Obsidian is an incredible rock! When molten lava cools too rapidly for the rock to form crystals-it creates a 'volcanic glass.' Usually, gray to black, it can have brownish red streaks, or go from opaque to translucent. In the US, it is found in spots from the Rocky Mountains to the west coast, basically anywhere there has been volcanic activity in the past. Early man prized this stone for its beauty, workability, and the fact that it fractured to an extremely sharp edge. Brigham Young University, in Utah, did some comparitive studies between a surgical steel blade, and an obsidian blade, using the electron microscope. They found that obsidian was 500 times sharper than the surgical steel, fracturing down to almost the last molecule. People are fascinated, at flintknapping demonstrations, when I strike off a sharp flake and proceed to shave the hair off my arm. Being right handed, I don't trust my ability to safely shave with the left hand...so I usually end up with one bald arm and one hairy arm....lol.