as a Branch of Natural History, c^r. 



269 



mamillary and botryoidal groups, and in cleavable masses. More rarely, mo- 

 lecular individuals are assembled in compact masses. 



Second example taken from the family Pyrites, of the order Pjrrites, in the 

 class Metallophanous Crystals. 



Genus. Sulphuret op cobalt, or grey cobalt-ore. 



Comprising the Glanz kobali and Weisser speiss kobalt of Werner ; the Cobalt 

 ffris and Cobalt arsenical blanc argentin of Haiiy ; the Octahedral cobalt-pyrites^ 

 and the Ilexahedral cobalt-pyrites or Silver-white cobalt of Mohs and Jameson ; 

 the Schwefel kobalt or sulphuret of cobalt of Berzelius, and the Kobalt kies of 

 Hausmann. 



N. B. The Grauer speiss kobalt of Werner, and the Cobalt arsenical fond of 

 Hauy, belong to the family Arsenideous, of the order Alloys. 



Chemical Nature — Sulphuret of cobalt combined Avith sulphurets of iron 

 and copper, and with arseniurets of cobalt and ii'on. These various combina- 

 tions which change neither the colour nor the primitive form of the sulphuret 

 of cobalt, but are distinguished by some peculiar characters, occasion a division 

 of this genus into three subgenera, for each of which will be given the analy- 

 ses and the mineralogical signs belonging to it. 



CHARACTERS COMMON TO THE THREE SUBGENERA.* 



Primitive form, the cube ; colour, tin or silver-white ; lustre, splendent and 

 specular. Spec. grav. 6 to 6.6. Scratch apatite, scratched by feldspar. Give 

 often sparks when struck by steeL With the blowpipe, give a blue colour 

 to borax. 



I. Subgenus. CoBAtT-rYRiXES. 



Kobalt kies J Hausmann. Schwefel kobalt^ or sulphuret of cobalt, Berzelius. 



Giving no fumes nor smell of garlic with the blowpipe. 



Sulphuret of cobalt predominating, and combined with a small proportion 

 of sulphurets of copper and of iron. 



Berzelius's formula of the sulphuret of cobalt of Bastnaes, Fe S^ + 4 Cu S 

 + 12 Co S3. 



Analyses of the sulphuret of cobalt 



100,00 



0,9497 



. • The character* of the fiunUy, the order, and the class, already given above, are not repeated 

 here. 



\ Afh. y Tyr. Ui. 316, and Ann. de Chim. t. 83, p. 329. X Ann. des Mines, x. pp. 3, i. 



