Cobalt minerals

Cobalt minerals are mainly sulfides, but some are also arsenides. Data for important minerals are collected in Table 30.1. 

Mineral Formula Color/Luster streak Hardness Mohs Density g/cm  

Linnaeite Cobalt sulfide (Co, NiljS Gray to white. Metallic Black 4.5-5.S 4.8 

Skutterudite Cobalt arsenide (Ni, Co) As 3 White to silver. Metallic Black 6 6.5 6.8 

Most cobalt is obtained as a by-product of copper-nickel mining and refining. The nickel content in ores can be 1.5% while the cobalt content is 0.15%. 

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Cobalt is the thirtieth most abundant element on earth and comprises approximately 0.0025% of the earth s cmst (3). It occurs in mineral form as arsenides, sulfides, and oxides trace amounts are also found in other minerals of nickel and iron as substitute ions (4). Cobalt minerals are commonly associated with ores of nickel, iron, silver, bismuth, copper, manganese, antimony, and 2iac. Table 1 Hsts the principal cobalt minerals and some corresponding properties. A complete listing of cobalt minerals is given ia Reference 4. 

Table 1. Important Cobalt Minerals and Corresponding Properties ...

In Zambia, having a production second only to Zaire, cobalt is mined by Nchanga ConsoHdated Copper Mines Ltd. (NCOM) and Roan Consohdated Ltd. (ROM). The cobalt minerals found there include minnaeite, carroUite, and cobaltiferrous pyrite. 

Main opaque minerals are chalcopyrite, pyrite, pyrrhotite, sphalerite and bornite (Table 2.22). These minerals commonly occur in massive, banded and disseminated ores and are usually metamorphosed. Hematite occurs in red chert which is composed of fine grained hematite and aluminosilicates (chlorite, stilpnomelane, amphibole, quartz) and carbonates. The massive sulfide ore bodies are overlain by a thin layer of red ferruginous rock in the Okuki (Watanabe et al., 1970). Minor opaque minerals are cobalt minerals (cobaltite, cobalt pentlandite, cobalt mackinawite, carrollite), tetrahedrite-tennantite, native gold, native silver, chalcocite, acanthite, hessite, silver-rich electrum, cubanite, valleriite , and mawsonite or stannoidite (Table 2.22). 

These ores also contain cobalt minerals, mainly carrollite (C0CUSO4) and cobaltite (CoAsS). 

Copper oxide mixed ore - Type 1. The main copper minerals found in these ores include malachite, pseudo-malachite, chrysocolla and some tenorite. These ores also may contain mainly siliceous gangue minerals, including spherocobaltite as the main cobalt minerals. The carbonaceous types also contain an appreciable amount of clay slime minerals. 

Mixed copper sulphide oxide ores. These contain varieties of both sulphide and oxide minerals, and are the most complex copper-bearing ores from a beneficiation point of view. The major copper minerals present in this ore type include bomite, chalcocite, covellite, malachite, cuprite and chrysocolla. In some cases, significant amounts of cobalt minerals are also present in this ore. 

The fatty-acid-based collectors have been employed for the past 60 years for flotation of oxide copper/cobalt minerals from Congo, a company formerly owned by Union Minera (Belgium). 

An appreciable amount of the cobalt in these ores is represented by sulphide cobalt minerals, mainly carrolite. 

Marcoux, E., Moelo, Y., Leistel, J.M. 1996. Bismuth and cobalt minerals as indicators of stringer zones to massive sulphide deposits, Iberian Pyrite Belt. Mineralium Deposita, 31, 1-26. 

Cobalt has been in use as a coloring agent for glass since ancient times. The metal was isolated by Brandt in 1735 and confirmed as an element by Bergman in 1780. Cobalt is widely distributed in nature, but in small concentrations. Its concentration in the earth s crust is estimated to be about 0.0025% and in the sea water is about 0.02 pg/L. Cobalt minerals with their chemical formula and CAS Registry numbers are tabulated below ... 

Shortly before this, Georg Brandt had discovered a new cobalt mineral at die Goran Mine at Bastnas, near Riddarhytta. "My curiosity, said he, did not allow me to postpone the chemical investigation until... 

