i found two colored pumice stones in a sandy area outside of Castle Rock, WA. They are black and white. There was also one red one, but it was a little heavier and not quite as porous too. But the red one is not as numerous as the black and white pumice stones.
I noticed that the black ones tend to be a little heavier than the white ones for about the same sizes. This is going on how it feels in my hands. They seemed to have about the same coarseness. I’m guessing that the black ones are more likely to sink sooner than the white ones. What makes the pumice black? It’s a different material of stone involved.
White is supposed to be the more common pumice color, we know that because that is the only color we see sold commercially. Does the black pumice stone have no value? You would think people would want to use black more, because their calloused skin would show better on a black one. Then they could know how often the pumice should be cleaned.
I am a little concerned that black isn’t equally sold along with white pumice. I believe there is probably a lot of black stone available as well, but it has gotten an unfair stigma. Or maybe the black has arsenic and is dangerous to use. I’m no rock expert.