I happened to stumble across a few nice pieces of slate. Being ever curious, I rubbed a spoon on one & it left quite a scratch pattern on the stainless steel. So I lapped a few of them just for grins.

As expected, every rock is different, but they are all surprisingly good for knife sharpening! Much too coarse for razors (except maybe for the coarsest of bevel-setting), but fine for kitchen and pocket knives.

So I bought a diamond abrasive hacksaw blade at the hardware store for $7 and went into the small independent manufacture of genuine Massachusetts slate hones My GF has a nice 2" x 12" x 1" slab on her counter top now, next to her kitchen knives, & I'm working on sawing another slab off the same chunk.

It's kind of fun to see what personality each stone is going to have. My best one is a light gray piece with brown & black swirlies in it (no idea what the inclusions are). It's a small piece, suitable mainly for pocket knives. I have another one about the same size that's nearly black. It's coarser & more aggressive.

I will never be able to look at a rock the same way again, and now neither will you