and the U.A.E. are the source of the copper of Magan. Production seems to have peaked in the later third millennium, when a few thousand tonnes of copper were produced for local use and foreign exchange. Specialization in copper production is clearly observed at this time, with a number of settlements providing evi-

Geology and Early Exploitation of Copper

57

dence for production units organized along household or "workshop" lines, nucleated within individual agricultural villages. Two larger smelting sites suggest the possibility of more intensive copper extraction, but critical archaeological evidence regarding the duration and intensity of production is absent, making conclusions regarding multiple modes of Bronze Age primary copper production impossible to verify. Bronze Age copper production in southeastern Arabia witnessed distinct periods of growth and decline, which can be correlated with a number of technological, environmental, and socio-economic factors. While there is little evidence for the direct adoption of a developed smelting technology from Iran or Baluchistan, the possibility that the idea of copper extraction arrived via stimulus diffusion from the north is plausible. Local extraction appears to have begun in the late fourth or early third millennium BCE and there was a significant increase in output over the course of the third millennium. Increased Umm al-Nar Period production is correlated with a growth of local population and settlement, greater economic integration within southeastern Arabia, and increasing intensity in maritime exchanges with polities in Mesopotamia, Iran, the central Gulf and the Indus region. In a similar manner, the apparent decline in copper production in the early second millennium BCE is correlated with a decline in the internal economic integration of southeastern Arabia, the collapse of the Gulf trade, and perhaps environmental degradation exacerbated by excessive wood harvesting for smelting. While most studies of copper production in the region have stressed the importance of foreign markets in determining copper production levels in southeastern Arabia, it is clear that the scale and integration of the local southeastern Arabian economy was also critical in determining levels of copper extraction and exchange in the Bronze Age. In contrast to the large-scale primary extraction that characterized the Umm al-Nar Period, the object analyses and descriptions presented earlier in this chapter demonstrate little in the way of elaborate metalworking techniques. Local metalworking industries were characterized by a relatively limited array of simple tools related to everyday subsistence activities, such as fish hooks, pinslawls, and basic blades. Assemblages of metalwork

58

Early Metallurgy of t h e Persian Gulf

from contemporary funerary contexts demonstrate a wider repertoire, including non-utilitarian objects such as rings and beads, in addition to weapons such as spearheads. Compositional analyses have indicated that, in addition to local copper and copper alloys, foreign metal was utilized in significant quantities at least one site (Tell Abraq) in the northern Oman Peninsula and perhaps in more limited quantities at other Umm al-Nar Period sites. The potential importance of this foreign metal for the local Omani metalworking industry, its likely sources, and its use in southeastern Arabia outside the settlement of Tell Abraq, will be discussed at greater depth in the later chapters of this volume.

3

Analyzed Artifacts: Contexts and Chronology

This chapter presents background stratigraphic, chronological and contextual information on the metal samples that are analyzed in this volume. A total of 83 copper-base objects of Urnm al-Nar date were analyzed using PIXE, in addition to the analysis of one tin ring by EDS. All objects of Urnm al-Nar Period date analyzed compositionally come from funerary contexts. Material was obtained from four sites, including Urnm al-Nar-type tombs at A1 Sufouh (Dubai Emirate) and Tell Abraq (Sharjah Emirate), and two Urnm al-Nar tombs known as Unarl and Unar2 near the village of Shimal (Ras al-Khaimah Emirate). Approximately 20 copper-base objects have been analyzed from each of the tombs, and efforts have been made to analyze objects of varied typology from each assemblage. The chronological ranges of the sites are shown in Figure 3.1, and are discussed more fully below.

Excavation of one occupation area (Area B) to the north of the Urnm al-Nar tomb revealed the edge of an extensive area of cooking hearths. Material from excavated deposits consisted primarily of burnt marine shell and fish bones, in addition to a number of ceramic sherds datable typologically to the Urnm alNar Period. The Urnm al-Nar ceramics suggest that occupation in Area B was at least partly contemporary with the construction and use of the tomb at A1 Sufouh, although two sherds of Barbar pottery discovered during excavation indicate continued occupation or re-occupation in the early second millennium BCE (Weeks 1996). It has been suggested that the site represents a seasonal camping ground that must have been utilized over a significant period of time. As such, the site is comparable to other ephemeral third millennium coastal settlements on the southern Gulf shores, such as Ras Ghanadha (al-Tikriti 1985). All the analyzed copper-base samples from A1 Sufouh come from the main Urnm al-Nar tomb at the site (Tomb I), shown in Figure 3.2. The tomb is a typical example of Urnm al-Nar Period funerary architecture: it is circular, with a diameter of 6.5 m, and divided into six internal chambers. Both the ringwall and the internal walls are made of unworked stone blocks, although the ring-wall is faced with a single layer of well-masoned ashlars (Benton 1996:Figures 21 and 23). A significant amount of human skeletal material was excavated from within the tomb itself and from three pits that were dug in the vicinity of the tomb (Tombs 11-IV). The estimated

-

AI Sufouh The archaeological site of A1 Sufouh is located about one km from the modern shore of the Gulf, on the southern outskirts of the city of Dubai. The site, discovered in 1988, consists of a number of distinct, low mounds with evidence for human occupation in the form of ash, shell, bone, pottery and other artifacts (Benton 1996:20). Significant areas of the site were destroyed during recent construction activities, however a number of occupation areas and a round, stone-built, Urnm al-Nar-type tomb survived and were the subject of rescue excavations in mid-l 994 (Dubai Museum) and a thorough excavation in early 1995 (University of Sydney, see Benton 1996).

