Is obsidian sourcing about geochemistry or archaeology? A reply to Speakman and Shackley

Abstract The response from Speakman and Shackley to my paper highlights a number of important issues currently facing archaeological sourcing research. Many of these issues, however, have little to do with HHpXRF itself and more to do with an artificial crisis triggered by specialists' concerns about a hitherto restricted technique becoming available to a wider community. Despite their mantra of “validity and reliability,” Speakman and Shackley erroneously equate these two concepts with the accuracy of an instrument's measurements. Additionally, they mischaracterise a self-contained test, conducted with specific parameters (i.e., “off-the-shelf” operation), as an endeavour to facilitate or endorse poor-quality data. Paradoxically, their disparagement of experimental internal consistency as “silliness” is incongruous with their own data. Furthermore, a discussion focused on handheld instruments is obfuscated by their inclusion of desktop instruments that are “portable” only in the sense of luggable to an electrical outlet in a laboratory context. Most troubling is that they envision themselves as the arbiters of science vs. “playing scientist.” Contrary to their claims, HHpXRF proliferation will improve reproducibility and archaeological results.