ORDER v. PRISMATIC COBALT-MICA. 187 



mer of these contains the more perfectly formed varieties, 

 which appear as crystals, as micaceous scales, aggregated 

 into globular masses, or crystalline coats, as long as the in- 

 dividuals are still recognisable. When they cease to be 

 observable, the second sub-species is formed, which consists 

 of a peachblossom-red powder, either coating pther mine- 

 rals, or mixed up with, and imparting to them, an extrane- 

 ous colour. The black, brown, and yellow Cobalt-Ochre 

 do not stand in any natural-historical relation with the pre- 

 sent species. 



2. The chemical composition has been found by BUCHOLZ 

 to be, 



Oxide of Cobalt 39-00. 

 Arsenic Acid 37-00. 

 Water 22-00. 



Its chemical formula is Co 3 As 2 +12 Aq, and the correspond- 

 ing ratio of its ingredients, 39-95 oxide of cobalt, 40-90 ar- 

 senic acid, and 19-J5 water. Alone before the blowpipe 

 it assumes a darker colour. Upon charcoal it emits copious 

 arsenical fumes, and melts in the inner flame into a bead 

 of arseniuret of cobalt. With borax and other fluxes it 

 yields a fine blue coloured glass. 



3. It occurs in veins traversing rocks of various ages, 

 and also in beds. It is accompanied by various minerals, 

 as Nickel- and Cobalt-pyrites, octahedral Bismuth, several 

 species of the orders Malachite and Glance, also by ochrey 

 varieties of prismatic Iron-ore, and particularly by rhombo- 

 hedral Quartz, prismatic Hal-baryte, and rhombohedral 

 Lime-haloide. 



4. The principal localities of this species are, Schneeberg 

 and Annaberg in Saxony, and Flatten in Bohemia, where 

 it occurs in veins in primitive rocks ; Saalfeld in Thuringia, 

 Riegelsdorf and Bieber in Hessia, where it is found in 

 veins in secondary mountains. It is besides found in 

 Wiirtemberg, in the district of Siegen in Prussia, in the 

 Tyrol, in Norway and in Sweden. It is met with also in 

 several places in England and in Scotland. 



