Emery

Emery, an impure variety of corundum (q.v.) or sapphire, containing 60 to 80 per cent. of alumina and 8 to 33 per cent. of iron-oxide. It is grey or brown, sub-opaque and amorphous, with a hardness of 9 and specific gravity of 3-7 to 4-3. It occurs in schists, gneiss, and metamorphosed limestone, and in large boulders in a red soil, in Naxos and other islands in the Grecian Archipelago, and at several localities in Asia Minor, whence in all from 5,000 to 7,000 tons are obtained annually. It is packed in casks containing 4 to 5 cwts. each. After being crushed and sifted, it is either concreted into grinding wheels or hones, or stuck on to paper or cloth, and is used for polishing plate-glass, crystals, and metals, and for cutting granites. Emerywheels are made up of a mixture of emery-powder and vulcanised indiarubber; they are used extensively for smoothing and polishing iron-castings and for sharpening tools.