Tell Abraq Unar2

-Illlllllllllllll

Unarl AI Sufouh I

I

1

I

I

I

I

I

2700 2600 2500 2400 2300 2200 2100 2000 1900 1800

Years BCE

Figure 3.1 Chronology of the tombs from which the copper-base objects analyzed in this volume were excavated.

number of individuals interred at the site is 121, with a MNI of 1 3 people calculated for Tomb I (Benton 1996:49). Over 60 ceramic vessels have been recovered from all burial contexts at A1 Sufouh, including at least 20 examples of black-on-red Umm al-Nar style pottery and three Iranian black-on-gray vessels from Tomb I (Benton 1996:Figure 129). Further examples of Iranian gray-wares were found in Tomb 11. Nearly 14,000 beads were recovered from burial contexts at the site, over 90 percent of which were of serpentinite or talcose steatite (Benton 1996:Figures 133-1 35, Table 10). However, other materials such as soft-stone, shell, rock crystal and agate were also found, in addition to approximately 300 carnelian beads (nine of which were etched) and two lapis lazuli beads. Three lapis lazuli pendants were also recovered (Benton 1996:Figure 198). Copper-base objects such as blades, rings and pins or awls were also recovered (Benton 1996:Figures 183-195). The excavated material from A1 Sufouh suggests that the tomb was built and used in the middle of the Umm al-Nar Period. In particular, the lack of se'rie re'cente soft-stone vessels in the tomb assemblage suggests that the tomb deposits pre-date the manufacture of such objects in southeastern Arabia, which Benton (1996:Table 17) places at ca. 2300-2000 BCE. The black-on-red and grayware ceramics from the tomb suggest deposition sometime shortly after the middle

of the third millennium BCE, and Benton (1996:Figure 204) has proposed a chronological range for the use of the tomb of ca. 2450-2300 BCE. The copper-base objects from A1 Sufouh analyzed in this volume are listed in Table 3.1 and some are illustrated in Figure 3.3. As can be seen, only samples from Tomb I were analyzed, all of which were found in the western half of the tomb. Only material that was already fragmentary was sampled, meaning that daggers and blade fragments were analyzed but no rings or pinslawls. The group of analyzed samples is thus a biased one in terms of object types. Additionally, there is the possibility that the 22 analyzed fragments may have come from less than 22 objects. A total of 35 copper-base finished objects were recovered from the A1 Sufouh burials, including 22 from Tomb I, as well as numerous unidentifiable metal fragments (Benton 1996: 145). Fourteen dagger blades are recorded from all burial contexts at the site, and it must be remembered that material found in Tombs 11-IV could once have been interred in Tomb I and have left fragmentary remains there (although this view is contradictory to the chronological associations proposed by Benton (1996), see Kennet (1998) for an alternative view). Comparisons of PIXE data (see Chapter 3) for the fragments indicate groups of samples with very similar composition, but these are as likely to reflect a common metal source (whether ingot or mine) as a common object.

Figure 3.2 AI Sufouh Tomb I after excavation, seen from the west (photo courtesy of Daniel Potts).

60

Early Metallurgy of the Persian Gulf

Unarl The archaeological sites of Shimal lie about eight km northeast of the modern city of Ras al-Khaimah, at the foot of the limestone mountains which comprise the Musandam Peninsula near the modern village of Shimal (Vogt and Franke-Vogt 1987:Figure 2). The Umm al-Nar Period tomb designated Unarl was excavated by the German Mission to Ras al-Khaimah in 1988 (Kastner et al. 1988), and remains largely unpublished. A preliminary report on the discovery and excavation of the tomb (Sahm 1988) provides basic information on the cultural and skeletal material found, and on architectural, taphonomic and chronological issues. The tomb is a relatively large example of typical Umm al-Nar type: circular (with a diameter of 11.5 m), stone-built on a low plinth wall, and divided internally into eight chambers by a north-south running dividing wall and three east-west cross walls (Sahm 1988:2). It is illustrated in Figure 3.4. The tomb is badly disturbed, with architectural features and archaeological material preserved more fully on its eastern side. The tomb was robbed in antiquity, and evidence exists to suggest that the robbery took place only a short time after the construction and use of the tomb (Sahm 1988:2), i.e. by the early second millennium BCE. The tomb is highly disturbed and only minor areas of articulation are visible in the excavated skeletal material, which is also largely burnt (Blau and Beech, 1999:34). Physical anthropological examination indicates that a minimum of 438 individuals were buried in the tomb (Blau 2001:Table 1). Pottery vessels and metal objects were found in small numbers inside the tomb, in addition to numerous beads made of "steatite paste" and an etched carnelian bead. A few examples of se'rie re'cente soft-stone were recovered from immediately outside the tomb, and it has been suggested that some of them may post-date the third millennium BCE (Sahm 1988:3). The excavated ceramic vessels were mostly fine wares and predominantly local black-on-red examples but there were also three black-on-gray Iranian vessels and one sherd of incised gray ware from Iran (Sahm 1988:Figure 10). Metal finds include one gold bead

and two silver beads, as well as a number of small fragments of copper-base objects such as rings and pins or awls. Additionally, a broken socketed spearhead was excavated from the tomb deposit (Sahm 1988:Figure 11.3). The majority of the excavated material from Unarl suggests a date in the middle Umm al-Nar Period, ca. 2400-2200 BCE (Blau 2001:Table l ) , however the possibility of re-use in the late third or early second millennium cannot be excluded because of the presence of the socketed copper-base spearhead. The analyzed copper-base objects from Unarl are shown in Table 3.2 and examples are illustrated in Figure 3.5. In addition to the rings and pinslawls mentioned by Sahm, there are a number of thin, flat metal fragments from the tomb that may once have belonged to vessels or blades, and some curved fragments that Table 3.1 Objects from AI Sufouh analyzed by PlXE Context

Object

ALSUFOOH

Reg. No.

