Obsidian is a kind of volcanic glass and was highly prized for making certain kinds of stone tools. Obsidian forms at places of relatively small outflows of magma, or liquid rock. Small flows can cool quickly, which allows the formation of a glassy crystalline structure ideal for stone tool manufacture. Small flows also represent a small sample of well-mixed magma, and thus each little patch of obsidian may share a very distinctive chemical signature. This signature, usually identified by trace elements such as Strontium, Zirconium, Yttrium and Rubidium, then allows for the chemical fingerprinting of each source. Any obsidian artifact found, whether at a source or not, can also be “fingerprinted” and then compared to a catalogue of known obsidian ources. Since the artifacts don’t move around on their own but only through the agency of humans, the distribution of obsidian artifacts is a proxy measure for the movement and interaction of people. When you have hundreds or thousands of such artifacts and a large database of known sources, then you can start to see large scale, long-term social interaction emerge from the silent archaeological record. Most obsidian isn’t visually distinctive enough to sort out by eye alone, so these geochemical methods are essential.
So far, so Archaeology 101. I was really happy to find that Oregon’s Northwest Research Obsidian Studies Laboratory has a web site not which not only solicits business, but is a highly educational and informative site about many aspects of obsidian analysis, with a focus on the Northwest.
For example, they have a handy series of maps showing western United States known obsidian sources (as well as the latitude and longitude of these sources here and a simple google maps here – nick, fire up your truck, and GPS). Some of the detailed maps of Oregon are incredible – who knew how many distinct sources there were, so close together? Also, there sure are a lot of known sources in Washington State – why then is so much BC obsidian coming all the way from Oregon? Canadian sources are not yet mapped. They have some sample reports available for download, and some extensive bibliographies. Their FAQ is comprehensive and informative.
The research page contains a lot of interesting links, including analysis of Luther Cressman’s mysterious Kraft Dairy Fresh Caramels box of artifacts, and Bone Cave lava tubes. I was also intrigued to see that Obsidian Hydration is back on the table as a dating technique, and that this lab routinely does Fine-Grained Volcanics (basalts, andesites) X-Ray Flourescence as well – including a major source they place at Watts Point (near (Britannia Beach) but which is not mapped very clearly (see this page). Work on these “crappy coastal lithics” could be very cool: I am thinking of the apparent quarry site Parks Canada recently identified on the Gulf Islands, for example, and whether these lousy lithics were widely sourced or opportunistically scavenged from tills.
Incidentally, they are currently offering research support targeted at Graduate Students wanting to work on geochemical work in BC – this could be a great project for someone to sort out the various Edziza sources (reminds me, I have a lump of unsourced Edziza obsidian on my desk which I picked up in about 1984 at about 8000 feet). They also have a series of 360 degree panoramic views of some obsidian sources (e.g., Collier Cone) as well as their lab and so forth. They’ve even started a youtube channel.
A blog (not too many entries yet) contains the first written confirmation I have seen that the longstanding BC “Central Coast A” mystery-source obsidian is now known to be from the head of Kingcome Inlet, which is a substantial break through in understanding the distribution networks of NE Vancouver Island and the adjacent mainland. I heard about this through the grapevine but nice to have a little detail.
Sample analysis starts at 45$ and then decreases depending on volume. It would be great if there was a requirement for obsidian to be sourced during BC CRM studies — I know it often is anyway, but the marginal cost is minimal and the accumulated benefits could be enormous so why not make this a minimum requirement of a permit?
Anyway, this is a full and interesting site which goes well beyond the narrow frame of a commercial service and provides useful background information and exciting case studies to whet the appetite for more obsidian studies!