I have this stone that's been sitting in my father's basement for 50+ years. I think it was my grandfathers. It sharpens well enough to barely cut arm hair if I go real easy, light slurry, wet, to almost dry with little pressure. After a chrome oxide strop it is amazingly sharp. I assume my grandfather used it around the turn of the century. Any ideas what it is? Dark grey/almost black in color, under a 30X loupe I can see little"crystals" of white that shine if held up to the light. Laps fairly easily using silicon carbide wet/dry sandpaper. The powder left on the paper is grey and like dust. 7" long, 1 1/2 wide x 1" thick. Top picture wet with slurry, the rest dry. Thanks, Rick