I have an unknown natural stone I bought in a local shop years ago that I'm just now getting around to lapping. I don't know much about it except that it was supposedly mined locally in the Mountains of NC. I lap on wet/dry sandpaper on a marble slab. I started with 400 grit thinking that it looked pretty smooth and after I cleaned it up some with that I saw the chatter looking marks and small pits and the corner that is lower then the rest of the stone. I went back to the 220 grit and it is taking what seems like forever to lap this stone into true. Thats all I really had to say. I don't know if I'll see them before I get done but do any of you have any suggestions for lapping with wet/dry sandpaper? Also is there a way to know what kind of stone this is? I posted a picture once and Glen said it may be a hard dense Arkansas stone but it seemed to soak up water so it might not be. It is much harder and finer then I thought with a very glass like feel after I had some smoothed with the 400 grit. It takes awhile to create a slurry and its hardly removing any material with either grit of sandpaper.