I agree with Cowboy. Take that rock to someone who sells rock to knappers, if it doesn't have fracture lines, you can trade it for a lot of lower grade knappable rock or you need to get it slabbed. If the guy you got the rock from has a saw, you may want to get the saw. Usually, the guy with the saw gets 1/2 the rock he saws up. Or you could pay money to get it sawn. Bill