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BEIhEft 26

Archaeometallurgy in Europe III

Andreas hauptmanndiana modarressi-tehrani

BEIhEft26

Archaeometallurgy in Europe III

EditorsAndreas HauptmannDiana Modarressi-Tehrani

Bochum 2015

Archaeometallurgy in Europe IIIProceedings of the 3rd International ConferenceDeutsches Bergbau-Museum Bochum

June 29 – July 1, 2011

DER ANSCHNITT

Herausgeber: Vereinigung der Freunde von Kunst und Kultur im Bergbau e.V.

Vorsitzender des Vorstands: Prof. Dr. Karl Friedrich Jakob

Vorsitzender des Beirats: Bergassessor Dipl.-Kfm. Dr.-Ing. E.h. Achim Middelschulte

Geschäftsführer: Museumsdirektor Prof. Dr. rer. nat. Stefan Brüggerhoff

Schriftleitung: Dr. phil. Andreas Bingener M.A.

Editorial Board: Prof. Dr. Stefan Brüggerhoff, Dr. Lars Bluma, Dr. Michael Farrenkopf, Prof. Dr. Rainer Slotta, Dr. Thomas Stölllner

Wissenschaftlicher Beirat: Prof. Dr. Jana Gerslová, Ostrava; Prof. Dr. Karl-Heinz Ludwig, Bremen; Prof. Dr. Thilo Rehren, London; Prof. Dr. Wolfhard Weber, Bochum

Anschrift der Geschäftsführung und der Schriftleitung:Deutsches Bergbau-Museum Am Bergbaumuseum 28 - D-44791 Bochum Telefon (02 34) 58 77-0Telefax (02 34) 58 77-111

Einzelheft 9,– €, Doppelheft 18,– €; Jahresabonnement (6 Hefte) 54,– €; kostenloser Bezug für die Mitglieder der Vereinigung (Jahres-Mitgliedsbeitrag 50,– €)

Montanhistorische Zeitschrift

Der ANSCHNITT. Beiheft 26

= Veröffentlichungen aus dem Deutschen Bergbau-Museum Bochum, Nr. 202

Cover

Domus Vettiorum / Casa dei Vettii, Pompeii (Campania, Italy, 63-79 BC), which was excavated in 1894. Section of a Pompeii-style scenic fresco showing Erotes and Psyches in a gold assay laboratory. In the left corner, scales for weighing gold are put on a table. Next to it, one of the Erotes is working with a small hammer on an anvil. On the right side, an assay furnace is shown. Ano-ther of the Erotes is holding a small crucible with pincers with the right hand while using a blowpipe with his left hand, supplying the fire with air. The large bellow for the assay furnace is driven by the third of the Erotes.

RedaktionDiana Modarressi-Tehrani, Andreas Hauptmann

LayoutRolf Krause

TitelgestaltungKarina Schwunk

DruckGrafisches Centrum Cuno GmbH & Co. KG

Bibliografische Informationen der Deutschen Bibliothek

Die Deutschen Bibliothek verzeichnet diese Publikation in der Deutschen Nationalbibliografie; detaillierte bibliografische Daten sind im Internet über http/dnd.ddb.de abrufbar.

ISBN 10: 3-937203-74-5ISBN 13: 978-3-937203-74-4

The conference Archaeometallurgy in Europe III was supported by

Keyence

Analyticon

MLS GmbH

Zeiss

Thermo Scientific

Springer Verlag Berlin Heidelberg New York

Archaeometallurgy in Europe III

Scientific Advisory BoardGilberto Artioli, Universitá di Padova, Italy

Roland Gauß, Fraunhofer-Institut für Silicatforschung, ISC, Alzenau

Alessandra Giumlia-Mair, Merano, Italy

Gert Goldenberg, University of Innsbruck, Austria

Sabine Klein, J.W. Goethe University of Frankfurt/Main, Germany

Marcos Martinon-Torres, University College London, United Kingdom

William O’Brien, University of Galway, Ireland

Vincent Serneels, University of Fribourg, Switzerland

Standing Committee Yannis Bassiakos, Athens, Greece

Alessandra Giumlia-Mair, Merano, Italy

Andreas Hauptmann, Bochum, Germany

Ivelin Kuleff, Sofia, Bulgaria

Susan LaNiece, London, United Kingdom

Ignacio Montero, Madrid, Spain

Local Organizing Committee Michael Bode

Andreas Hauptmann

Diana Modarressi-Tehrani

Michael Prange

Ünsal Yalçın

This volume comprises a range of articles, which were submitted and selected from all the presentations given on the International Conference ”Archaeometallurgy in Europe III”, held from the 29th of June to 1st of July 2011 at the Deutsches Bergbau-Museum Bochum, Germany.

