On the main page, it's mentioned that go-gamestore.com sells marble stones, and Yutopian used to. Yutopian no longer sells them and go-gamestore.com has them heavily discounted.

Has anyone used these stones? Were they removed from Yutopian and discounted on go-gamestore.com for a reason? Do they chip, for instance, or scratch the goban? Or are they simply not big sellers because people are suspicious of them for no good reason?

I already have some decent bi-convex yunzi stones, but I'm in the market for a set of single convex stones, and if marble stones are nice, I may grab a set at go-gamestore since the price is so low.