Archaeometry 50 (1)

The authors examine the precision and accuracy of non-destructive EDXRF for basalt artefacts by analysing varying size and weathering characteristics. The experiments identified no appreciable effect in reproducibility or measured composition due to thickness (down to 1 mm) or natural weathering of pre-contact flake scars for the seventeen elements measured in the study. Samples with surface area less than 100 mm2, however, show significant variability in measured composition and reproducibility.

Tin-based opacifiers (lead stannate yellow and tin oxide white) were first used in glass production for a short period in Europe from the second to the first centuries BC and then again throughout the Roman and Byzantine Empires from the fourth century AD onwards. Tin oxide was also used in the production of Islamic opaque glazes from the ninth century AD, and subsequently in enamels applied to Islamic and Venetian glasses from the twelfth century AD onwards. A selection of published analytical data for the tin-opacified glasses, enamels and glazes is summarized, and the methods used in their production are reassessed. The phase transformations occurring when mixtures of lead oxide, tin oxide and silica are fired are investigated with high temperature X-ray diffraction (XRD) using a synchrotron radiation source, and these results are used to explain the observed differences in the glass, enamel and glaze compositions. Possible reasons for the use of tin-based opacifiers in the second to first centuries BC, and for the switch from antimony- to tin-based opacifiers in the fourth century AD are suggested, and the possible contexts in which tin-based opacifiers might have been discovered are considered. The introduction of tin-opacified glazes by Islamic potters in the ninth century AD is discussed in terms of technological transfer or independent invention.

Stable carbon and nitrogen isotope compositions were measured on human and faunal bones, sampled from the Neolithic chambered tomb of Hazleton North, Gloucestershire. The values were used to characterize the diet of the burial community as a whole. Humans were higher in δ15N by 4.5--5.0o/oo relative to animal δ15N, from which the authors conclude that, based on currently accepted interpretations of isotopic data, the humans consumed a diet that was very high in meat or animal products (75% by weight of protein). Comparison was also possible between cortical and cancellous femoral collagen, with the results showing no significant difference for the adult humans. The sample of human isotopic values showed little variability, in contrast to that found in the domestic and wild animals from the site (including cattle, pigs, sheep and deer). The authors suggest that this is due to local environmental differences, rather than to environmental change over time or physiological differences between individual animals, and that this pattern is likely to hold for many other archaeological sites when analysed with sufficient statistical weight.

The paper examines some approaches to the statistical analysis of data arising from both geochemical and mineralogical techniques, including `mixed-mode' methods where both types of data are incorporated into analysis. The approaches are illustrated using data derived from eighty-eight Late Bronze Age transport jars from Crete. Results suggest that the mixed-mode approach can provide additional insight into the data. Includes