That will depend on what you already know and what you are able to learn. I am not educated in geology and really have little understanding of anything more than the basics. I use what I call a brute force attack. I go out and look for likely spots in the areas that I outdoor a lot and break a few rocks. It is amazing on how the inside often has little resemblance to the outside. I look at the grains on the inside, they give me clues as to whether or not it is worth dragging it home or not. Inclusions are a no go. Non uniform grit is also a no go. I nice solid piece with no cracks and no inclusions works pretty good. I take them home and cut them and lap then and do scratch pattern tests on hard steel. Most often I start with a nice wide and flat chisel. I am looking for cut speed as well as a fine scratch pattern. Although not all hones need to be fast, some can be just smooth. I have found several small deposits that have produced some nice hones. Keep looking or start looking, but let the hunt go on!