@ J. Dempler: Any kind of rock or material is fine. Ideally, they would be made from the correct material, but with different regional styles there's no way for everyone to have access to rock from all parts of the country.
@ Dana: Dana, I think beveling is just an easy, efficient way to sharpen tools, plus, it doesn't use up as much material with each resharpening as it would to flake each edge from both sides. A lot of the Early/mid Archaic points show beveling: Daltons, Thebes, Lost Lake, Bolen, Dovetails, etc.