Hand Tools Archive
I usually see good fineness and good cutting power from stones like that - they have a harder feeling on the surface and a sense of more control than the lilywhite, too.
But that could just be perception.
That stone was glassed on the surface by the seller (lapped to a point that it was reflective with something - I have no idea what, but that's popular for some stone collectors to flatten and completely polish stone surfaces).
I worked a back with it a minute ago while eating lunch, and it's pretty fine. It'll be interesting to see what happens with it after it sees wrought iron on a japanese tool (that usually pulls a few particles loose and really wakes up a stone).
I'll post the scope pictures tomorrow.