Title:
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EPMA, XRF and LA-ICP-MS analysis of archaeological artifacts : applications to provenancing
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Chemical data obtained through LA-ICP-MS, EPMA and XRF analysis have been used
to investigate the potential for provenancing archaeological.artefacts. By combining
chemical analysis with multivariate statistical analysis (pCA and cluster analysis) a
more robust and objective method of classification and provenancing can be obtained.
Modem glass bottles were used as an analogue for Islamic Bahraini glass samples, to
test the application ofXRF analysis. For the modem glass samples which were
homogeneous, with the chemistry being tightly controlled during manufacture and were
free from alteration by weathering, an accurate method of provenancing was obtained.
The colour of the glass was found to be a confounding factor. By restricting statistical
analysis to a single colour of sample, a wide range of bottles from around the world
were accurately grouped into the region where they were manufactured.
Applying the same methods to the Islamic Bahraini glass it was found that the amount
of weathering was a major confounding factor, as was the colour of the sample. When
performing PCA and cluster analysis it was found that samples clustered together
depending on their degree of weathering or how well weathering products had been
removed prior to analysis. The size of sample for XRF was found to have an effect on
the accuracy of the analysis, caused by x-ray attenuation within the sample and
therefore requiring a ZAP like correction to be made to major and minor elemental data.
No effect was seen when performing PCA and cluster analysis.
Variations in the amounts of MgO and K20 present indicate that plant ashes were used
as the soda source and not natron. There may be slight differences in the plants or the
parts of plants used in manufacture. Ah03 contents also indicate differences in the
silica source but neither of these appear to be related to the period of time or location
where the samples were found. It is possible that raw glass was brought to Bahrain for
re-working or that finished items were traded from elsewhere as no evidence was found
in the samples for primary glass production (frit).
The analysis of carnelian beads from India and Mali by LA-ICP-MS was found to be
difficult. Although the heterogeneity within a carnelian bead was found to be much less
than that seen in samples of agate, the chemical variations within in a sample was still
large and would outweigh any differences between sources.
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