454 PHYSIOGRAPHY. CLASS II. 



Its chemical formula is Co As 3 or Go As 2 + Co As 4 , cor- 

 responding to 22-30 of cobalt and 77*70 of arsenic. Before 

 the blowpipe it emits copious fumes and odour of arsenic. 

 It melts into a white brittle metallic globule. To borax 

 and other fluxes it imparts a blue colour. It affords a 

 pink solution with nitric acid, leaving a white residue, 

 which is itself dissolved on farther digestion. 



2. Octahedral Cobalt-pyrites is principally met with in 

 veins, traversing rocks of various ages, more rarely in beds. 

 It is accompanied by ores of silver, or by ores of copper, 

 and along with the first sometimes by octahedral Bismuth 

 and prismatic Cobalt-mica. In beds it is associated with 

 Arsenical-pyrites and Lime-haloides, and rarely it is found 

 without the prismatic Nickel-pyrites. 



3. In veins traversing primitive rocks it occurs at Schnee- 

 berg and Annaberg in Saxony ; also at Freiberg and Ma- 

 rienberg ; likewise at Joachimsthal in Bohemia, and in veins 

 in killas at Wheal Sparnon in Cornwall. The veins of the 

 counties of Sayn and Siegen, which contain it, are included 

 in greywacke, and those of Thuringia and Mansfeld, and 

 of Biechelsdorf in Hessia, in cupriferous shale. It occurs 

 in beds at Schladming in Stiria, at Orawitza in the Bannat, 

 and at Dobschau in Hungary. It has also been quoted 

 from Piedmont and several other countries. 



4. It is a valuable mineral for the preparation of blue 

 enamel colours, but particularly for smalt, and forms 

 an important object in some of the mining districts of 

 Saxony. 



5. The Grey Cobalt-Ore (JAM. Syst. Vol. III. p. 287), 

 which is considered by HAUY as a variety of the present 

 species, and the Radiated White Colalt (Id. ibid. p. 286), will 

 probably require in future to be established into a separate 

 species. They are, however, too imperfectly known at pre- 

 sent to enable us to determine their place in the order Py- 

 rites. From several imitative shapes in which it occurs, 

 the regular forms of this species seem to belong to the 

 prismatic system, among which are very thin four-sided 



