LA–ICP–MS,SEM–EDS AND EPMA ANALYSIS OF EASTERN NORTH AMERICAN COPPER‐BASED ARTEFACTS: IMPACT OF CORROSION AND HETEROGENEITY ON THE RELIABILITY OF THE LA–ICP–MS COMPOSITIONAL RESULTS*

This study discusses the relevance of compositions obtained using laser ablation – inductively coupled plasma – mass spectrometry (LA–ICP–MS) for the purpose of identifying the provenance of copper‐based artefacts found in Virginia at Native American sites dated from the 16th to the 18th centuries. Ten artefacts were investigated by scanning electron microscopy – energy dispersive spectrometry (SEM–EDS) to visualize the corrosion and characterize the heterogeneities in the metal and electron probe micro‐analysis (EPMA) to determine separately the compositions of the intact metal and of the corrosion product. It is shown that the corroded surfaces are highly depleted in zinc but that representative concentrations can be determined by sampling the deeper, uncorroded metal. In contrast, lead values are highly variable because of the heterogeneous distribution of this metal within the bulk copper. Despite these problems, brass is easily identifiable and American native copper and European smelted copper can be unambiguously distinguished with LA–ICP–MS on unprepared artefacts using As, Ag, Ni and Sb trace elements.     

SERIPHOS SURFACES: A STUDY OF COPPER SLAG HEAPS AND COPPER SOURCES IN THE CONTEXT OF EARLY BRONZE AGE AEGEAN METAL PRODUCTION

Kephala and Phournoi, on the island of Seriphos, add to a growing number of EBA metal production sites identified in the south‐central Aegean. Analytical examination of samples from the two sites addressed the technological parameters of the copper smelting process, indicating the use of mixed oxidic and sulphidic copper–iron ores to produce unalloyed copper with minute copper sulphide inclusions. A preliminary geological reconnaissance of the island identified several small copper mineralizations, one of them close to the site of Kephala. Nevertheless, the ore sources used remain unclear. Comparisons are made with other contemporaneous neighbouring smelting sites.     

SHAFT‐HOLE AXES FROM SLOVENIA AND NORTH‐WESTERN CROATIA: A FIRST ARCHAEOMETRIC STUDY ON ARTEFACTS MANUFACTURED FROM META‐DOLERITES*

A group of Copper Age shaft‐hole axes from Caput Adriae (northeastern Italy, western Slovenia and northwestern Croatia) manufactured using meta‐dolerite have been analysed for major and trace elements. All the samples show magmatic textures and well recognizable relicts of primary mineralogical phases. Petrographic observations suggest an ophiolitic provenance of the protolithic source(s) while geochemical data indicate that the original magmas originated in a fore arc or pre arc tectonic setting. Strong similarity has been found with several lithotypes from the Banija Ophiolite Complex (Croatia), here indicated as the most probable source area. Considering the available archaeometric data about shaft‐hole axes found in northern Italy and Caput Adriae in comparison to those of axe blades discovered in the same area, it emerges that there is a utilization of different rock types, the source of which appears to be quite close to the discovery sites. In the investigated area the shaft‐hole axes are largely made from ophiolitic‐related rocks which are associated with copper deposits. Consequently there may have been a relation between the localization of the geological sources of shaft‐hole axes and the development of metallurgical activities.     

MINERALOGY OF MEDIEVAL SLAGS FROM LEAD AND SILVER SMELTING (BOHUTÍN,PŘÍBRAM DISTRICT,CZECH REPUBLIC): TOWARDS ESTIMATION OF HISTORICAL SMELTING CONDITIONS*

Slags from the Pb/Ag medieval (14th century) smelting plant located at Bohutín, P?íbram district, Czech Republic, were studied from the mineralogical and geochemical points of view. Two types of slags were distinguished: (i) quenched slags formed mainly by Pb‐rich glass and unmelted residual grains of SiO₂ and feldspars, and (ii) crystallized slags mainly composed of Fe‐rich olivine (fayalite) and glass. The mean log viscosity value of the slags calculated for 1200°C was 2.119 Pa s. The morphology of olivine crystals was used to estimate the cooling rates of the melt, for some slags indicating rates > 1450°C/h. The projection of the bulk composition of slags onto the SiO₂–PbO–FeO ternary system was used for rough temperature estimates of slag formation, lying probably between 800 and 1200°C.     