Tomb I: chambers 4,6

blade fragment

ALSUFOU

Tomb I: chambers 4,6

blade fragment

ASI-l

Tomb I: chambers 4,6

flat fragment

ASI-2

Tomb I: chambers 4,6

thick flat fragment

ASI-3

Tomb I: chambers 4,6

thin flat fragment

ASI-4

Tomb I: chambers 4,6

blade edge fragment

ASI-5

Tomb I: chambers 4,6

blade edge fragment

ASTOMBI a

Tomb I: chambers 4,6

blade fragment

ASTOMBI b

Tomb I: chambers 4,6

blade edge fragment

ASTOMBI c

Tomb 1:chambers 4,6

blade edge fragment

ASTOMB1d

Tomb I: chambers 4,6

thin flat fragment

ASTOMBI e

Tomb I: chambers 4,6

thin flat fragment

ASTOMBI f

Tomb I: chambers 4,6

thin flat fragment

ASTOMBI g

Tomb I: chambers 4,6

thick flat fragment

ASTOMBI h

Tomb I: chambers 4,6

thin flat fragment

M10-15

Tomb I: chambers 4,6

blade edge fragment

M10-31

Tomb I: chambers 4,6

rivet

M 10-34

Tomb I: chambers 4,6

dagger-riveted-long

M10-36

Tomb I: chambers 4,6

dagger-riveted-tang

M10-30

Tomb I: chambers 4,6

blade edge fragment

M10-41

Tomb I: chambers 4,6

dagger-tanged

M 10-43

Tomb 1:chambers 4,6

thin flat fragment

Copper-base artifacts from the Umm al-Nar Period tomb at AI Sufouh that are compositionally analyzed in this study.

Analyzed Artifacts: Contexts and Chronology

61

gQm

-p-

pJm.*

...-. '

. ..

. :v

Figure 3.3 A selection of fragments of copper-base objects from AI Sufouh analyzed in this study.Top row, left to right: ASI-5, ASI-4, M10-30, ASTOMB1 b, ASTOMB1c, ASTOMB1a. Middle row, left to right: ASTOMBlf, ASI-3, ASTOMB1d, ASTOMB1h, ASI-2, M10-42 (not analyzed).Bottom row, left to right: ASI-1, M10-43, ASTOMBl g, M10-31.

Figure 3.4The Unarl Umm al-Nar Period tomb (photo courtesy and copyright C.Velde).

62

Early Metallurgy of the Persian Gulf

may have been tubes or spouts. Although the copperbase objects remaining at Unarl are obviously only a small fraction of those which may once have been interred there, enough typological diversity exists to suggest that the compositional variability of the original deposit may also be reasonably well represented.

Unar2 The Umm al-Nar tomb Unar2 (see Figure 3.6) is located in the Shihu village of Shimal North, in the Emirate of Ras al-Khaimah, about 200 m south of the Unarl tomb described in the previous section (Blau and Beech 1999:34). The site was excavated over two seasons in 1997 and 1998, revealing a round, stone-built tomb with a diameter of approximately 14.5 m, making Unar2 the largest Umm al-Nar funerary structure yet discovered in southeastern Arabia. The interior of the tomb was divided into 1 2 chambers forming three separate units, possibly related to familylkinship groups (Velde 1999; see Blau 2001:Figure 3; Blau and Beech 1999:Figure 2), although the original architectural features of the tomb have been disturbed by tomb-robbing. Evidence exists to suggest that the tomb may originally have stood to a height of about three meters and included an upper story (Velde 1999). The tomb remains partially unpublished, although notes on the ceramic assemblage (Carter 2002) and skeletal remains (Blau 2001; Blau and Beech 1999) have appeared, and a brief site summary (Velde 1999) and physical anthropology report (Blau 1999) have been posted on the National Museum of Ras al-Khaimah website. Anthropological studies by S. Blau (2001,1999) indicate that at least 43 1individuals were interred in the Unar2 tomb. Articulated skeletons were rare, being found only in chambers D and G, and more than 90 percent of the disarticulated bone was burnt. As for most Umm al-Nar tomb skeletal assemblages, the bones were predominantly of adults, although fetal, infant, child and adolescent bones were found in each chamber (Blau 1999).It is suggested by Velde (1999)that bodies may first have been interred on the chamber floors until no space remained in the tomb, at which point the bones were removed for cremation and later deposited in the upper story of the tomb (see also Carter 20025). The period of use of the tomb is regarded as lasting more than 100 years (Velde 1999).

Table 3.2 Objects from Unarl analyzed by PlXE Reg. No.

