

COBALT ORES. 43 



igneous rocks. If antimony sulphide is heated in a glass 

 tube closed at one end, a sublimate, black when hot, red- 

 dish-brown when cold, is formed near the test-piece. 



BISMUTH. 



Found chiefly in the native state, but also in combina- 

 tion with sulphur, oxygen, tellurium, carbonic acid, &c. It 

 yields a yellow incrustation in the O.F. of the blowpipe. 



The oxide, sulphide, arsenide, combined sometimes with 

 copper, lead, &c., vary in colour, hardness, and specific 

 gravity. Bismuth glance, containing 81 per cent, of the 

 metal, is usually of a lead-grey colour. When heated in a 

 closed tube yields a sulphur sublimate. On charcoal before 

 the B.F. sputters and deposits a yellow incrustation leaving 

 metallic bismuth. Oxide and carbonate of bismuth (gene- 

 rally of a yellowish, though sometimes grey, greenish white, 

 &c.) is often found at the surface of a bismuth-bearing 

 lode. In Wales and elsewhere bismuth sulphide is soina- 

 tirnes found in gold-bearing ore. 



CHROMIUM. 



The oxide is chiefly found with iron, as chrome iron. 

 Colour brownish black. 

 Lustre submetallic. 

 H. 5-5 ; S.G. 4-5. 



Before the B.F. yields a green bead with borax. 

 Chromate of lead is rarely found. Occasionally an emerald 

 green incrustation is found on chrome iron ore. 



Chrome ochre is of a yellowish green colour. Chrome 

 iron is frequently found in a serpentine-rock country. 



Chromium compounds are often associated with nickel 

 and cobalt ores. 



COBALT. 



Compounds of cobalt, when heated on charcoal before 

 the B.F., yield whitish metallic spangles, which can be 

 attracted by a magnet. The metal moistened on paper 

 with nitric acid gives a red solution, which with hydro- 

 chloric acid affords a green stain on drying. 



Treated with borax in either B.F. it yields a deep blue 

 bead. Before testing, metallic compounds should be roasted, 

 to drive off volatile matter. 



