Buddy of mine in his 60's told me slate makes a good "find your own" sharpening stone. Locally, our slate is loaded with garnet and layered. Not too hard to "carefully" bust some layers and get a flat surface at desired size whether pocket or benchtop. Anyone have some experience with "found" sharpening stones, especially slate? Have a couple cheapo knives I'm willing to sacrifice to experiment. Anyone who pipes in, please give some idea of your area so anyone from there can benefit. I'm in the Black Hills of South Dakota. Thanks in advance for your input!