Emery

Emery, naturally occurring impure form of corundum containing iron oxides and other minerals. It has long been used as an abrasive. A layer of finely ground emery is coated onto grinding wheels, paper, or cloth. Though synthetic abrasives have replaced it in many applications, it is still used to polish precious stones and in the manufacture of lenses, prisms, and optical equipment. The major source of emery is the island of Naxos in the Aegean Sea.