The present volume is the third in the series “Archaeo-metallurgy in Europe” , capturing the spirit of the suc-cessful series of international conferences on this special theme of research. The first conference “Archaeometal-lurgy in Europe” had been organized by the Associazi-one Italiana di Metallurgia and took place in Milano, Italy, from the 24th to the 26th of September 2003. The second conference was held in Aquileia, Italy, from the 17th to the 21st of June 2007. It was also organized by the Associazione Italiana di Metallurgia.

The splendid idea to launch this conference series, a scientific series of meetings limited to the countries of Europe, came from the late Prof. Dr. Walter Nicodemi, formerly President of the Assoziazione Metallurgia di Italia. Thanks to the efforts of Dr. Alessandra Giumlia-Mair, Merano, these conferences have developed into increasingly productive events with a high scholarly qua-lity. Since then three conferences have taken place and the fourth meeting is at an advanced stage of prepara-tion and will take place in Madrid, Spain, from the 1st to the 3rd June 2015.

The title of the conference series covers a research field which is a distinctive part of archaeometry, and which so far was usually included as one of the topics in the program of the “International Symposium on Archaeo-metry” (ISA), organized every third year at different lo-cations in Europe and in the United States. However it is our opinion, that in the last decade archaeometallurgy has developed as a very important research field, and we are observing a large number of scholarly activities all over the world. We are convinced that such an im-portant topic needs to be organised and presented in conferences specifically dedicated to this field. Therefo-re the topic of this conference is the history of metals and metallurgy primarily in Europe, but it also includes other regions of the Old World.

The future prospects of the conference series are pro-mising, especially because “Archaeometallurgy in Euro-pe” constitutes an extremely useful broadening and a regional counterpoint to the well-established and suc-cessful conference series “The Beginnings of the Use of Metals and Alloys” (BUMA), which was launched in

1981 by Professors Tsun Ko, Beijing, China, and Robert Maddin, then Philadelphia, USA. The focus of the eight BUMA conferences held so far (the last one was held in Nara, Japan, in 2013) lays on the development of metallurgy in South-East Asia and the Pacific Rim. We firmly belief that the two conferences complement each other very effectively and should therefore continue to exist side by side.

With this special volume of Der Anschnitt, we are de-lighted to publish a selection of the lectures presented at the conference at the Deutsches Bergbau-Museum Bochum in 2011. Many of the authors contributed with very instructive and informative papers, which finally resulted in this volume.

We are very much obliged to all these authors who, with patience and persistence, cooperated with us and helped to shape this volume. We would also like to thank the reviewers who decisively contributed in the improvement of the scientific level of this volume.

Our thanks go first to all those colleagues and friends who helped to organize the conference in 2011. The former director of the Deutsches Bergbau-Museum, Prof. Dr. Rainer Slotta, and the present director, Prof. Dr. Ste-fan Brüggerhoff encouraged and promoted our efforts to organize this scholarly meeting. Dr. Michael Bode, Dr. Michael Prange, and Prof. Dr. Ünsal Yalçın supported the conference planning and realization in every aspect. Many colleagues of the staff of the Deutsches Berg-bau-Museum, and many of the students working in our research laboratory offered their assistance and help.

Finally, our thanks go to Mrs. Karina Schwunk and Mrs. Angelika Wiebe-Friedrich who performed the editorial work, design, and layout for this volume.

Andreas HauptmannDiana Modarressi-Tehrani

Contemporaneously to the conference in 2011 a volume with abstracts on every lecture given and every poster presented was published:

2011 HAUPTMANN, Andreas, MODARRESSI-TEH- RANI, Diana & PRANGE, Michael (eds.), Archaeometallurgy in Europe III. Abstracts. METALLA, Sonderheft 4, 2011.

