That's an interesting question. The honing blades for our knife sharpeners (a Lansky, not that nasty round kitchen thing that came with our knives) has some stones that appear to be like marble. A couple of the stones look rougher and grittier. We pick the stone to match the dullness (coarsest first, smoothest last). Something else for me to research. I wonder if there is a spec sheet for it somewhere.