THE POSSIBLE FRACTIONATION OF LEAD ISOTOPES IN ANCIENT METALLURGICAL PROCESSES

The possibility of lead isotope fractionation in ancient lead production is examined. Kinetic theory relating to isotopic fractionation in non-equilibrium evaporation is considered and the feasibility of the alteration of lead isotope abundance ratios in ore roasting and smelting is assessed. Previous experimental work is shown to have been inconclusive and conclusions are drawn on the need for further research to quantify the possible extent of fractionation in practice.     

ARCHAEOMETRIC INVESTIGATIONS AT THE UNIVERSITY OF SOFIA,BULGARIA

The paper presents a brief overview and history of archaeometric research using instrumental neutron activation analysis at the Faculty of Chemistry of the University of Sofia. The archaeometric projects are listed and some of the results obtained in the investigations of glass, pottery and metals are described.     

LEAD ISOTOPE ANALYSIS OF ARCHAEOLOGICAL METALS BY MULTIPLE‐COLLECTOR INDUCTIVELY COUPLED PLASMA MASS SPECTROMETRY*

Lead isotope ratios in archaeological silver and copper were determined by MC–ICPMS using laser ablation and bulk dissolution without lead purification. Laser ablation results on high‐lead metals and bulk solution analyses on all samples agree within error of TIMS data, suggesting that problems from isobaric interferences and/or mass bias variations due to the presence of matrix elements are insignificant. Inaccurate laser ablation analyses on low‐lead copper reflect erroneous mass bias corrections from use of a non‐matrix matched standard. However, in most cases, silver and copper are analysable for lead isotopes by bulk dissolution or laser ablation MC–ICPMS with simplified sample preparation.     

A LEAD ISOTOPE DATABASE: THE LOS PEDROCHES – ALCUDIA AREA (SPAIN); IMPLICATIONS FOR ARCHAEOMETALLURGICAL CONNECTIONS ACROSS SOUTHWESTERN AND SOUTHEASTERN IBERIA*

One hundred and twenty‐five new lead isotopic analyses on galena, mainly from the Los Pedroches – Alcudia Valley area of southern Iberia, are presented. These data allow us to define four compositional groups in the ²⁰⁷Pb/²⁰⁶Pb versus ²⁰⁸Pb/²⁰⁶Pb and ²⁰⁷Pb/²⁰⁶Pb versus ²⁰⁶Pb/²⁰⁴Pb diagrams. Group I compositions are intermediate between those previously reported for southeastern and southwestern Iberian ore mineral locations. The compositions of Group II, the largest group, overlap with ore data from southwestern Spain. Groups III and IV have compositions that have never before been identified in this region and are comparable to those from the Sardinian Cu ores, which might explain the previously assumed exotic origin for local Bronze Age artefacts.     

INCISED SLIPWARE PRODUCTION AT CASTELFIORENTINO (FLORENCE): THE ‘VIA BERTINI’ SITE (15TH–17TH CENTURIES)*

This study deals with the physical–chemical and mineralogical–petrographic investigations (OM, SEM–EDS, EPMA, ICP, XRpD, Mössbauer and IR) conducted on first‐ and second‐firing wasters belonging to two types of incised slipware (sgraffito), manufactured at Castelfiorentino between the late 15th and the early 17th centuries. Raw materials, colouring agents and firing products were analysed in order to establish the production technology of the ceramic coatings, by means of detailed microtextural and chemical investigations. The pottery underwent two firing processes: the firing of the white slip‐coated ceramic body and a further firing after application of the glaze. The homogeneity of the raw materials, white slip and glaze is remarkable, and demonstrates the use of well‐established recipes with a constant supply of raw materials from the same places. Highly efficient kiln management during both firings is revealed by body–glaze interface reactions.     