Editorial

Table of contents

Early mining and metallurgical innovation stages in Europe

Hans Anderssson Iron – a driving force in early urbanisation 13

Florence Cattin, Matthias B. Merkl, Christian Strahm & Igor Maria Villa Elemental and lead isotopic data of copper finds from the Singen cemetery, Germany – a methodological approach of investigating Early Bronze Age networks 19

Guntram Gassmann, Sabine Klein & Gabriele Körlin The Roman mines near Ulpiana, Kosovo 33

Marc PearceThe spread of early copper mining and metallurgy in Europe: an assessment of the diffusionist modelA key-note lecture 45

Ignacio Soriano The earliest metallurgy in the north-eastern Iberian Peninsula: origin, use and socioeconomic implications 55

Thomas Stöllner Humans approach to resources: Old World mining between technological innovations, social change and economical structures. A key-note lecture 63

Simon Timberlake, Tim Mighalll & Thomas Kidd Newresearch into Roman metal mining in Britain 83

Regional studies in Europe and beyond

Lucile Beck, Elise Alloin, Anne Michelin, Florian Téreygeol, Claire Berthier, Dominique Robcis, Thierry Borel & Ulrich Klein Counterfeit coinage of the Holy Roman Empire in the 16th century: silvering process and archaeometallurgical replications 97

Maryse Blet-Lemarquand, Arnaud Suspène & Michel Amandry Augustus’ gold coinage: investigating mints and provenance through trace element concentrations 107

Velislav Bonev, Boika Zlateva & Ivelin Kuleff Chemical composition of fibulae from the Iron Age in Thrace (Bulgaria) 115

Carlo Bottaini, Claudio Giardino, Giovanni Paternoster The Final Bronze Age hoard from Solveira (northern Portugal): a multi-disciplinary approach 125

Jennifer GarnerBronze Age tin mines in central Asia 135

Alessandra Giumlia-Mair, Susan C. Ferrence & Philip P. Betancourt Metallurgy of the copper-based objects from Gournia, east Crete 145

Elisa M. GrassiRoman metalworking in northern Italy between archaeology and archaeometry: two case studies 155

Babara Horejs & Mathias MehoferEarly Bronze Age metal workshops at Çukuriçi HöyükProduction of arsenical copper at the beginning of the 3rd millennium BC 165

Rüdiger KrauseNew horizons: archaeometallurgy in eastern Europe and beyondA key-note lecture 177

Janet LangThe Anglo-Saxon cemetery at Dover Buckland, Kent, UK and the technology of some of the iron artefacts 185

Lene MelheimLate Bronze Age axe traffic from Volga-Kama to Scandinavia? 193

Alicia Perea, Patricia Fernández-Esquivel, Salvador Rovira-Llorens, José Luís Ruvalcaba-Sil, Ana Verde, Oscar García-Vuelta & Fabián Cuesta-Gómez Prehistoric gold metallurgy: the Arqeomeb research project 203

Irina Ravich & Mikhail TreisterThe mirrors of the early nomads of the foothills of south Urals: a complex archaeo-technological study 211

Irina Segal, Miryam Bar-Matthews, Alan Matthews, Yehudit Harlavan & Dan AsaelProvenance of ancient metallurgical artifacts: implications of new Pb isotope data from Timna ores 221

Béla Török, Árpád Kovács & Zsolt GallinaIron metallurgy of the Pannonian Avars of the 7th - 9th century based on excavations and material examinations 229

Frank Willer, Roland Schwab & Kati BottLarge Roman Bronze statues from the UNESCO World Heritage Limes 239

Vladimir I. Zavyalov & Nataliya N. TerekhovaThree-fold welding technology in the blacksmith’s craft of Medieval Rus’ (concerning Scandinavian innovations) 247

Reconstructing ancient technologies

David Bourgarit & Nicolas ThomasAncient brasses: misconceptions and new insights 255

Vagn F. BuchwaldOn the characterization of slags and ancient iron artefacts applying the slag-analytical method 263

Joseph Gauthier, Pierre Fluck, Alessandre Disser & Carmela ChateauThe Alsatian Altenberg: a seven-hundred-year laboratory for silver metallurgy 271

Anno Hein, Ioannis Karatasios, Noémi S. Müller & Vassilis KilikoglouMaterial properties of pyrotechnical ceramics used in the Bronze Age Aegean and implications on metallurgical technologies 279

Silviya Ivanova, Veselina Rangelova, Deyan Lesigyarski & Ivelin KuleffObservations on the technology of Bronze Age copper and copper alloy finds from Bulgaria 287

David KillickArchaeometallurgy as archaeologyA key-note lecture 295

Steffen Kraus, Christian Schröder, Susanne Klemm & Ernst PernickaArchaeometallurgical studies on the slags of the Middle Bronze Age copper smelting site S1, Styria, Austria 301

Matthias Krismer, Gert Goldenberg & Peter TropperMineralogical-petrological investigations of metallurgical slags from the Late Bronze Age fahlore-smelting site Mauken (Tyrol, Austria) 309

Matthias B. MerklSome thoughts on the interpretation of the elemental composition of Chalcolithic copper finds from central Europe 319

