Frahm et al (2013) have recently demonstrated the ability to source obsidian artifacts in the field in just under 10-seconds. A portable XRF is a device that uses x-ray flourescence to determine the chemical composition of rocks. It’s a handy device for archaeologists because it can tell us a bit about pigments such as that used on rock art, but it was used by the authors of this paper in the Journal of Archaeological Science to rapidly determine the sources of obsidian artifacts in Armenia, one of the richest landscapes for obsidian in the world.
Obsidian is a volcanic glass that forms during the rapid cooling of lava without crystallization and the physical make up of obsidian is dependent upon the volcano it originates from. Each volcano leaves its own “fingerprint” -or unique chemical signature in the obsidian which remains for millions of years. Obsidian was a highly prized (and still is) resource for tool use since it can be flaked to create some of the sharpest cutting edges known. As you can imagine, obsidian was traded far and wide.
Once one knows the chemical make up of each source of obsidian (thank you geologists!), one need only compare the pXRF data to that database of known sources.
According to Frahm:
“Obsidian sourcing has, for the last 50 years, involved chemical analysis in a distant laboratory, often taking five minutes per artefact, completely separate from the process of archaeological excavation. We sought to bring new tools for chemical analysis with us into the field, so we can do obsidian sourcing as we excavate or survey an archaeological site, not wait until months or years later to learn the results. We can now analyse an obsidian artefact in the field, and just 10 seconds later, we have an answer for its origin.”We carried out the research in Armenia because it has one of the most obsidian-rich natural and cultural landscapes in the world, and the lithic assemblages of numerous Palaeolithic sites are predominantly, if not entirely, composed of obsidian.”
In their words, they’ve switched the role of sourcing obsidian artifacts “from the context of ‘white lab coats’ to that of ‘muddy boots.”
Frahm, Ellery; et al (2013) Ten Seconds in the Field: Rapid Armenian Obsidian Sourcing with Portable XRF to Inform Excavations and Surveys. Journal of Archaeological Science, In Press.