This grit is used in STEP 1 of the rock tumbling process in a rotary tumbler. It is an 60/90 mesh silicon carbide granule. In a rotary tumbler we use about two level tablespoons of grit per pound of rock. When tumbling you will place enough rocks in the barrel to make it about 2/3 to 3/4 full. Then, add about two level tablespoons of grit for each pound of rock. Finally, add enough water to almost cover the rock