rebsr52339 The first one I think I hit 0.00047" too high and about 1/8" to the left of where I was aimin. The leftness caused it to intersect with the previous flake scar and dive through the piece at an angle to get the crack started and it just kept going.
The second rock was kinda brittle and had some cracks that I thought I worked out but the snap was actually two cracks that decided to get together all of a sudden when I struck right next to the one near the base.
NonBacked both rocks where raw. The first one was grainy and heat may have made it more knappable but the second one was brittle and I think heat would make it more so.
I like to work raw rock with direct percussion. Shiney rocks and indirect percussion are not things I do very often.
Hawkdancer That might work. I'll stand way back and just throw the bopper at it.