Context

L11D-PIN

Unarl Tomb

pinlawl fragment

L14N-PIN

Unarl Tomb

pinlawl fragment

LlSRlNG

Unarl Tomb

ring fragment

M10-7

Unarl Tomb

flat fragment

M10-12

Unarl Tomb

thin flat fragment

M10-13V

Unarl Tomb

thin flat fragment

M10-1

Unarl Tomb

tubelspout fragment

M10-17

Unarl Tomb

ring fragment

M10-18

Unarl Tomb

ring fragment

M10-19

Unarl Tomb

ring fragment

M10-20V

Unarl Tomb

thin flat fragment

Object

M10-21V

Unarl Tomb

tubelvessel fragment

M10-22R

Unarl Tomb

ring fragment

M10-35

Unarl Tomb

thin flat fragment

M10-38

Unarl Tomb

tubelspout fragment

M10-39

Unarl Tomb

thin flat fragment

M10-44

Unarl Tomb

pinlawl fragment

M10-46

Unarl Tomb

ring fragment

Copper-base artifacts from the Unarl Umm al-Nar Period tomb at Shimal that are compositionally analyzed in this study.

Figure 3.5 A selection of fragments of copper-base objects from Unarl analyzed in this study.Top row, left to right: LISRING, M10-22R, M10-46, M10-18. Bottom row, left to right: M10-44, L14N-PIN, L1 1DPIN, M10-16, M10-12.

Analyzed Artifacts: Contexts and Chronology

63

Figure 3.6 The Unar2 tomb after excavation, showing chamber designations, viewed from the north (photo courtesty of D. Kennet).

Pottery and stone vessels, metal objects and jewelry remained in the tomb even after robbing, with the pottery indicating contacts with Mesopotamia, Bahrain, Iran and the Indus Valley (Carter 2002; Velde 1999). Typical black-on-red indigenous funerary vessels comprise more than 80 percent of the ceramic assemblage, while imported Iranian black-on-gray and incised graywares represent just over 10 percent of the excavated pottery (Carter 2002:7-10). A small number of sherds of socalled "Kaftari ware" from Fars province in Iran has been recovered, and Barbar, Mesopotamian and Indus wares are similarly rare (Carter 2002:9-10). Assessment of the material from the site was initially used to suggest a date of ca. 2300-2100 BCE (Blau and Beech 1999:34). However, ceramic parallels cited by Carter (2002:12-13) suggest a foundation date perhaps 50-100 years later than this, and abandonment some time in the last century of the third millennium BCE, i.e. a construction and use spanning ca. 2200-2000 BCE. Thus, although earlier reports had described the Unar2 tomb deposits as late Umm an-Nar but not in the terminal phase, the new ceramic studies and particularly the presence of a number of anomalous ceramic forms led Carter (2002:13) to suggest that use of Unar2 may have continued into the terminal Umm al-Nar Period. Carter (2002:6) also observes that approximately six percent of the analyzed ceramic assemblage from Unar2 consists of later intrusive material from the second millennium, Iron Age and more recent periods. The possi-

64

Early Metallurgy of the Persian Gulf

bility that any analyzed metal objects from Unar2 are intrusive is small, but should not be forgotten. The analyzed copper-base objects from Unar2 are listed in Table 3.3 and illustrated in Figure 3.7, and consist primarily of rings, pins or awls and thin flat fragments. These are, in general, the largest metal objects that remained in the tomb after it was plundered in antiquity. It is likely that a much larger and more typologically diverse group of copper-base objects was once buried within the tomb.

Tell Abraq The archaeological site of Tell Abraq is situated on the border of the Emirates of Sharjah and Umm al-Qaiwain, several kilometers south of the present shore of the Gulf. The site has been systematically excavated for five seasons, from 1989-1993 and in the winter of 1997-1998, following test excavations at the site by an Iraqi team in the 1970s (Potts 1990b). Material from the first four seasons of excavation has been published and discussed in a number of places (Potts 1990b, 1991, 1993a), and some material from the most recent excavation season is also published (Potts 1998, 2000, 2003b). Tell Abraq is one of the largest sites on the southern shores of the Gulf, and shows evidence for continuous occupation from ca. 2300-300 BCE (i.e. Umm alNar Period to Iron Age), with a later re-occupation in the Ed Dur period (Potts 1993a). The chronology of

occupation at Tell Abraq, particularly in the third millennium BCE, is well established by both stratigraphic and typological considerations and by radiocarbon determinations (Potts 1997a:Table 3; Potts and Weeks 1999). The earliest occupation at the site is represented by the construction of a large stone and mud brick tower, approximately 40 m in diameter, which stood approximately eight m above the surrounding ground surface (Potts 1993a:118). Such towers are typical of third millennium BCE settlements in southeastern Arabia (Potts 1997b:47), although the Tell Abraq tower is the largest known example of its type. Occupation of the tower continued in the second millennium BCE, and a settlement also spread out around the fortified structure in the form of palm-frond houses, known locally as barasti or 'arish (Potts 1991:36-42; King 1997:87). By the end of the second millennium, most of the large architectural structures at the site seem to have been covered by earth and archaeological deposits, forming a mound around which barasti occupation spread in the first millennium BCE (Potts 1993a:119). For most of the period of its occupation, Tell Abraq is likely to have been the largest settlement on the southern shores of the Gulf. The material remains recovered during excavation (Potts 1990b; 1991; 1993a), and the reconstructions of past subsistence practices (Willcox and Tengberg 1995), indicate that in most respects Tell Abraq fits comfortably within the spectrum of local Bronze and Iron Age societies. Towards the end of the third millennium BCE, an Umm al-Nar type tomb was constructed just 10 m to the west of the fortification tower at Tell Abraq (Potts 1993a). The circular tomb (see Figure 3.8) is built of rough stones with an external facing of finely fitted ashlar masonry. The tomb diameter is approximately six m, it has one internal wall that divides the tomb into eastern and western chambers, and survives to a height of 1.5 m in places. The tomb is unusual in southeastern Arabian archaeology as it has remained untouched by looters and largely undisturbed since its construction and use (although the northwest corner of the tomb was destroyed in antiquity by later construction activities). This is perhaps due to the fact that the tomb was covered already by settlement deposits as early as the first half of the second millennium BCE (Potts 1993a:119).

