Calamine, a name given to two different ores of zinc, the silicate and the carbonate. The most common ore worked for zinc is the anhydrous carbonate. It occurs crystallized in rhomboidal forms, of vitreous lustre, and a little pearly, of white, yellowish gray, or brown color, semi-transparent or opaque, in forms bo-tryoidal, stalactitic, and reniform, and in crystalline incrustations; hardness 5, specific gravity 4 to 4.45. It contains oxide of zinc 64.81, and carbonic acid 35.19. It dissolves with effervescence in acids, and is also soluble in ammonia moderately heated. It occurs in thick beds and irregular masses, among calcareous rocks of the secondary and metamorphic formations. It is rarely found unmixed with oxide of iron and the silicate of zinc. It is extensively worked for the production of zinc paint at Vieille Montagne, between Liege and Aix-la-Chapelle. In this country it is found associated with hematite iron ores, and also with the sulphuret of lead or galena. It is worked near Bethlehem, Lehigh co., Penn., and in the vicinity of Lancaster. In Dana's " Mineralogy V it is called smithsonite. The hydrous silicate of zinc, also called electric calamine, often accompanies the anhydrous carbonate, and it is usually the two minerals mixed which are designated by the name of calamine.

It occurs in forms similar to those of the carbonate, and in crystals derived from a rhomboidal prism. Its hardness is 4'5, or when crystallized, 5; its specific gravity from 3.16 to 3.49. It dissolves by the aid of heat in sulphuric or muriatic acid, and gelatinizes on cooling. It becomes strongly electric by heat, to which property it owes its name. Its composition is, silica 25.1, oxide of zinc 67.4, and water 7.5. - In pharmacy, the term calamine is applied only to the native carbonate, which has always been employed in an impure state. It is often sold, too, of a spurious quality, consisting principally of sulphate of baryta and carbonate of lime, with mere traces of zinc. It is said that the miners in England recognize two kinds Of calamine: one, which they call brass calamine, is sold to the makers of brass; and the other, baryta calamine, which is, the amorphous sulphate of baryta, is sold to the druggists for native carbonate of zinc. In medical preparations calamine is heated to redness, and reduced to an impalpable powder. By this calcination it is converted into oxide of zinc, mixed with the impurities of the ore. In this state it is called prepared calamine.

It is used as an external application only, sometimes in the form of cerate, but more commonly it is dusted upon ulcerated and excoriated parts, upon which it acts as a mild astringent and ex-siccant. In consequence of the impurities of this article, carbonate of zinc obtained by precipitation is substituted for it in the " United States Pharmacopoeia".