Nerantzis NerantzisExperimental simulation study of prehistoric bronze working: testing the effects of work-hardening on replicated alloys 329

Barbara S. OttawayExperiments in archaeometallurgy A key-note address 337

Alessandro PaciniThe Lombard fibula of the Arcisa: a substitution? 347

Salvador Rovira, Martina Renzi, Auxilio Moreno & Francisco ContrerasCopper slags and crucibles of copper metallurgy in the Middle Bronze Age site (El Argar Culture) of Peñalosa (Baños de la Encina, Jaen, Spain) 355

Sana Shilstein & Sariel ShalevComparison of compositional variations in modern European bronze coins with variations in some ancient coins 363

Elena Silvestri, Paolo Bellintani, Franco Nicolis, Michele Bassetti, Siria Biagioni, Nicola Cappellozza, Nicola Degasperi, Marco Marchesini, Nicoletta Martinelli, Silvia Marvelli & Olivia Pignatelli New excavations at smelting sites in Trentino, Italy: archaeological and archaeobotanical data 369

Maria A. Socratous, Vasiliki Kassianidou & Gaetano Di PasqualeAncient slag heaps in Cyprus: the contribution of charcoal analysis to the study of the ancient copper industry 377

New approaches, new technologies in archaeometallurgy

Gilberto Artioli, Matteo Parisatto & Ivana AngeliniHigh energy X-ray tomography of Bronze Age copper ingots 387

Elisa Barzagli, Francesco Grazzi, Francesco Civita, Antonella Scherillo, Alessio Fossati & Marco ZoppiCharacterization of ancient Japanese sword hand guards through time-of-flight neutron diffraction and scanning electron microscopy 391

The authors 401

287

Summary

This paper examines the methods of production of a group of copper and copper alloy artefacts during the Bronze Age on the territory of North-East Bulgaria. It compares the manufacturing techniques of various finds characteristic for specific periods of time. Some of the finds are typologically influenced by the metal production of the neighbouring territories and others reflect the spe-cifics of local metallurgy. The chemical contents of the objects have been determined using ICP-AES. The mi-crostructures of the samples have been examined by optical microscopy and scanning electron microscopy. The results of the analyses have been subject to ar-chaeological interpretation in an attempt of clarifying some aspects of Bronze Age metallurgy on the territory of present Bulgaria.

Introduction

The only technological study of Bronze Age (BA) finds from Bulgaria has been carried out by E. Chernykh, N. Ryndina and L. Orlovskaya in the late 1970’s (Chernykh 1978), as a part of a project examining metal finds dat-ing from the Chalcolithic and Bronze Ages. Only six objects from the Early Bronze Age (EBA) and one from the Late Bronze Age (LBA) have been included in the metallographic research. No general conclusions have been drawn due to the few finds examined. For that reason a broader metallographic study was necessary to explore the methods of processing copper and its alloys during the Bronze Age.

This study is an attempt to identify the production tech-nology of a group of copper and copper alloy Bronze Age finds from Bulgaria. Various kinds of artefacts have been examined – tools, weapons and ingots. All the specimens are sporadical finds from North-East Bulgar-ia. The special feature of the artefacts is that they reflect cultural connections in many directions and also the traditions of local metallurgy. The aim of this research is to compare the manufacturing process of metal arti-

cles, typical for different chronological periods and cul-tural groups, by applying modern analytical instruments. It is a project exploring whether the copper alloy prepared for the production of different kinds of artefacts varies according to their function.

Archaeological material

This investigation presents the results of the chemical composition and microstructural studies of samples of sixteen archaeological finds (flat axe, adze, three awls, two oxhide ingots, five sickles, a socket axe (celt), two daggers and a knife) (Ivanova 2013).

The flat axe (Fig. 1. 1) and adze (Fig. 1. 2) are fragmen-tary and they could not be typologically discriminated. Two of the awls (Figs. 1. 4-5) are of a type with rectan-gular cross section and a narrowing, after a small en-largement, at the back parts (Panajotov 1978: 222). The awls and flat axes/adzes show genetic connections of the metal types from Bulgaria with those from the Ae-gean. These instruments are typical for the Early and Middle Bronze Age and are still present in the LBA (Chernykh 1978).

Observations on the technology of Bronze Age copper and copper alloy finds from Bulgaria

Silviya Ivanova, Veselina Rangelova, Deyan Lesigyarski & Ivelin Kuleff

Fig. 1: Metal finds from Northeast Bulgaria with Aegean influenc-es. A piece of axe (863.CF); A piece of adze (862.CF); Awls (864-866.CF).

