Over the past 10 years, widespread availability in portable XRF (PXRF) instrumentation has resulted in a major paradigmatic shift in how obsidian source studies are conducted. This has resulted in concerns by some about the potential misuse of this emerging technology as well as a host of questions regarding accuracy, precision, and reproducibility.
Following concerns raised in Shackley's recent SAA Archaeological Record essay (see here), Jeff Speakman (UGA CAIS), Steve Shackley (Berkeley), Mike Glascock (U. Missouri), and Arlen Heginbotham (J. Paul Getty Museum) organized a PXRF "shootout" at the 2012 SAA Meeting in Memphis.
The primary purpose of this round robin exercise was to evaluate the current state of inter-laboratory reproducibility when conducting quantitative portable XRF analyses of obsidian. The results of this study which includes data from about 20 institutions will be summarized in an upcoming paper.
The obsidian round robin is the second in a series of exercises designed to evaluate accuracy, precision, and reproducibility among XRF users and is based largely on ASTM standard E1601, Standard Practice for Conducting an Interlaboratory Study to Evaluate the Performance of an Analytical Method.
An earlier study based on the analyses of copper alloys recently was published, and we are currently planning our next interlaboratory comparison (ceramics) which will be held in 2013.
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