"Rock tumbler grit", also known as "rock polishing grit", can be a silicon carbide powder that is much harder than the types of rocks that are commonly polished within a rock tumbler. If it is tumbled in a barrel with rocks and water the abrasion caused because of the grit https://siliconcarbideproducts37036.nizarblog.com/29081064/3-physical-properties-of-silicon-carbide-secrets