ELECTROCHEMISTRY AND AUTHENTICATION OF ARCHAEOLOGICAL LEAD USING VOLTAMMETRY OF MICROPARTICLES: APPLICATION TO THE TOSSAL DE SANT MIQUEL IBERIAN PLATE

An essentially non‐invasive electrochemical methodology addressed to the authentication of archaeological lead is described. The method is based on the record of the voltammetric response of nanosamples from the archaeological artefact mechanically transferred to a graphite ‘pencil’ electrode in contact with aqueous buffers. Three diagnostic criteria for authentication are described based on the appearance of: (i) oxidative dissolution signals for trace metals like copper, arsenic, antimony and, often, tin and silver accompanying stripping peaks for lead, (ii) peak potential shifts for reduction peaks for patination products, and (iii) the presence of reduction peaks for PbO₂. The method is applied to the authentication of an Iberian lead plate from the Tossal de Sant Miquel (Llíria, Spain) site using a series of genuine and false pieces from different provenances in the Valencian region (Spain).     

MEDIEVAL LEAD GLASS IN CENTRAL EUROPE

In Trommsdorfstraße, Erfurt, a glass‐processing workshop has been excavated, which produced lead glass rings and beads in the 13th century. This workshop produced two different lead glasses. The first, a high‐lead glass, could be found throughout Europe, from England to Russia. However, another newly defined type of glass could be identified (Central European lead–ash glass). This can be demonstrated by analysing the literature, and it has been found in eastern Germany, Poland, Slovakia and the Czech Republic. A Slavic lead–ash glass with the same ash content as the Central European lead–ash glass but lower amounts of lead was produced in Eastern Europe. In western Germany, another type of ash (beech ash) was used to produce a wood‐ash lead glass. Lead‐isotope analysis proved that the same source of lead was used for the wood‐ash lead glass and the high‐lead glass in western Germany and the two types of glass from Erfurt.     

REFINING ESTIMATES FOR THE SEASON OF SHELLFISH COLLECTION ON THE PACIFIC NORTHWEST COAST: APPLYING HIGH‐RESOLUTION STABLE OXYGEN ISOTOPE ANALYSIS AND SCLEROCHRONOLOGY

Stable oxygen isotopes from estuarine bivalve carbonate from Saxidomus gigantea were analysed combined with high‐resolution sclerochronology from modern and archaeological shells from British Columbia, Canada, to determine the seasonality of shellfish collection from the archaeological site of Namu. The combination of high‐resolution sclerochronology and a micro‐milled sampling strategy for δ¹⁸O analysis permits a precise estimate of archaeological seasonality, because seasonal freshwater influxes and changes in temperature have dual effects on the δ¹⁸O value of the shell. Sclerochronological analysis identifies the timing and duration of growth that is temporally aligned to stable oxygen isotope results, since δ¹⁸O_shell appears to be strongly influenced by seasonal inputs of very low δ¹⁸O snowmelt‐water from adjacent coastal mountain ranges. The results show that shellfish were collected year‐round at this site over a 4000‐year period, and these data combined with other zooarchaeological lines of evidence support the interpretation of year‐round occupation.     

The early roman imperial AES coinage II: Tracing the copper sources by analysis of lead and copper isotopes—copper coins of Augustus and Tiberius*

Lead and copper isotopes of Roman Imperial copper coins (denominations as and quadrans) were analysed by MC–ICP–MS. We concentrated on well‐dated coins minted at the official mint of Rome under the Emperors Augustus and Tiberius (between 16 bc and ad 37). The lead isotope results were compared with published lead isotope data of ore bodies from the Aegaean, Cyprus, Italy and Spain, in order to fingerprint the sources of Roman copper. During the Augustan period the main copper supply, as judged from the copper coins, is from Sardinia and south‐east Spain, with minor contributions from Tuscany. Except for Tuscany, this continued into the Tiberian period, when Cypriot copper also appears. Augustan quadrantes and late Tiberian asses came solely from the Rio Tinto area in south‐west Spain. Copper isotopes were applied here for the first time to systematic archaeometric studies. They are supplementary to lead isotopes and allow further grouping and classification of the copper coins.     

The Use of Strontium Isotope Analysis to Investigate Tiwanaku Migration and Mortuary Ritual in Bolivia and Peru

Strontium isotope analysis is applied in South America for the first time in order to investigate residential mobility and mortuary ritual from ad 500 to 1000. While Tiwanaku‐style artefacts are spread throughout Bolivia, southern Peru and northern Chile during this time, the nature of Tiwanaku influence in the region is much debated. Human skeletal remains from the site of Tiwanaku and the proposed Tiwanaku colony of Chen Chen have been analysed to test the hypothesis that Tiwanaku colonies, populated with inhabitants from Tiwanaku, existed in Peru. Strontium isotope analysis supports this hypothesis by demonstrating that non‐local individuals are present at both sites.     

