Hi, Rap and Ebbie. Thanks for the info on obsidian. As a Midwesterner, I have never seen obsidian in the wild, not even on my trips out west.

Then somebody told me about Glass Butte in Oregon, clearly a good place to look, (but not the only place.) That would be interesting to see sometime.

http://northwestrevealed.com/2013/09/17/rivers-of-glass-glass-butte-oregon

#, that's interesting about obsidian for surgical use.