I live in an area that is covered with a lot of shale and slate. My methods are fairly barbaric, I hit the rock with a large hammer and break a piece off, I examine the broken piece, it needs a little bit of sparkle but no crystals larger than a sparkle, fine grain and no voids. If it has all of that and isn't too hard to break a piece off I take it home and cut it. Thats the easy part. Then it needs to be lapped. I lap by hand because a wet sander is expensive and not justifiable at this point. I lap on three progressions of DMT plates. I have discovered that lapping is everything. If the rock isn't flat and smooth you will never know what it really can do. There is also novaculite which is used for making hones. I haven't found any that I know of. My geology knowledge is very rudimentary. Happy rockhounding!