436 ZINC. Geognostic Situation. It occurs in veins in gneiss, seldomer in grey-wacke. t is generally accompanied with copper-pyrites, arsenical- Pyrites, iron pyrites, magnetic ironstone, red silver-ore, white silver-ore, and galena. It is rarely associated with brown blende. Its accompanying vein-stones are calca reous-spar, brown-spar, and rarely asbestous actynolite, and garnet. Geographic Situation. It occurs in Sweden, Saxony, Hungary, and Transyl vania. Uses of the Species. This ore is valued on account of the zinc which it af fords. In order to obtain that metal from it, it is first roasted, to drive off the sulphur, and then ground with charcoal, and exposed to heat in a crucible, when the me tal is reduced, and sublimes into a lute, so placed as to convey it into w'ater, when it condenses in small drops. Observations on the Species. I ■ It is distinguished from Tinstone, by its inferior ardness . from Galena or L.ead-Glance, by its grey-co- oured dull streak ; and it is distinguished from most other su stances which it resembles, by exhaling a sulphureous odour, when either triturated in a mortar, or thrown into an acid. 2. Of all the subspecies, the brown is the most frequent and abundant. 3. It is named Black Jack by the miners in F.ngland ; and is also known under the name Pseudo salena. O ORDER IX