Smaltite, Cobaltite & Sperrylite Composition, Crystallization and Structure
Smaltite - Chloanthite
Smaoltite is cobalt arsenide, CoAs2, cloanthite, nickel arsenide, NiAs2. the two molecules are isomorphous and all gradation between the two species occurs. Isometric; pyritohedral. Usually massive, granular. Octahedral cleavage. H. = 5.5-6. = 6.3 – 6.8. Metallic luster. Color white. Streak black. Fusible at 2-2.5. Roasted on charcoal give a volatile coating of arseniuos oxide with characteris tic garlic odor. In borax bead in O. F. give blue color (cobal). Rare species, occurring with other cobalt and nickel minerals, often associated with silver and copper ores.
Cobalite is a sulpharsenide of cobalt, CoAsS; gersdorffite a sulpharsenide of nickel, NiAsS. The two molecules are isomorphous with each other and may occurs together in varying amounts. Usually, however, any specimen will be found to be near one or the other ends of the series. Iron is frequently present, replacing the cobalt or the nickel, and sometimes in considerable amount. Isometric; piritohedral. Cobaltite commonly in cubes, pyritohedrons and octahedrons, also massive. Gersdorffite usually massive. Cubic cleavage. H. = 5.8-6. G. = 5.8-6.2. Metallic luster. Color white, in cobalite inclining to reddish tone. Streak black. Fusible 2-3. On charcoal give a volatile white sublimate of arsenious oxide with characteristic garlic odor. In O. T. give volatile crystals line sublimate of arseniuos oxide with odor of sulfur dioxide. In O. F. in borax bead give deep blue color (cobalt); if gersdorflite contains no cobalt, gives brown bead (nickel). Rare minerals, cobaltite being el commoner. Found associated with other cobalt and nickel minerals and with silver and copper ores. Notable occurrences of cobalite are at Tunaberg, Sweden, and Cobalt, Ontario, Canada.
A platinum arsenide, PtAs2. Isometric; pyritohedral. Usually in small grains, or in almost microscopic crystals fragments. H. = 6-7. G. = 10.6. Metallic luster. Tin-white color. Black streak. Fusible at 2. Roasted on charcoal gives volatile white containg of resinous oxide with characteristic garlic odor. Roasted in O. T:, at firs very gently, a platinum sponge is left, which is insoluble in any single aid. A very rare mineral and the only known compound of platinum occurring in nature. Found with chalcopyrite in a gold-quartz vein near Sudbury, Canada, and with covellite at the Rambler Mine, Encampment, Wyoming. Found in large crystals at the Waterberg distritict in the Transvaal, South Africa.