Cobalt Ores

natural mineral formations containing cobalt in quantities such that extraction is economically feasible. More than 100 cobalt-containing minerals are known to exist, about 30 of them are strictly cobaltiferous, but only four are widely distributed: cobaltite, CoAsS; skutterudite, CoAs₃; smaltitechloanthite, (Co,Ni,Fe)As_3–2; and safflorite, (Co,Fe)As₂. A characteristic feature of cobalt is its ability to form commercial concentrations in deposits of other metals (nickel, copper, and iron), where it occurs mainly in cobalt-containing ore minerals (pyrite, pentlandite, and asbolites), rather than only in the form of strictly cobaltiferous minerals. A distinction is made among arsenic, sulfur, and oxidized cobalt ores, according to mineral and chemical composition.

The main minerals of the arsenic cobalt ores are compounds of cobalt, nickel, and iron with arsenic (arsenides) or with arsenic and sulfur (sulfoarsenides). The arsenides include skutterudite (up to 20 percent Co), complex mixtures of smaltite-chloanthite (from 1–5 to 20 percent Co), and safflorite-loellingite (traces to 23–28 percent Co). The cobalt impurities in nickel arsenides (rammelsbergite, niccolite, and others) usually do not exceed a few percent. The following series belong to the sulfoarsenide group: cobaltite-gersdorffite and glaucodot-arsenopyrite (cobalt content ranges from negligible amounts in nickel and ferrous varieties up to 33–34 percent in strictly cobaltiferous ores). The average cobalt content in commercial ores is usually 1–2 percent. The ores may include minerals of copper, gold, silver, bismuth, and uranium. As a rule, low-grade ores are concentrated before metallurgical conversion, and high-grade ores may be used directly (in particular, by application of modern methods of hydrometallurgy); under favorable conditions, gold, silver, and other precious metals are also extracted as by-products. The arsenic cobalt ore deposits of greatest industrial importance are the Khovu-Aksy deposit (Tuva ASSR) in the USSR and the Bou Azzer region in Morocco.

Sulfurous cobalt ores belong to the group of complex nickel, copper, and iron ores. The most prominent of them are magmatic copper-nickel ores (in hyperbasic and basic rocks), as well as copper-pyrite and scarn-magnetite ores. Pentlandite is the chief cobalt-containing mineral in the first type; pyrite, with widely fluctuating content of cobalt impurities (up to 2.5–3.0 percent), is most important in the other two types. Strictly cobaltiferous sulfides—for example, cobalt-pentlandite, (Co,Fe,Ni)₉-S₈; linnaeite, Co₃S₄; carrolite, CuCO₂S₄; and cattierite, CoS₂— are relatively rare. Despite the low average cobalt content (from thousandths to hundredths and tenths of a percent), the large size of the deposits makes possible economically feasible extraction of cobalt on a large scale with complex use of the ores. Copper-nickel cobaltiferous ore deposits are located in Krasnoiarsk Krai (Noril’sk) and on the Kola Peninsula in the USSR and in the sulfide copper-nickel deposits of Canada.

Oxidized cobalt ores also belong to the complex ore group. They are formed during surface erosion of cobalt- and nickel-containing hyperbasic rocks or sulfur ores. In both the first, widely distributed type (silicate-nickel ore; about 0.1 percent cobalt), and the second, rare type (oxidized sulfur ores; 1–4 percent cobalt), the cobalt is usually concentrated in manganese hydroxides (asbolites) of variable composition, with which cobalt hydroxides and carbonates combine in the zone of oxidation. Silicate-nickel ore deposits are found in the Urals and in Kazakhstan (USSR) and in Cuba and New Caledonia; sulfur ores are found in the copper deposits of Zaire (Africa).