STUDY OF ANCIENT GREEK COPPER COINS FROM NIKOPOLIS (EPIRUS) AND THESSALONIKI (MACEDONIA)

Ancient copper coins from the Greek cities Nikopolis in Epirus and Thessaloniki in Macedonia, minted during Roman imperial times (31 BC to AD 268), were analysed non-destructively by proton induced X-ray emission, after removal of the patina. An intercompar-ison study using different analytical methods was also performed on five coins. Eleven elements were analysed quantitatively on all coins. Statistical analysis of the results was performed for their presentation in the form of dendrograms. Finally, the variations in the concentrations of some individual elements from emperor to emperor were examined.     

ARCHAEOLOGICAL AND CHEMICAL RESEARCH ON SEDIMENTS AND CERAMICS AT POLIDEPORTIVO (SPAIN): AN INTEGRATED APPROACH*

This paper proposes a preliminary approach to the integration of archaeological evidence and various chemical analyses (phosphorus and lipid) on sediments and ceramics. Phosphorus and organic matter analyses are, thus, used for the study of sediments, and lipid analyses for pottery from structure 19 of the Late Neolithic—Early Copper site known as ‘Polideportivo’, Martos, southern Spain. The results of both types of analysis point to a predominantly domestic function for this structure.     

PHOSPHORUS ANALYSIS AT ARCHAEOLOGICAL SITES: AN OPTIMIZATION OF THE METHOD AND INTERPRETATION OF THE RESULTS

The application of phosphorus analysis to archaeological contexts can be considerably improved through ultrasonic extraction and the statistical evaluation of results through an analysis of variance. Such tools make the archaeological application of phosphorus analysis faster as well as more economical and coherent. This paper describes the features of these tools and provides a practical case: the Late Neolithic—Early Copper phase of the site ‘Polideportivo’in Martos, southern Spain.     

‘DE CAERIMONIAE’ TECHNOLOGICAL CHOICES IN COPPER‐SMELTING FURNACE DESIGN AT EARLY BRONZE AGE CHRYSOKAMINO,CRETE*

The excavation of a number of Early Bronze Age sites in the Aegean has recovered perforated ceramic fragments. Archaeometallurgical analysis of slag adhering to these fragments indicates that they are the remains of copper‐smelting furnaces. Despite compelling analytical data supporting this identification, no attempt has been made, thus far, to establish how these unusual furnaces may have operated. The use of perforations is poorly understood and can be considered a counter‐intuitive solution for the reduction of oxidic copper ores. The experiments reported here explore the possible technological choices made by the ancient metalworkers of Chrysokamino to ensure the effective reduction of copper minerals. Temperature data and slag samples were obtained to ascertain the technical performance of the furnace structure with, and without, perforations. Possible reasons are given for the use of a perforated design, and the implications of such technological choices are considered.     

TOOLS TO QUALIFY EXPERIMENTS WITH BLOOMERY FURNACES*

Five experimental bloomery iron ore smelts were carried out in a reconstruction of an early medieval furnace of the Boécourt type (Switzerland). A part of the bloom from the most successful experiment was forged to a billet. Starting materials and products were weighed, described and chemically characterized (ICP-MS, LA-ICP-MS and WD-XRF). The calculation of the yield and mass balance based on the chemical analyses from the ore (optimum) and from the ore, furnace lining, slag and ash (applied) allow the determination and quantification of the materials involved in the process. This permits the interpretation of the quality of the experiments. The chemical characterization of metal produced from hematite ore from the Gonzen Mountains in Switzerland gives archaeologists the possibility to compare the metal of iron artefacts to metal from this mine. Finally a good agreement between experiments and archaeological reality can be shown.     

Technical Studies on the Bronze Age Metal Artefacts from the Graveyard of Deh Dumen,South‐Western Iran (Third Millennium BC)

During the excavations of the graveyard at the site of Deh Dumen in south‐western Iran, 15 graves from the Early/Middle Bronze Age were uncovered that contained a variety of metallic artefacts. This paper reports on the analysis of nine metal artefacts, including eight broken vessels and a decorative strip that covered the handle of a dagger. The ICP–MS results showed that the bodies of the vessels are made of tin bronze alloy with variable amounts of tin, while the internal piece of the base of one vessel is made from an arsenical copper alloy. Further, the metallic strip is a thin sheet manufactured with partially pure silver. Microanalytical and microstructural information yielded by SEM–EDS revealed elongated Cu–S inclusions and lead globules as various phases formed in bronze solid solution. This study presents some information about the transition from arsenical copper to bronze metallurgy in the third millennium bc in south‐western Iran.