Silviya Ivanova, Veselina Rangelova, Deyan Lesigyarski & Ivelin Kuleff

288

The oxhide ingots (Fig. 2) belong to type 2a after Buch-holz, and are dated between the 14th and the end of the 12th century BC. One of the items bears a composite mark, identified as symbol in the Eastern Mediterranean scripts (Leshtakov 2007: 449-452).

Copper oxhide ingots are found all over the Mediterra-nean. They are one of the principal forms in which cop-per was distributed by sea routes around the Mediter-ranean in the LBA (Gale & Stos-Gale 1999, 267). There is significant evidence for the fact that transportation of metal in the Eastern Balkans was carried out on river and land routes (Leshtakov 2007, 455).

The sickles (Figs. 3. 1-5) are of the Lower Danubian type Dichevo. The type is characteristic for metal hoards of the 13th century BC in North-East Bulgaria and Ro-manian Dobrudzha (Dergachev 2011: 184, 195).

The fragment of small socket axe (Fig. 3. 6) belongs to a celt with rarely encountered shape. The production of that kind of axes is connected with the end of 11th – 9th centu-ry BC in North-East Bulgaria (Dergachev 2011: 143-144).

The two fragmented daggers (Figs. 3. 7-8) find their parallels in the 14th – 13th century BC among the metal artefacts of the Northern Pontic cultures (Kloćko 1995: 124, 130).

The piece of knife (Fig. 3. 9) is of а type with a tang and no widening at the back part. That kind of knives has been found in LBA contexts in Bulgaria. In the Middle Danube and the Eastern Alpine regions similar knives were used until 9th century BC (Chernykh 1978: 236).

Methods of analyses

The production technology of the archaeological finds has been identified using metallographic methods. Stud-ies have been carried out using reflected light micro-scope - ОLYMPUS GX 51 with a Colour View Camera and scanning electron microscope in combination with focused ion beam - SEM/FIB LYRA I XMU, TESCAN with EDX detector - Quantax 200, BRUKER. Polished metal surfaces have been etched with chemical reagents to reveal their structure. The solutions used were aque-ous or alcoholic ferric chloride (FeCl3), potassium di-chromate (K2Cr2O7), and for some of the samples the solution of ammonium hydroxide (NH4OH) and hydrogen peroxide (H2O2).

The chemical composition (As, Cu, Fe, Mn, Ni, P, Pb, Sb, Se, Sn, and Zn) of the artefacts has been determined by inductively coupled plasma atomic emission spec-troscopy (ICP-AES – Perkin Elmer Optima 7000 DV). Certified reference materials BAM 211, BAM 227 are used to calibrate the instrument.

Unfortunately, there was no possibility to perform lead-isotope analysis of the artefacts because of the lack of such equipment in Bulgaria. Lead-isotope analysis will be performed in a future research project.

Results and discussion

Elemental composition

The results of the ICP-AES analysis of the examined finds are presented in Table 1.

The oxhide ingots have been analyzed using ICP-AES but also using INAA and XRF in a previous exploratory study carried out by I. Iliev (Iliev 2006, 90, 94). The ingots (834.VAR; 836.VAR) are made of copper. The relatively high concentrations of impurities (As, Co, Fe, Ni, Pb) determined by INAA and XRF lead to the conclusion that

Fig. 2: Oxhide ingots found between the villages of Kameno and Pobit kamak, Northeast Bulgaria (834, 836.VAR).

Fig. 3: LBA bronze finds from Northeast Bulgaria. Fragments of sickles (854-0858.CF); A fragment of socket axe (861.CF); Two pieces of daggers (868.CF, 869.CF); A piece of knife (859.CF).

Observations on the technology of Bronze Age copper and copper alloy finds from Bulgaria

289

the ingots have been made of unrefined metal, melted and refined subsequently. The high concentrations of iron, as well as nickel and cobalt are indicative for the use of low copper ore and high reducing conditions of smelting at high temperature (Craddock & Meeks 1987; Ivanova 2013: 250).

The chemical composition of the two oxhide ingots is fundamentally close to the oxhide ingots from the Ulu Burun shipwreck (see Table 1 and Hauptmann et al. 2002, 13). The results of the analyses of oxhide ingots from Greece (see, e. g., Mangou & Ioannou 2000: 207-217) are also similar to those obtained for the ingots from North-East Bulgaria (see Table 1). Given these comparative analyses, it can be stated that the examined oxhide ingots do not posses any peculiarities in their chemical contents. Nevertheless, there is a hypothesis that an iron slag was added in the copper melt during the production of the two oxhide ingots from North-East Bulgaria with the aim of increasing the weight of the final product (Dimitrov, pers. communication 2010).

