606 MANUAL OF NATURAL HISTORY. 



2, H. = 2-2*5, white, brittle, soluble, formed 

 by the decomposition of Zinc blende. Zinc 

 compounds form a clear glass with borax ; 

 with soda or charcoal, they give a bluish 

 flame; with cobalt solution, a green colour. 

 Symb. Zn. 



7. Family. — Cadmiides. Minerals containing com- 



pounds of Cadmium, I, as Sulphur et or 

 " Greenockite/' hexagonal, sp. gr. 4-8, H =3-3*5, 

 yellowish, nearly transparent, rare, in por- 

 phyrinic trap ; 2, as Oxide, with many ores of 

 zinc. Compounds of Cadmium, when heated 

 on charcoal, deposit a reddish-brown powder. 

 Symb. Cd. 



8. Family. — Nickelides. Minerals containing com- 



pounds of Nickel. Occur 1, as Sulphur et or 

 "Millerite," rhombohedral, sp. gr. 5-4, H. 

 = 3-3*5, brass-yellow, brittle ; 2, as Arseni- 

 uret or "Arsenical-Nickel/' hexagonal, me- 

 tallic, sp. gr. 7-4, H. = 5-5*5, reddish, brittle, 

 with various metallic ores; 3, as A rseniate 

 or " Nickel-Ochre/' pulverulent, soft, apple- 

 green, with Copper-Nickel ; 4, with Sulphur 

 and Arsenic, as " Nickel-glance/' hemihe- 

 dral, compact or lamellar, sp. gr. 6, H. = 5-5, 

 whitish, with galena, quartz, &c. ; 5, with 

 Sulphur and Bismuth, or " Bismuth-Nickel/' 

 in octohedrons and cubes, sp. gr. 5, H. = 4-5, 

 grayish, brittle, with quartz and copper py- 

 rites. Oxide of Nickel forms a clear, yel- 

 lowish glass with borax, becoming blue on 



