164 DESCRIPTIONS OF MINERALS. 
associated with cobalt in the sulphides and arsenides. The 
ores having a metallic lustre vary in specific gravity from 
6-2 to 7-2; and the color is nearly tin-white or pale steel_ 
gray, inclined to copper-red. ‘The ores without a metallic 
lustre have a clear red or reddish color, and specific gravity 
of nearly 38. Cobalt is often present also in arsenopyrite (or 
mispickel), and sometimes in pyrite. 
‘The ores of nickel are sulphides, arsenides, arseno-sulph- 
ides, and antimono-sulphides, a sulphate, carbonate, silicates, 
arsenate; and the metal is a constituent of several cobalt 
ores, and also often of pyrrhotite (magnetic pyrites). Specific 
gravity between 3 and 8; hardness of one 3, but mostly be- 
tween d5and 6. Those of metallic lustre resemble some cobalt 
ores ; but they do not give a deep blue color with borax. 
Linneeite.—Cobalt Sulphide. Cobalt and Nickel Sulphide. 
Isometric. In octahedron$ and cubo-octahedrons ; also 
massive. Color pale steel-gray, tar ees copper red. Streak 
Ditekish: oray. Eh pron Ga— 
Composition. Co, 5, eek a! Ns a cobalt 5°830=100 ; but 
with part of the cobalt replaced by nickel ; copper some- 
times present. Svegenite is a variety containing 30 to 40 per 
cent. of nickel. B.B. on charcoal vields sulphurous odor 
and a magnetic globule ; often also arsenical fumes. 
Obs. From Sweden, Prussia; Mine la Motte in Missouri 
(Siegenite) ; Mineral Hill in Maryland. Sometimes called 
cobalt pyr ites. 
Millerite.—Nickel Sulphide. Capillary Pyrites. 
Rhombohedral. Usually in capillary or needle-like crys 
tallizations ; sometimes like wool. Also in columnar crusts 
and radiated. Color brass-yellow, inclining to bronze-yellow, 
with often a gray iridescent tarnish. Streak bright. Brittle. 
H.=3-3°5. G.=4-6-5°65. 
Composition. NiS=Sulphur 35:6, nickel 64.4=100. In 
the open tube sulphurous fumes. B.B. on charcoal fuses 
to a globule; and after roasting, gives, with borax and salt of 
phosphorus, a violet bead in O. F., which in R.F. becomes 
eray from reduced metallic nickel. 

