Non- Metallic abrasives include natural and synthetic materials, silica sand, flint, olivine, and staurolite, garnet, calcium carbonate, and vegetable products such as walnut shells and corn cobs are all type of natural abrasives. Historically, natural abrasives were available before the development of synthetic abrasives, which include iron silicates, aluminium silicates, calcium silicates, aluminium oxide, sintered or calcined bauxite, glass beads, and plastics.