TABLE I. PRINCIPAL ECONOMICALLY IMPORTANT COBALT MINERALS... 

Additionally, the L. innocua ferritin-like protein served as a template for the controlled mineralization of two cobalt oxide phases Co(0)OH and C03O4 under two reaction temperatures of 23° and 65 °C, respectively. Substantial differences in crystallinity of the cobalt mineral core was observed between the two synthetic routes. The mineralization reaction carried out at higher temperatures yielded more crystalline nanomaterials, while the low-temperature synthesis tended toward amorphous material. The high crystallinity obtained at higher temperatures is most likely due to removal of structural waters present in the protein cavity and the surpassed energy barrier of nucleation at 65 °C. ... 

Besshi deposits comprise thin sheets of massive, well-layered pyrrhotite - - chalcopyrite + sphalerite - - pyrite with minor galena and cobalt minerals interlayered with terrigenous clastic sedimentary rocks and calc-alkaline... 

Cobalt dyes have been used for centuries. Craftsmen used materials from the earth to color glass, pottery, glazes, and other materials. Cobalt minerals were especially prized for their rich blue color. 

But cobalt miners were confused too. Some ores of nickel also look like cobalt ores. But these ores did not react chemically in the same way either. Cobalt mine owners called the misbehaving ores of nickel cobalt which had lost its soul. ... 

Unlike its neighbors in the Periodic Table, iron, nickel, and copper, cobalt is not widespread in nature. It has an average abxmdance in Earth s crust of 2 5 parts per million (ppm) in ultrabasic rocks, where cobalt is most common, the average concentration is 110 ppm. Cobalt minerals may be concentrated by a range of geological processes to produce workable ores that typically contain 1,000-2,000 ppm. 

Thirty-four cobalt minerals have been recognized, principally sulphides, selenides, arsenides, sulfarsenides, carbonates, sulfates, and arsenates. The main ore minerals are the sulfides linnaeite, carrolite, and cobaltiferous pyrite the arsenides skutterudite and safllorite the sulfosalt cobaltite and the oxides asbolite (cobalt wad) and erythrite. 

Cobalt always occurs in Nature in association with nickel and usually also with arsenic. The most important cobalt minerals are smaltite, CoAs2, and cobaltite, CoAsS, but the chief technical sources of cobalt are residues called speisses, which are obtained in the smelting of arsenical ores of nickel, copper and lead. The separation of the pure metal is somewhat complicated and of no special relevance here. 

Llorca S. and Monchoux P., Supergene cobalt minerals from New Caledonia (Canadian Mineralogist, Vol.29, 1991), 149-161... 

Discovery Cobalt minerals were used in antiquity to give blue coloring to glass and pottery. The Swedish chemist Georg Brandt (1694-1768) investigated the color cobalts and found a new element that he named cobalt. He was also the first to isolate cobalt in the metallic state in 1735. 

Table 30.1 Important cobalt minerals and their properties...

Synthetically related analogues such as cobalt arsenate (q.v.) have been used in a pigment context. No specific examples of the use of this mineral are currently known however, Miihlethaler and Thissen (1993) point out that in addition to the main cobalt mineral smaltite, erythrite (and cobaltite) were probably used in the manufacture of smalt (qq.v.) in the seventeenth and eighteenth centuries. 

Cobalt occurs as a constituent of various minerals found in many parts of the world. Cobalt ore was heated to form an oxide which was then mixed with silica cpiartz sand and sold under the name saffer (also, saffre or zaflre ) to glassmakers. The principal source of cohalt historically was the mineral skutterudite ((Co,Ni)As3 j named after its locality Skutterud, Norway this mineral was also known historically as smaltite (q.v.) in reference to its use for smalt). Deposits in Saxony were, for centuries, the main supply of European cobalt however, there are sources in France and Spain. The related cobalt minerals erythrite (q.v.) and cobaltite were probably also used in the seventeenth and eighteenth centuries (Muhlethaler and Thissen, 1993). 

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