It sure looks like obsidian to me. In eastern Oregon there is a mountain called "Glass Butte." That mountain is loaded with obsidian flows. Further east of Glass Butte is a mountain called, "Wagon Tire Mountain." It doesn't have the flows, but has lots of porous lava along with what I call a lower grade of obsidian. Those rocks appear to have been blown out of the mountain, (Glass Butte?) and landed in the lake that at one time covered the great basin. In my experience, the rock on Wagon Tire works like obsidian, but it's not the quality that's found on Glass Butte, which is only a few miles away. That's just from my experience. I also have a large bi-face point found locally, when they were digging footings for an apartment building. I figure the point is lower grade obsidian, but someone poo-pooed my idea and said it was basalt. I always figured basalt was kind of a country rock that is everywhere, and there is no obsidian or rock like it native to where I live. So I might be barking up the wrong tree, and need to learn a lot more about rocks.
