The Probert Encyclopaedia of Rocks & Minerals

EMERY

Emery is an impure fine-grained form of corundum (aluminium oxide) of blackish or bluish-grey colour, chiefly found in shapeless masses and mixed with other minerals.in conjunction with iron oxides and spinel. Emery is very hard; is infusible, and is not attacked by acids; has the formulae Al2O3 employed widely as an abrasive: it is employed in cutting and polishing precious stones; in smoothing the surface of the finer kinds of lenses preparatory to their being polished; in the polishing of marble; by cutlers, locksmiths, glaziers, and other artisans. For all these purposes it is pulverized in large iron mortars or in steel mills, and the powder, which is rough and sharp, is carefully washed and sifted into eight or ten different degrees of fineness. Emery-paper and emery-cloth are made by laying a thin coat of glue upon the fabric, and dusting the emery from a sieve of the required size. Typically emery consists of 60 percent corundum and 40 percent iron oxide in the form of magnetite.
Research Emery