Rock Tumbling and Lapidary Supplies
Rock Tumbler Grit - Lapidary Abrasives. Rock tumbling "grit" is a silicon carbide powder with a Mohs hardness of 9.25. That is much harder than the types of rocks that are commonly tumbled. Coarse grit is used to shape the rocks, then progressively finer grits are used to smooth their surface and prepare them for polishing.