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Hi Guys and Gals,
Our annual flyfishing trip to the McCloud River south east of Mt Shasta was last week. Late snows have the mountain wearing a heavy ermine coat, and the run off is cold and deep. The trout are still hiding out waiting for warmer lower spring waters but smaller streams are productive. I hooked and released 6 nice rainbows one day, and my group of 6 guys must have hooked into 80 fish in 4 days - all lovingly released.
Anyway flat spots are at a premium there in Ishi"s home country and our campsite was an old village. The ground is littered with obsidian flakes from tool production. Man made flakes from working stone are obvioous to the trained eye. The former outer surface will have many individual flakes taken out of it and maybe a piece of the original outer surface of the rock. The other side will be one smooth "bulb of percussion" with obvious concentric wave marks showing where the shock wave went through it. At the top of the bulb will be a small flat surface where the rock was struck to produce the flake. Large flakes "spalls" were made into tools and arrowheads, smaller flakes are the "debitage" from working the larger flakes. A "biface" is a spall that has been further worked by removing smaller flakes to sharpen it or shape it.
When I got home I broke some obsidian cobbles and one of the - with two whacks - I had a beautiful razor sharp knife blade in about 20 seconds of work!