EMERY, a mineral substance long regarded as an ore of iron, but which appears to be a mixture of corundum and oxide of iron. Emery, reduced to a fine powder by grinding and churning, is very extensively used for polishing metals, glass, marble, and other hard bodies. It is imported into this country chiefly from the Isle of Naxos, where it exists in great quantities; and it also occurs in Germany, Italy, Spain, and in some other parts of the world. It is found in beds in strata of mica slate, and in colour is intermediate between grayish-black and bluish-gray. Specific gravity about 4.000. It varies considerably in quality. The constituents of good emery have been given as follows:—alumina, 80; silica, 3; iron, 4. The great hardness of emery constitutes its value as a material for polishing. Ground emery is used in various ways; as, for instance, applied with glue to paper, cloth, or wood, to be used in rubbing; or formed into paste as an artificial stone for grinding-wheels, &c.