Corundum is a mineral from the category of oxides and hydroxides and is the most frequently used industrial mineral worldwide. It also occurs naturally as a gemstone (sapphire, emerald, ruby). Chemically corundum is aluminium oxide with the chemical formula Al2O3.
Commonly referred to as “grit”, this number designation is determined by the amount of abrasive mineral that can pass through a mesh screen with specific size openings. Therefore, a 40 grit abrasive particle will pass through a mesh