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Analytical protocols

At the MAX Lab all artefacts are analyzed whole and non-destructively on the Thermo Scientific ARL Quant’X energy-dispersive x-ray fluorescence spectrometer

For more information download the EDXRF manual.  Each piece having first been cleaned in an ultrasonic tank with distilled water for ten minutes.

The spectrometer is equipped with a ultra-high flux peltier air cooled Rh x-ray target with a 125 micron beryllium (Be) window, an x-ray generator that operates from 4 to 50 kV/0.02 to 1.0 mA at 0.02 increments and a 2001 min-1 Edwards vacuum pump for the analysis of elements below titanium (Ti).

Data are acquired with a pulse processor and analog to digital converter. At present our obsidian analyses involve the recording of a minimum of 15 elements, including the major elements: titanium (Ti), manganese (Mn) and iron (Fe), plus trace elements nickel (Ni), copper (Cu), zinc (Zn), gallium (Ga), rubidium (Rb), strontium (Sr), yttrium (Y), zirconium (Zr), niobium (Nb), barium (Ba), lead (Pb) and thorium (Th).

In order to evaluate these quantitative determinations, instrument data are converted to concentration estimates through reference to various standards,

including those certified by the US Geological Service [http://www.usgs.gov/] and Geological Survey of Japan (AGV-2, BCR-2, BHVO-2, BIR-1a, GSP-2, JR-1, JR-2, QLO-1, RGM-2, SDC-1, STM-2, TLM-1 and W-2a). In turn, the standard RGM-2 (USGS) is analyzed during each sample run to check machine calibration and accuracy. The data are then translated directly into Microsoft Excel for Windows software for manipulation and analysis. Really small artefacts, or those exhibiting anomalous results, are re-run to ensure accuracy and precision. Our analytical protocols and methods follow those devised by Shackley (2005; Poupeau et al. 2010: 2711).

In attempting to provenance an artefact’s raw material, we compare its chemical signature with those of source samples run by the MAX Lab under the same conditions.

At present the lab has a large range of geological samples from obsidian sources across the Eastern Mediterranean and Mesoamerica, plus smaller quantities from the Western Mediterranean, Trans-Caucasia, Japan, Peru and the US.

References