Thread: Stone Identification

I vote slate too. But based solely on the color of the slurry.

I have a natural combo on which the "blue" side is black, or almost black. It is very obviously a natural, with a wavy and strikingly well-defined seam. I thought for a while that coticule must occasionally be found adjacent to something other than BBW, since mine was so damn black. But lapping it yielded the tell-tale blueberry slurry.