Data obtained by ICP-AES analysis of all the other ar-tefacts, except the adze (862.CF) and one of the awls (864.CF), indicate that they have been made of tin bronze.

The concentrations of copper in bronze are between 86.6 % and 94.8 %. The concentrations of tin are in the interval between 2.4 % and 11.4 % and are common for bronze objects. At those levels of tin, the hardness and tensile strength of the metal enhance (see, e. g., Lechtman 1996, 488). The concentrations of lead and nickel in the samples might be a result of contaminations of the ore used by the ancient masters. These elements contents are respectively between less than 0,001 % and 1.6 % (Pb), and less than 0.001 % and 2.3 % (Ni). The presence of some other trace elements - manga-nese, selenium, iron and zinc in the alloy also reflects the contents of the ore sources. The content of arsenic in a sample of a sickle (857.CF) is 2.2 %. The constit-uent could be deliberately added to harden copper as the concentration of tin is only 4.9 %. More reliable pos-sibility is that the artefact was produced by recycled metals (among which arsenical coppers) which is a com-mon practice in the LBA. The concentrations of arsenic in the rest of the samples are within its expected bound-aries in bronze.

The presented analytical results of the ICP-AES exam-ination of the bronze finds are very similar to those ob-tained by E. Chernykh (Chernykh 1978). The same can be said for the results of the analyses of bronze objects

Artefact Date Lab.code Cu Sn Zn Ni Pb Fe As Sb P Se Mn

Adze EBA 862.CF 95.96 0.04 0.25 0.06 0.3 0.32 3.59 0.02 0.001 0.003 0.004

Axe MBA 863.CF 91.73 2.36 0.99 2.34 0.11 < 0.001 0.31 2.08 0.02 0.001 0.003

Oxhide ingot LBA 834.VAR 84.97 0.004 0.86 0.02 < 0.001 13.5 0.33 0.02 0.006 < 0.0001 0.06

Oxhide ingot LBA 836.VAR 97.47 0.001 0.99 0.04 < 0.001 1.11 0.33 0.02 0.007 0.0005 0.005

Sickle LBA 854.CF 89.04 9.02 0.91 0.16 0.21 0.21 0.05 0.08 0.42 0.02 0.001

Sickle LBA 855.CF 93.13 5.15 0.89 < 0.001 0.28 < 0.001 0.02 0.46 0.02 0.001 0.001

Sickle LBA 856.CF 92.54 4.34 0.95 0.5 < 0.001 1.08 0.11 0.76 0.02 0.003 0.001

Sickle LBA 857.CF 89.07 4.89 0.89 0.12 1.6 0.25 2.19 0.92 0.02 0.002 0.009

Sickle LBA 858.CF 94.75 4.31 0.91 0.004 0.03 < 0.001 0.007 0.41 0.02 0.001 0.001

Knife LBA 859.CF 90.49 7.29 0.94 0.008 0.33 0.02 0.02 0.84 0.02 0.001 0.001

Celt LBA 861.CF 87.8 10.12 0.91 0.14 0.33 0.22 0.009 0.42 0.02 0.001 0.001

Awl LBA 865.CF 92.69 6.61 0.93 0.02 0.06 0.02 0.06 0.006 0.007 0.21 0.02

Awl LBA 866.CF 86.64 11.37 0.86 0.25 0.02 0.04 0.77 0.02 0.006 0.0008 0.001

Dagger LBA 868.CF 90.28 7.24 1.86 0.02 0.19 0.22 0.09 0.08 0.007 0.0002 0.002

Dagger LBA 869.CF 90.84 7.36 0.9 0.47 0.03 < 0.001 0.06 0.24 0.02 0.001 0.002

Awl IA 864.CF 86.08 0.10 13.26 0.14 0.1 < 0.001 0.14 0.07 0.02 0.001 0.02

Table 1: Element concentrations in the analyzed samples of archaeological finds. Values are given in weight percent.

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290

dated to the Iron Age (see, e. g., Bonev et al. 2010; Iliev 2006; Lombardi 2009). We can not conclude from this exploratory study that bronze with specific element con-tents was used for the production of different kinds of artefacts. Undoubtedly, metal for the production of the finds under consideration has been derived from differ-ent sources. Such general inferences are not surprising in view of the fact that there are no copper ore deposits in North-East Bulgaria (Bogdanov 1987). Consequently, all artefacts from this region have been made of metals from different ore deposits and those metals were objects of trade.