Table 3.3 Objects from Unar2 analyzed by PlXE Reg. No.

Context

Object

1005.40

NW quadrant

lump

1007.41

outside tomb

thin flat fragment

1007.42

outside tomb, west side

ring fragment

1012.52

SE quadrant

ring fragment

1014.1 58

SW quad, chamber JIK

ring fragment

1014.76

SW quad, chamber JIK

ring fragment

1015.1 44

chamber H

thin flat fragment

1015.95

NW quad, chamber H

thin flat fragment

1018-3.93

NE quad, chamber A

pinlawl fragment

1018-3.99

NE quad, chamber A

thin flat fragment

1019-3.1 04

NE quad, chamber A

pinlawl fragment

1019-3.105

NE quad, chamber C

thin flat fragment

1019-3.1 24

NE quad, chamber C

thin flat fragment

1019-3.59

NE quad, chamber C

thin flat fragment

1019-3.60

NE quad, chamber C

chisel (7)

1019-4.1 08

NE quad, chamber C

pinlawl fragment

1019-4.1 13

NE quad, chamber C

pinlawl (7)

1019-5.71

NE quad, chamber C

ring fragment

1022-2.1 60

NW quad, chamber H

pinlawl fragment

1023-2.1 10

no data

lump

1023-4.10

NE quad, chamber C

ring fragment

surf. 56

surface

pinlawl fragment

Copper-base artifacts from the Unar2 Umm al-Nar Period tomb at Shimal that are compositionally analyzed in this study.

The western chamber of the tomb was excavated in 1993, revealing the disarticulated remains of at least 119 individuals, including all age groups from fetal to very old (>S0 years old) adults (Blau 1996:151; cf. Potts 1993a:120-121, who suggests a MNI of 155). In addition to skeletal material, typical Umm al-Nar ceramic and soft-stone vessels were recovered from the western chamber, as well as copper and bronze objects (see Figure 3.9), carnelian and agate beads, linen (Reade and Potts 1993) and other items including an ivory comb likely to be of Bactrian origin (Potts 1993d). Preliminary typological comparisons suggested that the tomb deposits could be dated to the very end of the third millennium BCE, the local pottery in particular showing form and technical detail more common in Wadi Suq ceramics (Potts 1993a:120). Additionally, two radiocarbon dates

Analyzed Artifacts: Contexts and Chronology

65

Figure 3.7 A selection of fragments of copper-base objects from Unar2 analyzed in this study.Top row, left to right: 10194.108,1018-3.93,1019-3.104,1019-4.113,surf.56.Second row, left to right: 1014.76,1014.158,1012.52,1023-4.10,1019-5.71. Third row, left to right: 1019-3.60,1022-2.160,1015.95,1007.42,1005.40. Bottom row, left to right: 1023-2.110,101 9-3.59, lOO7.41,lOl 5.1 44,101 9-3.1 24.

66

Early Metallurgy of the Persian Gulf

from a charcoal deposit running directly beneath the tomb building surface show calibrated ranges in the last third of the third millennium BCE (samples K-5574 and K-5575, see Table 3.4 and Potts 1993a:Table l),providing a useful terminus post quem for the construction of the tomb. Due to a border dispute at the site, the eastern chamber of the Umm al-Nar tomb was not excavated until 1997-1998, and remains largely unpublished. As for the western chamber, large amounts of disarticulated and partially articulated skeletal material were recovered, and the MNI for the entire tomb is about 330 individuals (D. T. Potts, personal communication). The cultural material from the eastern chamber represents the kind of extremely rich assemblage that may have characterized many Umm al-Nar tombs prior to robbery. In addition to numerous examples of local Umm al-Nar ceramic and soft-stone vessels, pottery from Mesopotamia, Bahrain, southwest and southeast Iran was present in the tomb (Potts 1998:10, 28-29; Potts 2000:l l 6 ff.; Potts 2003a). Additional finds included: numerous copper-base objects; more than ten ivory combs with Indus and central Asian parallels (Potts 1998:28-29); at least four alabaster vessels (Potts 2000:125); gold, lapis lazuli and carnelian beads with parallels in the Indus Valley region; and gold and silver animal pendants (Potts 2000:24, 54; see also Potts 2003 b). A series of five radiocarbon dates were run on wood charcoal from various levels of the bone deposit in the eastern chamber, the results of which are published in Potts and Weeks (1999), listed in Table 3.4. They confirm the dating of the tomb to the final stages of the third millennium BCE, but show no stratigraphic dependence. In fact, the five dates from the eastern chamber are statistically identical at a 95 percent confidence level, and provide an average 2 0 calibrated range of 2200-2040 BCE (Potts and Weeks 1999). The analyzed metal objects from Tell Abraq are listed in Tables 3.4 and 3.5 and illustrated in Figures 3.10-3.16. A total of 21 copper-base samples were analyzed, representing 10 percent of the 202 copperbase objects recovered from the eastern tomb chamber. The analyzed samples show significant typological diversity, including rings, daggers, spearheads and thin

Figure 3.8 The Tell Abraq tomb after excavation, looking from the north (photo D. Potts).

