"Rock Tumbler grit", also known as "rock polishing grit", is a silicon carbide powder that is much harder than the types of rocks that are commonly polished inside a rock tumbler. If it is tumbled inside of a barrel with rocks and water the abrasion caused from the grit particles https://waylonghhfg.theideasblog.com/29383172/the-smart-trick-of-silicon-carbide-defects-that-no-one-is-discussing