The analysis of the flat adze (862.CF) shows that the find is made of an alloy of copper (95.96 %) and arsenic (3.6 %). The concentrations of some other elements in the sample are low (see Table 1). Arsenical copper may have been produced by smelting arsenic-rich copper ores, by co-smelting of arsenic sulphides (e.g. As4S6 – auripigment) with copper oxides, or by changing the smelting conditions (see e.g. Scott 1991: 83). There exists some linear correlation between the concentra-tions of arsenic and nickel and arsenic and iron in the sample. It could be accepted as evidence that arsenic was added as a mineral like nickeline (NiAs) or arseno-pyrite (FeAsS) (Ivanova 2013: 157-158).

A curious result is that one of the awls (864.CF) was discovered to be made of brass. It contains about 13.3 % of zinc but the concentration of some other elements is low - tin (0.1 %), nickel (0.1 %), arsenic (0.1 %). It is important to consider that the artefact is a sporadical find and its date is not precisely defined. It is highly probable that the find belongs to a period following the BA, since its distinctive shape has a continuous use and BA is too early date for the appearance of brass. The earliest possible time of production of the object is the time after the Late Iron Age (LIA).

The fact that quantitative trace element composition de-pends not only on the raw material but also on the smelt-ing, casting and working processes, should be also considered (see e.g. Merkl 2011: 78, 151). It provided the incentive for carrying out a microstructure analysis of the finished articles – in order to determine the arte-facts’ physical and mechanical properties.

Production technology

The metallographic examination revealed different kinds of microstructures of the samples which result from the various modes in which casting and working have been carried out. Furthermore, the same types of artefact have been made by different metalworking techniques.

Three of the sickles (855.CF, 857.CF and 858.CF) stud-ied show undistorted dendritic pattern (Fig. 4). The den-

drites are different in outline and size (fuzzy or rounded or quite sharp and well defined) depending on the nature of the alloy and the cooling conditions of the melt (see Scott 1991, 5). The microstructure of these samples is an indication that the articles were cast to shape in a mould without any further working. There are no mac-roscopic traces of sharpening or wear of the cutting edges of the finds so it may be supposed that they have never been used. It is obvious that one of the pieces is a bad casting (857.CF). Microscopic observations of the samples show the presence of numerous pores pointing out that there was no control over the temperatures of the mould and molten metal during pouring (see Valério et al. 2010: 1815). The above mentioned facts are evi-dence for the low quality of the produced objects.

Another sample (854.CF) also has dendritic structure but the dendrites near the cutting edge of the sickle seem heavily distorted (Fig. 5). This is a result of a short cold working after casting for hardening the edge of the implement. It is visible that the working part is well sharp-ened (probably also with a whetstone) and it bears trac-es of continuous use.

The microstructure of the last sickle (856.CF) shows equi-axed hexagonal grains with straight twin lines (Fig. 6). The object is made by casting followed by a cold work/anneal cycles with annealing as final operation. In some parts of the artefact (the cutting edge and the thick part) equi-axed hexagonal grains with slightly distorted twin lines and strain lines in the grains can be noticed. They are caused by final hammering for hardening and shaping the artefact. Stress corrosion cracking is also visible.

The production technology of the knife (859.CF) is rath-er similar. The microstructure also shows equi-axed hexagonal grains with straight twin lines. There are trac-

Fig. 4: Photomicrograph (x 100) of a section through a copper alloy sickle (855.CF) showing undistorted dendrites. The small grey inclusions are copper sulphide. Corrosion is visible.

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es of cold working as final operation and also intergran-ular and stress-cracking corrosion (Fig. 7). The cutting edge is extremely worn out.

The sample of the flat axe (863.CF) shows undistorted dendritic structure. The working part has been cold worked after casting to harden the tool.

The microstructures of the socket axe (861.CF), the adze (862.CF), the three awls (864.CF, 865.CF, 866.CF) and the daggers (868.CF, 869.CF) show equi-axed hexago-nal grains with straight twin lines. The production tech-nique was casting followed by a cycle or cycles of cold hammering and annealing (annealing as final operation). After the final annealing one of the awls (864.CF) was cold worked. The spherical pores in the microstructures of the samples of the socket axe and one of the daggers

(869.CF) are due to dissolved gases in the melt (Scott 1991: 6). The grain sizes of two of the awls (865.CF, 866.CF), at the same magnification, are different. They are small in the first sample because of the successive working and careful annealing. The large grains in the second awl are due to the fact that the object was over-annealed, and this weakened the entire structure (Scott 2010: 56).