Figure 3.9 Two copper-base rings from the Tell Abraq tomb, as excavated in position on disarticulated human phalanges (photo D. Potts).

flat fragments. The total assemblage of copper-base objects from the eastern chamber of the tomb includes 2 1 socketed spearheads similar to Wadi Suq types, 10 dagger blades of varying typology, and more than 120 finger rings, toe rings and earrings.

Analyzed Artifacts: Contexts and Chronology

67

Table 3.4

Table 3.5

AMS radiocarbon dates associated with the Tell Abraq Tomb Calibrated I4cAge BP Age BCE Sample Code Context (Raw) (2 o range)

Objects from the Tell Abraq Tomb analyzed by PlXE Reg. No.

Context

Object

east chamber: layer 1

fragment

burnt layer

east chamber: layer 2

dagger (tanged)

underlying tomb

east chamber: layer 2

ring

east chamber: layer 3

lump

burnt layer

east chamber: layer 1

dagger (rounded)

underlying tomb

east chamber: layer 4

blade fragment (riveted)

east chamber: layer 3

spearhead (tanged)

east chamber

east chamber: layer 5

dagger (tanged)

level 3(7.4-7.5 m)

east chamber: layer 4

dagger (tanged)

east chamber: layer 3

dagger (tanged)

east chamber: layer 3

ring (flat band)

east chamber level 4 (7.6-7.7 m)

east chamber: layer 4

ring (broad flat band)

east chamber: layer 6

dagger (tanged)

level 6 (7.8-7.9 m)

east chamber: layer 5

ring

east chamber: layer 5

ring fragment

east chamber

east chamber: layer 5

ring

level 6 (7.8-7.9 m)

east chamber: layer 5

ring

east chamber: layer 6

thin flat fragment

east chamber: layer 6

thin flat fragment

east chamber: layer 6

spearhead (socketed)

east chamber: layer 6

ring

east chamber

east chamber level 6 (7.87 m) AMS radiocarbon dates from the eastern chamber of the Umm alNar Period tomb at Tell Abraq. All dates are calibrated with CALlB 4.1.2 (Stuiver and Reimer 1993), using dataset 1 (decadal dataset t o 23,999 cal BP) and calculation method B (probabilities). Calibrated ranges have been rounded t o nearest 10 years.

68

Early Metallurgy of the Persian Gulf

Copper-base artifacts from the Umm al-Nar Period tomb at Tell Abraq that are compositionally analyzed in this study.

Figure 3.10 A selection of fragments of copper-base objects from Tell Abraq analyzed in this study. Top row, left t o rig ht:TA2094,TA2679,TA281 6,TA233g1TA2677. Middle row, left t o right:TA2440 (tip), TA291 8,TA243S1TA2678. Bottom row, left t o right:TA2733,TA2732,TAI 785,TA2135.

Analyzed Artifacts: Contexts and Chronology

69

Figure 3.1 1 Spearhead TA2183 from the Tell Abraq Urnm al-Nar Period tomb. Length ca. 26.7 cm.

Figure 3.12 Daggerlknife blade TA2268 from the Tell Abraq Urnm al-Nar Period tomb. Length ca. 27.2 cm.

Figure 3.1 3 Dagger/knife bladeTA2270 from the Tell Abraq Urnm al-Nar Period tomb.

Figure 3.1 4 Daggerlknife blade TA2315 from the Tell Abraq Urnm al-Nar Period tomb. Length = 23.2.cm.

Figure 3.1 5 Daggerlknife blade TA2440 from the Tell Abraq Urnm al-Nar Period tomb. Length ca. 19.5 cm.

Figure 3.1 6 Socketed spearhead TA2757 from the Tell Abraq Urnm al-Nar Period tomb. Length = 33.8 cm.

70

Early Metallurgy of the Persian Gulf

4

Results of Compositional Analyses

Introduction In this chapter, the results of the chemical analysis of 83 archaeological objects from A1 Sufouh, Unarl, Unar2, and Tell Abraq are presented and discussed. The data are the results of Proton-Induced X-ray Emission (PIXE) analyses conducted at the Australian Nuclear Science and Technology Organisation (ANSTO), Lucas Heights, New South Wales. The PIXE compositional data for all objects are presented in Tables 4.1-4.4, on a site-by-site basis. Details of the analytical techniques used in this volume, including sample preparation, instrumental settings, accuracy, precision and sensitivity can be found below or in Appendix One. A brief introduction to the analyses and a general description of data treatment and presentation is given below, following which the PIXE data are presented and discussed in a univariate manner element by element. Subsequently, relationships between elements and archaeological assemblages are investigated through bivariate and multivariate statistical techniques. Sensitivity, Precision, and Accuracy of the MXE Data PIXE data were collected and quantified for the elements silicon (Si),phosphorus (P),sulfur (S),chlorine (Cl),potassium (K), calcium (Ca),titanium (Ti),vanadium (V),manganese (Mn), chromium (Cr),iron (Fe), cobalt (CO),nickel (Ni),copper (Cu),zinc (Zn),arsenic (As),selenium (Se), bromine (Br), rubidium (Rb), strontium (Sr), silver (Ag),

