a hard gary-black mineral consisting of corundum and either hematite or magnetite; used as an abrasive (especially as a coating on paper)
a very hard mineral that is used for polishing things and making them smooth (émeri, from smiriglio, from smyris). Granular rock consisting of a mixture of the mineral corundum (aluminum oxide, Al2O3) and iron oxides such as magnetite (Fe3O4) or hematite (Fe2O3). It is a dark, dense substance that looks much like iron ore. Turkey is the world's major producer. Long used as an abrasive or polishing material, particularly in sandpapers, it has largely been replaced by synthetic materials such as alumina. Its largest application now is as a nonskid material in floors, stair treads, and pavements
Corundum in the form of grains or powder, used in the arts for grinding and polishing hard substances