Despite the relatively high concentrations of impurity elements in the composition of the oxhide ingots (836.VAR, 834.VAR), on slow cooling the metal has produced an equi-axial, hexagonal grain structure (Scott 1991: 6). The grain sizes of one of the specimens (836.VAR) vary considerably in different parts of the sample (Fig. 8). This can be accepted as evidence that the molten cop-per was poured into the mould in different stages.

Fig. 5: Microstructure (x 50) of a sample of a sickle (854.CF) showing fine and long slightly distorted dendrites.

Fig. 6: Photomicrograph (x 100) of a sample of a sickle (856.CF) showing equi-axed hexagonal grains with straight twin lines. The small grey inclusions are lead. Corrosion and considerable po-rosity.

Fig. 7: Microstructure (x 200) of the cutting edge of the knife (859.CF) showing equi-axed hexagonal grains with strain lines. Inter-granular and stress-cracking corrosions are visible.

Fig. 8: Microstructure (x 50) of an ingot (836.VAR) showing equi-axed hexagonal grains with different sizes; iron-rich alpha phase; round inclusions of copper/iron sulphides. Considerable porosity and corrosion.

Silviya Ivanova, Veselina Rangelova, Deyan Lesigyarski & Ivelin Kuleff

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Additional information about the samples is acquired by SEM-FIB. The spot analyses show the contents and the distribution of chemical elements in selected areas of the specimen. The small grey inclusions in the micro-structure of a sickle (855.CF, Fig. 4) are copper sulphide indicating that the copper is derived from copper sulphide ore or mixed sulphide ore (Scott 2010: 175). The small grey globules throughout the structure of some other samples (e. g., 856.CF) are lead which does not alloy with copper or tin in the casting (Scott 1991: 27). The micrograph of a sample of one oxhide ingot (836.VAR) shows iron particles as iron has a limited solubility in copper above the melting temperature (Craddock 1987:198).

The metallographic study of the finds reveals that most of the metals are alloys (arsenical copper, bronze and brass) with cast dendritic structure. Some of the artefacts have required final shaping and/or hardening. It was carried out by repeated cycles of hammering and an-nealing.

Conclusions

The application of different analytical techniques for ex-amining microstructure and chemical composition of the artefacts from North-East Bulgaria gave the opportunity for comparing and clarifying the results.

In view of the small number of Bronze Age finds exam-ined by the methods of metallography, general inferenc-es about the technological level of the time could not be made. One of the advantages of this metallographic study is that it is among the few works that throw some light on the problem of production technology of Bronze Age finds from Bulgaria. It is worth noting that this ex-ploratory study reveals that the ancient masters’ tech-nological knowledge was at a relatively high level.

At the same time, this investigation of a small group of artefacts seems to indicate that the technology of pro-duction of metal articles from North-East Bulgaria did not undergo fundamental changes during the stages of the Bronze Age. Casting followed by cycles of hammer-ing and annealing resulted in the creation of a product with desired qualities – a balance between hardness, strength and ductility. The objects with foreign influenc-es do not show peculiar microstructural features. The applied working cycles depended mostly on the function of the artefact. The executed metalworking techniques show the ancient masters’ knowledge of the mechanical and forming properties of metals.

Using ICP-AES analyses, it was determined that most of the artefacts under consideration are cast of pure copper or binary alloys - arsenical copper and tin bronze. It is not surprising that the EBA find is made of arsenical

copper and most of the LBA articles – of tin bronze. The oxhide ingots of the LBA are made of copper since they are used for its distribution in the Mediterranean. The appearance of brass among the finds suggests a date to a period after the BA.

Variations in the quantity of some chemical elements in the samples are the result of the use of different ore sources and fabrication techniques of the objects. There is insufficient evidence for any purposeful preparation of a specific type of alloy for the manufacturing of specific objects. Many further analyses will be required to confirm the results and obtain a clear picture of BA copper met-allurgy in Bulgaria.

Acknowledgements

One of the authors (S. I.) would like to express her grat-itude to the American Research Center in Sofia, Amer-ica for Bulgaria Foundation, The American School of Classical Studies at Athens, the Director of Sofia Med S.A. and the members of the projects ‘Collegium Histo-ricum’ (Faculty of History, Sofia University). The authors acknowledge the staff of the project ‘Sub-micron ma-chining and analysis of materials and structures using scanning electron microscopy in combination with fo-cused ion beam’ (Faculty of Physics, Sofia University; DO 02-56/2008).

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