MANUAL OF NATURAL HISTORY. 605 



gypsum or salt; 6, as Silicate, 1, "Talc/ 7 

 "Steatite" or "Soapstone," generally in 

 foliated masses, sp. gr. 2 - 7, H. = 1 - 1 -5 , greenish, 

 sectile, greasy, when the texture is somewhat 

 granular, it is " French-chalk ; " 2, " Meers- 

 chaum/' compact, H. = 2-2*5, grayish- white, 

 dry and harsh, in alluvial deposits ; 3, " Ser- 

 pentine/' trimetric, sp. gr. 2'2-2'5, H. = 3-4, 

 greenish, sectile, often forming mountain 

 masses ; 4, combined withlron as " Chrysolite/' 

 trimetric, usually in small transparent grains, 

 sp. gr. 3-3-3-5, H. = 6'5-7, greenish yellow, in 

 basaltic rocks. Magnesian compounds if 

 moistened with solution of nitrate of cobalt, 

 and heated before the blow-pipe, afford a 

 clear rose-red colour. Symb. Mg. 

 6. FAMILY. Zincides. Minerals containing com- 

 pounds of Zinc. Occur 1, as Sulphuret or 

 "Zinc-blende," in rhomboidal -dodecahedrons, 

 sp. gr. 4, H. = 3*5-4, yellowish or brownish, 

 brittle, often with Galena; 2, as Oxide or 

 "Red Zinc Ore/' hexagonal, in lamellar masses 

 or grains, sp. gr. 5 -4, H. = 4-4'5, red, brittle, 

 in iron ore ; 3, Silicate or "Electric-Calamine," 

 trimetric, crystalline, fibrous or stalactitic, 

 sp. gr. 3'4, H. = 4-5-5, whitish, brittle, pyro- 

 electric, with zinc ores ; 4, as Carbonate or 

 " Calamine," rhombohedral, sp. gr. 4-4*4, 

 H. = 5, grayish, brittle, effervescent, in cal- 

 careous rocks; 5, as Sulphate or "White- 

 Vitriol," trimetric, in four-sided prisms, sp. gr. 



