4 96 COBALT. 2. Flat octahedron, which is either perfect, or is more or less deeply truncated on all the angles. The external surface ot the crystal is smooth and splendent, and the lustre is metallic. Internally it is glistening, and the lustre is metallic. The fracture is coarse and fine grained uneven, seldom scopiform and stellular fibrous, and radiated. The fragments are indeterminate angular, rather sharp- edged ; in the varieties with a radiated fracture, wedge- shaped. It occurs in coarse, small and fine granular distinct concretions ; sometimes also in lamellar fortification-wise bent concretions. It is semihard in a high degree. It becomes shining in the streak. It is brittle. It is easily frangible. It is uncommonly heavy. Specific gravity, 7.379,-7.751, Karsltn; 6.2173, Kopp. Chemical Characters. Before the blowpipe it gives out a copious arsenical va pour on the first impression of the heat; it melts only partially, and that with great difficulty, and is not at tractable by the magnet; on the addition of borax it im mediately melts into a grey metallic globule, colouring the borax of a deep blue. It is considered to be a compound of cobalt, iron and arsenic. Geognostic Situation. It occurs in veins in granite, gneiss, mica-slate, and clay-slate; seldomer in transition clay-slate and lime stone;