Of tektites and other rocks
Ok, I promised to talk (blog? I'm still kinda iffy about using "blog" as a verb) about tektites. In the course of our dig at Junction, we recovered a flake of black, glassy material. Our immediate reaction was "Holy shit, obsidian!" Obsidian is volcanic glass formed from superheated sand (or something like that). Naturally, it's most commonly found in the vicinity of volcanoes. In the US, this would be the Rocky Mountain states. So finding obsidian in Texas is a big deal because the nearest source is somewhere in New Mexico. When you have it, you can say "Aha, evidence of a long distance trading network!" which makes your basic CRM report a bit more sexy.
When our geomorphologist (I mentioned him before briefly, and I now realize that the previous paragraph was written in the manner in which he speaks) dropped by to check it out, he said, "Or, it could be a tektite." When we asked what that was, he said something to the effect of "It comes from when meteorites strike the earth, in this case the Chesepeake Bay area around 30,000 years ago." So naturally, we figured he was messing with us (he spent a lot of time in Britain and thus has an odd sense of humor) and kept digging. Then he said, "The way you can tell a tektite from obsidian is to use a blow torch. I happen to have a blow torch in my truck." As you can imagine, this got our attention. If you read the link, you can see that tektites have almost no water or gases in them, so blow torching them has no effect. Obsidian will foam due to the water and gases escaping. Unfortunately, this test destroys the obsidian, and so we didn't actually do a field test (it's a rather small flake and not easily replaceable).
Upon doing some research for this post, I learned about Bediasite, which is the tektite specific to Texas and resulted from a meteorite impact in the Chesapeake Bay area 30 MILLION years ago. So Charles wasn't messing with us at all. It's also interesting because there have been a number of unsourced obsidian artifacts discovered in Texas, which may actually be tektites. Now, if only we can convince the various curation centers to let us take a blowtorch to their obsidian!
When our geomorphologist (I mentioned him before briefly, and I now realize that the previous paragraph was written in the manner in which he speaks) dropped by to check it out, he said, "Or, it could be a tektite." When we asked what that was, he said something to the effect of "It comes from when meteorites strike the earth, in this case the Chesepeake Bay area around 30,000 years ago." So naturally, we figured he was messing with us (he spent a lot of time in Britain and thus has an odd sense of humor) and kept digging. Then he said, "The way you can tell a tektite from obsidian is to use a blow torch. I happen to have a blow torch in my truck." As you can imagine, this got our attention. If you read the link, you can see that tektites have almost no water or gases in them, so blow torching them has no effect. Obsidian will foam due to the water and gases escaping. Unfortunately, this test destroys the obsidian, and so we didn't actually do a field test (it's a rather small flake and not easily replaceable).
Upon doing some research for this post, I learned about Bediasite, which is the tektite specific to Texas and resulted from a meteorite impact in the Chesapeake Bay area 30 MILLION years ago. So Charles wasn't messing with us at all. It's also interesting because there have been a number of unsourced obsidian artifacts discovered in Texas, which may actually be tektites. Now, if only we can convince the various curation centers to let us take a blowtorch to their obsidian!
Labels: archaeology, archeology, meteorite, obsidian, tektites, Texas
posted by jlowe | 7:25 PM
4 Comments:
cool. fire! fire!
Awesome. I talked to Shackley about it briefly and he pretty much affirmed what you said, though there is some obsidian that does not foam when you put it under a blow torch. Shackley is the best ever - I hope you get to meet him.
"take a blowtorch to their obsidian"
Is that a euphemism?
And all sorts of things are now verbs thanks to the almighty webernet - blog, google, myspace, favorite. I've just come to accept it.
don't forget hitspace (verb).
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