bjorg
These are raw rock. The material has good knappabilty though and good tensile strength in that it wont just break in two very easily.
I have been heating some gravel slabs to make them pressure flake easier but they come out all over the place from heated too much to not enough heat due to so much variation of lithic grades in gravel.
After years of knapping mostly gravel I've learned to recognize the signs that a piece may be a good one with a very low success rate of it actually being a good knappable rock though.
