Tweeds, I,m from Waterfrd,Pa. an I have a pc of rock that is simular to yours an I took off a flake an wasn't to impressed with mine. I believe it is a very poor grade of flint that I have but I don't know enough about raw stone to really have much of an opinion. I,ve bought most of my rock because I can't find any in our area. There is a man in Girard that I would say is a pro at Knapping maybe He could help you, His name is Mike Santiago. Wish I could help you an scouts with more info. Later Bob