tin (Sn), antimony (Sb), lead (Pb), gold (Au) and bismuth (Bi). All measured phosphorus, rubidium, gold and bismuth concentrations were below levels required for acceptable analytical precision, and are not discussed further in this section. All chromium determinations have been disregarded due to the possibility of spurious Cr peaks in some samples due to occasional problems with beam alignment (see Appendix One (Section 1.1.4). All data have been normalized following procedure outlined in Appendix One (Section 1.2.1). PIXE data are presented as either percentage or parts per million (ppm) values, depending upon their concentration in the object. The sensitivity of the PIXE technique is represented by a quantity known as the minimum detectable level (MDL). The MDL is the theoretical minimum amount of an element that can be discerned by the PIXE analytical technique. Factors governing the MDL are discussed in Appendix One. MDLs are important in understanding the precision of the compositional data generated by PIXE; the higher the concentration of a particular element above the MDL, the better the precision that can be associated with the measurement. Values below the MDL, although frequently produced by the quantification software, are highly unreliable and must be regarded as at best a rough guide to element concentration (personal communication, Dr. G. Bailey, ANSTO, 1997). Further, it can generally be taken that the calculated concentration of an individual element is relatively imprecise (220-40 percent) at levels of one to three times the MDL. At concentrations of more than five times the MDL, precision is better than f10 percent for most elements. In the statistical summaries presented below, data tables for individual elements include a footnote containing numerical values for the MDL for each sample. The MDL value presented for each element is the average of the large amount of raw MDL data collected during PIXE analyses. The overall accuracy of the PIXE system at ANSTO is approximately 210 percent (Dr. R. Siegele, ANSTO, personal communication). However, the corroded nature of the majority of analyzed samples renders the quest for absolute accuracy of measurement somewhat futile. It must be accepted that the composition of the archaeological samples may have changed significantly from that of the objects during their original period of use (Scott 1991).

Table 4.1 Compositionaldata for AI Sufouh objects Lab Code

Object

ASI-l

flat fragment

ASI-2

thick flat fragment

ASI-3

thin flat fragment

ASI-4

blade edge

ASI-5

blade edge

M10-15

blade edge

M10-31

rivet

M10-34

dagger-riveted-long

M10-36

dagger-riveted-tang

M10-30

blade edge

M10-41

dagger-tanged

M10-43

thin flat fragment

ALSUFOOH

blade

ALSUFOU

blade

ASTOMBI a

blade fragment

ASTOMBI b

blade edge

ASTOMBI c

blade edge

ASTOMBI d

thin flat fragment

ASTOMBI e

thin flat fragment

ASTOMBI f

thin flat fragment

ASTOMBl g

thick flat fragment

ASTOMBl h

thin flat fraqment AVERAGE MDL

S

Fe

CO

Ni

Cu

Zn

As

(%)

(%)

(%)

(%)

(%)

(%)

(%)

0.10

0.007

0.01

0.04

0.007

0.012

0.008

Se

Ag

( P P ~ ) (pp4

50

240

Sb

Sn

(PP~)

(96)

(pprn)

0.13

135

700

Pb

PIXE compositional data for copper-baseobjects from AI Sufouh. Note: blank cells indicate concentrations below the MDL; nm = not measured.

Presentation of the PIXE Data As noted above, the normalized PIXE data is presented in Tables 4.1-4.4. However, the discussion presented below employs a number of statistical summaries of the PIXE concentration data. When the data for individual elements are discussed, they are summarized statistically (Table 4.5) by giving the median and the tenth-ninetieth percentile range. Furthermore, the statistical summaries for each site are presented in three broad categories: a summary for all objects from the site, a summary for the subset of tin-bronzes (i.e. samples containing more than two percent tin), and a summary for the samples with less than two percent tin (designated "copper"). Details regarding the selection and application of these statistical analyses are given in Appendix One (Section 1.2.2).

72

Early Metallurgy of the Persian Gulf

In addition, summaries of previous analyses are presented for most elements (e.g.Table 4.6). These summaries allow the composition of the Umm al-Nar Period material analyzed in this study to be compared with the contemporary and later objects from southeastern Arabia analyzed as a part of othek analytical programs. Summaries of previous analyses are provided for the following categories: Umm al-Nar Period objects (2700-2000 BCE); Umm al-Nar Period ingot and raw copper fragments (2700-2000 BCE); Wadi SuqILate Bronze Age objects (2000-1300 BCE); mixed Wadi SuqIIron Age tomb groups (2000-300 BCE); and Iron Age objects (1300-3 00 BCE). Geographic and bibliographic details of the previously collected data summarized in these tables is given in Appendix One (Section 1.2.3). Important information on arsenic, nickel and tin

Table 4.2 Compositional data for Unarl objects Lab Code

Object

M10-7

flat fragment

M10-12

thin flat fragment

M10-13V

thin flat fragment

M10-16

tube/spout

M10-1

ring

M10-18

ring

M10-19

ring

M10-2OV

thin flat fragment

M10-21V

tube/vessel

M10-22R

ring

M10-35

thin flat fragment

M10-38

tubelspout

M10-39

thin flat fragment

M10-44

pinlawl

M10-4

ring

L11D-PIN

pinlawl

L14N-PIN

pin/awl

LlSRlNG

S

Fe

CO

Ni

(%)

(%)

(%)

(%l

0.007

0.01

0.012

rinq AVERAGE MDL

0.10

0.008

0.007

50

240

700

0.13

135

PIXE compositional data for copper-base objects from Unarl. Note: blank cells indicate concentrations below the MDL.

concentrations in Bronze Age and Iron Age objects has also been presented in graphical form by Prange et al. (1999), and semi-quantitative compositional data exist for copper-base objects from the sites of Tell Abraq (Weeks 1997) and Umm an-Nar Island (Craddock 1981). Results of these studies are referred to in the text where relevant, but are not presented with the statistical summaries of previous analytical programs. In most cases, statistically summarized data distributions are accompanied by graphical presentation of the data to aid interpretation (e.g. Figure 4.1). Data are summarized graphically in the form of frequency histograms. The histograms are presented in either percentage terms or ppm on a logarithmic scale, with each order of magnitude divided into four geometric intervals. On the histograms, the bar delineated by crosshatching represents the number of objects in which the elemental concentration was below the MDL. Further details of the construction of these histograms are provided in Appendix One (Section 1.2.4).