LEAD ISOTOPE ANALYSES OF ISLAMIC POTTERY GLAZES FROM FUSTAT,EGYPT*

Lead isotope analyses have been undertaken on a group of Islamic lead‐glazed pottery artefacts from Fustat, Egypt, spanning the period from the eighth to the 14th century ad , that had previously been the subject of a comprehensive typological, chronological, petrographic and technological study. Comparison of the lead isotope ratios for the glazes with those for lead ores from Egypt, Iran, Tunisia, Anatolia, Greece, Sardinia and Spain provided information on the possible sources of the lead used in the production of the glazes. The results show that the lead used in glaze production by the Islamic potters at Fustat was most probably obtained from distant ore sources in Iran or Tunisia, Sardinia, Spain and the Taurus Mountains. Different ore sources were favoured in different periods and, to a limited extent, for different types of pottery, but at no time did the Fustat potters use the potentially more accessible Egyptian ore sources.     

LEAD ISOTOPE ANALYSIS OF TANG SANCAI POTTERY GLAZES FROM GONGYI KILN,HENAN PROVINCE AND HUANGBAO KILN,SHAANXI PROVINCE

Through the use of MC–ICP–MS, this study analyses the lead isotope ratios of 19 Tang Sancai pottery glazes unearthed from the Gongyi and Huangbao kiln sites. According to their different lead isotope ratios, the two kilns can be grouped separately. The research also suggests that the Gongyi and Huangbao kilns are independent production centres of Tang Sancai in the Tang Dynasty. The data from the Huangbao kiln indicates that the lead in the glazes originates from the Northern China geochemical province, while the data from Gongyi kiln suggests its source as the Yangtze geochemical province. Furthermore, the results obtained for the Tang Sancai pottery indicate that the lead sources for glaze making of these two kilns were very consistent, which suggests that lead isotope analysis could be a helpful method to identify the kilns producing Tang Sancai artefacts.     

IDENTIFICATION AND DIFFERENTIATION OF OPAQUE CHINESE OVERGLAZE YELLOW ENAMELS BY RAMAN SPECTROSCOPY AND SUPPORTING TECHNIQUES*

Using Raman spectroscopy, energy-dispersive X-ray fluorescence and X-ray diffraction, the Pb–Sn–Sb triple oxide yellow and lead–tin yellow have been identified on two pieces of cloisonné enamel (Falangcai) porcelains. Lead–tin yellow and lead antimonate yellow have been identified on famille rose porcelains manufactured before and after 1911, respectively. The replacement of the Pb–Sn–Sb triple oxide yellow by lead–tin yellow and that of the lead–tin yellow by lead antimonate yellow are discussed.     

LEAD ISOTOPE ANALYSES OF BRONZE AGE COPPER‐BASE ARTEFACTS FROM AL‐MIDAMMAN,YEMEN: TOWARDS THE IDENTIFICATION OF AN INDIGENOUS METAL PRODUCTION AND EXCHANGE SYSTEM IN THE SOUTHERN RED SEA REGION*

The results of the lead isotope analysis (LIA) of 15 copper‐base artefacts from the Bronze Age site of al‐Midamman, Yemen, are reported. The LIA data suggest the existence of an indigenous Bronze Age metal production and exchange system centred on the southern Red Sea region, distinct from those in neighbouring regions of Arabia and the Levant. These preliminary results are highly significant for the archaeology of the region, suggesting that local prehistoric copper extraction sites have thus far gone unrecorded, and highlighting the need for systematic archaeometallurgical fieldwork programmes in the countries surrounding the southern Red Sea.     

COMPOSITIONAL VARIATION IN ROMAN COLOURLESS GLASS OBJECTS FROM THE BOCHOLTZ BURIAL (THE NETHERLANDS)*

We investigated the major and trace element composition and Pb and Sr isotope characteristics of a series of about 20 colourless glass objects from a single high‐status Roman burial from the Netherlands (Bocholtz). The major elements show a relatively homogeneous group, with one outlier. This is corroborated by the Sr isotopes. Based on the Sb and Pb content, three major groups can be discerned, with two other outliers. This grouping is corroborated by the contents of the trace elements Bi, Sn, Ag, As and Mo, and by variations in lead isotopic ratios. On the basis of these results, we conclude that the glass of all objects was probably made with sand and lime from the same source. The variation in trace elements and lead isotope composition is most likely the result of variations in the composition of the sulphidic antimony ore(s) that were used to decolourize the glass. The composition of the Bocholtz glass is compared with that of other Roman glass, and implications for production models, trade and use of colourless glass objects are discussed. On the basis of isotopic and major element variation, we conclude that the antimony ore presumably originated from different mines.