EMERY (formerly m•rit', from OF. cmeril, Sp., Port. esmeril, It. suir•iylio, from Gk. criAelpts, sutyris, sun iris, emery). A variety co rundum (q.v.), or of the mineral species of which corundum and sapphire (with Oriental ruby, etc.) are also varieties. It agrees with them very perfectly in hardness and specific gravity, but is dull, opaque, and not crystallized, sometimes of a grayish black, and sometimes of a blue color. It contains chiefly alumina and oxide of iron, but less of the former than does either corundum or sapphire. It may also have small amounts of silica and lime. It occurs both massive and disseminated ; although very com pact, it has a somewhat granular structure. It is found in several parts of Europe, in Asia Minor, Greenland, etc., generally in masses scattered through aqueous deposits, but in one locality in Saxony in beds of steatite in a schistose rock. Most of the emery used in America collies from Turkey, but in the United States it is known to occur at Chester, Mass., and Peekskill, X. Y., while corundum in deposits of economic value is found in North Carolina and Georgia. It is found in lumps, having a granular structure.
It is prepared for use by first breaking it into pieces about the size of a hen's egg, then crush ing these to powder by stamps. It is then sifted to various degrees of fineness, which are numbered according to the meshes of the sieve. Plate-glass manufacturers and others separate emery powder into different degrees of fineness by the method of elntriation (q.v.). A number of copper cylinders of graduated capacities are placed in a row, and filled with water; the emery, churned up with an abundance of water, is ad mitted by a pipe into the smallest; it then passes to the next in size, and finally flows from the largest; and thus, as a given quantity of water with emery suspended in it passes in equal times through vessels of varying capacities, the amount of agitation will obviously be greatest in the smallest vessel, least in the largest, and in like proportion with the intermediate; the largest particles, therefore, sink in the smallest vessel, and so on till only the very finest will reach the largest vessel. In this manner any number of
gradations of fineness may be obtained, accord ing to the number of sizes of the vessels. Du triation in oil or gum-water is sometimes used on a smaller scale, the emery being stirred up in the liquid, and portions poured off at different intervals of time, the finest being of course the last to settle. The use of the oil or gum is to make the subsidence take place more slowly.
Emery thus prepared is used for a great many important purposes in the arts. Being next in hardenss to diamond-dust and crystalline corun the lapidary uses it for cutting and polish ing many kinds of stone. Glass stoppers of all kinds are ground into their fittings with it. Plate glass is ground flat by its means: it is also used in glass-cutting, and in grinding some kinds of metallic fittings. When employed for the polishing of metals, it has to be spread on some kind of surface to form a sort of fine file. Emery paper, emery cloth. emery sticks, emery cake, and emery stone are various contrivances for such purposes. Emery paper is made by sifting emery over paper which has been covered with a coating of glue. It is used either by wrapping it round a fine file or a stick, or in the hand, according to the form of the work. Emery cloth is made like emery paper, with coarse calico sub stituted for the paper. The emery does not adhere so well to this as to paper, and it is therefore not used by metal-workers, who work emery paper till smooth with wear, but is chiefly used for purposes where the hand alone is used, and paper would tear. Emery sticks are used for the same purposes as emery paper wrapped round files; they arc made of deal sticks shaped like files, then glued over, and dipped once or twice in a heap of emery. Emery stone is a kind of earthenware mixed with emery, formed by pressing a mixture of clay and emery into suitable molds, and then firing, like common earthenware. It is molded into wheels, laps, etc. Its hardness and cutting power are very considerable. Emery wheels are most efficient; they vary in diameter from 1 to 36 inches. and are revolved at a high velocity. See