Elemental Concentrations Sulfur (S) A summary of the PIXE sulfur measurements from this study is given in Table 4.5 and Figures 4.1-4.2. Ranges reported are tenth to ninetieth percentile values. As shown, sulfur concentrations are less than one percent in most of the samples. Seven of the 83 analyzed samples contain S concentrations of greater than one percent, with levels reaching as high as 5.5 percent in a spearhead from Tell Abraq (TA2183) and 3.7 percent in a riveted dagger from A1 Sufouh (M10-34). Relatively high sulfur concentrations appear in a thin flat fragment (TA2732,2.4 percent S) and an unidentified fragment (TA1785, 1.5 percent S) from Tell Abraq. Both Table 4.5 and Figure 4.2 indicate a significant difference in the sulfur content of copper objects and tin-bronzes, the latter containing lower median sulfur concentrations and a significantly smaller tenth to ninetieth percentile range. Further illustrating this point, only one analyzed tin-bronze, from Unar2, contains in excess of one percent sulfur (1015.144, 1.5 percent S).

Results of CompositionalAnalyses

73

Table 4.3 Compositional data for Unar2 objects S Lab Code

Object lump

(%)

Fe

CO

Ni

Cu

Zn

As

Se

(%)

(%)

(%)

(%l

(W

('W

(wm)

Ag

Sb

Sn

(pprn)

(PP~)

(%l

Pb (PP~)

0.25

thin flat fragment 0.22 ring ring ring

0.45

thin flat fragment ring thin flat fragment 1.49 pinlawl thin flat fragment 0.24 thin flat fragment chisel? ring

0.22

ring

0.53

pinlawl

0.20

thin flat fragment thin flat fragment pinlawl

0.09

pinlawl pinlawl

0.37

lump pinlawl

0.23

AVERAGE MDL

0.10

PIXE compositional data for copper-base objects from Unar2. Note: blank cells indicate concentrations below the MDL.

No consistent chronological variation in sulfur concentrations can be seen, although variation by site is clear. Figure 4.1 documents objects from Unar2 that have lower median S concentrations and ranges than material from the other Umm al-Nar Period tomb assemblages. In particular, half of the analyzed objects from Unar2 contain S concentrations of less than the minimum detectable level (ca. 0.10 percent) of the PIXE technique. Furthermore, only one object from Unar2, the previously mentioned tin-bronze (1015.144) contains more than approximately 0.5 percent S. Only a small number of previous analyses of S concentrations in archaeological copper-base objects are published, and these are summarized in Table 4.6. Fully published analyses from the Umm and-Nar and Wadi Suq Periods are all of copper objects, and have a much lower median S concentration but a similar range of up to

74

Early Metallurgy of the Persian Gulf

ca. 0.8 percent. Contemporary samples analyzed in a previous study of the metallurgy at Tell Abraq (Weeks 1997: Table 14) have median S concentrations of ca. 0.1-0.2 percent, close to the detection limit of the EDS analytical technique used, and a maximum value of ca. one percent S. Analyses of Bronze Age copper ingots and raw copper fragments by Hauptmann (1985:Table 21) show high S concentrations of up to approximately five percent, with median concentrations of approximately one percent S. Analyses of the same samples are given in Hauptmann et al. (1988), but do not show S determinations. Similarly, high sulfur concentrations of up to six percent were found in the copper ingots from the slightly later Saar settlement on Bahrain (Weeks, forthcoming a). The high sulfur concentrations in these semi-processed objects suggest a relationship between S content and the degree of metal refining which will be addressed in the following chapter.

Table 4.4 Compositionaldata for Tell Abraq objects Lab Code

Object

S

Fe

CO

Ni

Cu

Zn

As

(%)

(%)

(%)

(%l

('W

(W

(W

0.007

0.01

0.04

0.007

fragment

1.46

dagger-tanged

0.1 2

ring

0.3 1

lump

0.91

dagger-rounded

0.23

Se (ppm)

Ag (PP~)

Sn

(%l

Pb (PP~)

blade fragment (rivets) 0.31 spearhead-tanged dagger-tanged dagger-tanged dagger-tanged ring-flat ring-broad flat dagger-tanged ring ring fragment ring ring thin flat fragment thin flat fragment spear-socketed ring

0.02

AVERAGE MDL

0.10

58.7 0.012

0.008

0.40

PIXE compositional data for copper-base objects from Tell Abraq. Note: blank cells indicate concentrations below the MDL. Table 4.5 Sulfur in Umm al-Nar Period objects analyzed in this study Median

Median

Sulfur (%)

(all)

(copper)

Median

AI Sufouh

0.35

0.36

Unarl

0.30

0.30

0.29

0.15-0.61

0.1 6-0.58

0.1 2-0.72

Unar2