ROMANO‐EGYPTIAN RED LEAD PIGMENT: A SUBSIDIARY COMMODITY OF SPANISH SILVER MINING AND REFINEMENT*

Samples of red pigment from a group of seven Roman‐period Egyptian mummies, known as red‐shroud mummies, are investigated. Elemental analysis by inductively coupled plasma time‐of‐flight mass spectrometry (ICP–TOFMS) shows that the samples contain mostly Pb (83–92% by weight), along with 0.2–2.0% Sn. All of the samples are found to have similar trace element distributions when normalized to the continental crust, suggesting that they share a common geological origin. Lead isotope ratios are found to match the mixed lead sources typically associated with Rio Tinto, Spain – a site extensively mined for silver during the first century ad . Raman microspectroscopy identifies the major phase of each sample to be red lead (Pb₃O₄) with a minor phase of lead tin oxide (Pb₂SnO₄). Lead tin oxide does not occur naturally, and its incidental occurrence within the sample indicates that the material was heated under oxidative conditions at temperatures in excess of 650°C. In archaeological contexts, the high‐temperature oxidative treatment of lead is typically associated with metallurgical refinement processes such as cupellation. Based on this evidence, it is argued that the pigment was produced out of litharge associated with silver cupellation at the Rio Tinto site.     

MATHEMATICS,STATISTICS AND ARCHAEOMETRY: THE PAST 50 YEARS OR SO*

This review of developments in the use of mathematics and statistics in archaeometry over the past 50 years is partial, personal and ‘broad‐brush’. The view is expressed that it is in the past 30 years or so that the major developments have taken place. The view is also expressed that, with the exception of methods for analysing radiocarbon dates and increased computational power, mathematical and statistical methods that are currently used, and found to be useful in widespread areas of application such as provenance studies, don't differ fundamentally from what was being done 30 years ago.     

Impact of Pollution at a Stone Age Rock Art Site in Oslo, Norway, Studied using Lead and Strontium Isotopes

Naturally occurring strontium and lead isotopes were used to study the impact of anthropogenic pollution on a c. 4500-year-old rock carving in Oslo, Norway. Strontium analyses have shown that road-salt from de-icing of a nearby road has accumulated in the soil surrounding the carving. Upon rainfall this salt is redissolved and drains over the rock carving. Analyses of the lead isotopic system have confirmed the impact of traffic from the nearby road on the rock carving site, but also indicate other sources of lead in the Oslo area and pollution in general. The rock carvings at Ekeberg are at high risk as, apart from natural weathering, they are exposed to the deposition of road salt, emissions from nearby traffic, local and long distance atmospheric pollution and meteorological inversion effects during the winter.     

LEAD GLAZES IN ANTIQUITY—METHODS OF PRODUCTION AND REASONS FOR USE*

Transparent high lead and tin-opacified lead-alkali glazes have been extensively used throughout Europe and the Near East from their first appearance in the Roman era and the tenth- to eleventh-century Islamic world, respectively, up until the present day. Using, to a large extent, information which is widely scattered through a diverse range of literature, the methods employed in the production of these two glaze types are first outlined and their merits are then compared with those of alkali glazes in terms of ease of preparation of the glaze mixture, ease of application of the glaze, ease of firing, cost of production, glaze-body fit and visual appearance. The principal advantages of transparent high lead glazes as compared to alkali glazes are shown to be ease of preparation and application of the glaze suspension, low susceptibility to glaze ‘crazing’ and ‘crawling’ and high, optical brilliance. Factors that influence the choice of tin-opacified lead-alkali glazes include ease of production of tin oxide by melting tin and lead metals together; a reduced risk of reduction of lead oxide to lead metal and consequent blackening of the glaze; and, again, low susceptibility to ‘crazing’ and ‘crawling’. Limits of current knowledge regarding these two glaze types and requirements for future research are outlined.     

NUCLEAR MAGNETIC RESONANCE SPECTROSCOPIC AND ISOTOPIC ANALYSIS OF CARBONIZED RESIDUES FROM SUBARCTIC CANADIAN PREHISTORIC POTTERY

Late prehistoric pottery is found in abundance at archaeological sites around Southern Indian Lake. Black residues, found on the two dominant vessel forms, flat plates and round pots, are presumed to be the remains of prehistoric meals. ¹³C cross-polarization magic-angle-spinning nuclear magnetic resonance spectroscopy (CPMAS NMR) and¹³C and¹⁵ N isotopic ratios and C/N ratios are used to reconstruct prehistoric diet and to shed light on possible uses for the plates. Samples of foods were cooked in clay pots, on a wood fire, to simulate the conditions of burning that could have produced the residue. Decomposition of carbohydrates, protein, and fat during cooking is studied with ¹³C CPMAS NMR, and the effect of cooking on isotopic and C/N ratios documented. Predominantly fish and fat were cooked in the pots, whereas the residues from plates contain a greater proportion of fat and could have been used as frying pans or possibly as fat-burning lamps placed on the ashes of a wood fire.