In D.C. Waldorf's book "The Art of Flintknapping", he has a list of lithic resources that he rates on a scale of 1 through 5 (page 13). He says this scale is based on Callahan's scale (Callahan 1979:16) where glass is a 1 and rhyolite is a 5. Since my scale is reversed and goes from 0 through 10, I have expanded Waldorf's scale to compare it with mine.
Waldorf uses the term "workability" rather than "knappability".
He places many of the materials much lower or higher than I would, which means that my scale (when I add the names of the materials) will be very different. I will take his ratings into account, though.
Note: "HT" means Heat Treated.