stone ID

[northpaw]

I picked up a few rocks while walking in the nearby mountains with the intention of lapping them to see what I could see. Two turned out to be duds, but this one is much more interesting.

For starters, it's very, very hard. It's been harder to lap than anything else I have (C12k, barber's hone, etc.). As you might be able to see in the pic, there are no visible grains in the greenish areas - only tiny layer-like lines. The lack of grains is what originally caught my eye.

After getting it flat and smoothing out any edges that could catch a razor, I took an already-sharp razor and did a bunch of passes with a lot of water on the stone. Didn't seem to dull the edge. If anything, it felt sharper on my thumb pad. I noticed that the stone absorbs water fairly quickly, so I started just lightly misting the surface and honing until it was dry (probably 20 passes each time). Felt like it started to build a tiny bit of slurry as it dried.

Shaved with the test blade today and got the best shave I've ever had from that particular razor. One benchmark was that I was able to shave my upper lip against the grain with the spine completely flat on my face. The only other time I've been able to do that consistently is off of my Shapton 30k.

Anyway, I know it could be some kind of fluke, but I'm curious if anyone knows what kind of rock this is. Should I head back up the mountain with a pickup truck?

(click for larger pic)