Wolframite

WOLFRAMITE (EN: wolframite; DE: Wolframit; FR: wolframite; ES: wolframita; RU: вольфрамит) is the mineral of the class of the tungstates, (Mn,Fe)WO4. The content of the WO3 is 74-76%. Sometimes, there exist the admixtures of Ca, Nb, Ta, Mg (mostly in the form of the micro-inclusions of the scheelite, columbite, and other minerals). The wolframite represents by itself the series of the solid solutions with the variable composition, with the hübnerite MnWO4 and ferberite FeWO4 as the end members.

The wolframite crystallizes into the monoclinic crystal system. At the basis of the crystal structure, there are the zigzag-shaped chains of the (Mn,Fe)O6 and WO6 octahedra. The wolframite forms the crystals (often zoned) of various shapes; short prismatic, long prismatic, short columnar, long columnar, acicular, and so on; there is characteristic the vertical striation on the facets. Often there are observed the twin crystals. There are most usual the aggregates of the elongated-lamellar or acicular grains, radiant intergrowths, continuous granular masses. There are known the pseudomorphs of the wolframite on the scheelite (and conversely). The colour of the wolframite is brown-black (the ferberite is black, the hübnerite is red-brown). The lustre is metallic, semimetallic, greasy, resinous, and adamantine. Sometimes, there is noted the rainbow iridescence. The wolframite is brittle. The cleavage is perfect along one direction. The hardness is 5-5.5. The density is from 7100-7200 (hübnerite) to 7500-7600 (ferberite) kilograms per cubic metre.

The wolframite is the hydrothermal mineral of the quartz veins and greisens, it often associates with the cassiterite or molybdenite (the deposits of tungsten within the Jiangxi province of the People's Republic of China; the Mochi and Haminji within Burma; within the USSR, the Spokoyninskoe, Bom Gorhonskoe, Dzhidinskoe, and other deposits within the Transbaikalia, the Akchatauskoe, Karaobinskoe, and other deposits within the Central Kazakhstan). The wolframite is also typical for the hydrothermal tin-lead-zinc deposits (Potosí and others within Bolivia; Akenobe and others within Japan). The ferberite may be encountered within the low-temperature antimony-tungsten deposits, in association with the stibnite (Barun-Shiveya within the eastern Transbaikalia; Zophito within the Georgia country). The wolframite is quite resistant against the weathering, there are known its placer deposits. The wolframite, along with the scheelite, is the main mineral of the tungsten ores.

The wolframite is beneficiated using the gravitational and magnetic methods. The wolframite is extracted from the sludges mostly using the flotation. The collectors are: oleic acid (pH is 7 and 10), alkyl sulfates (pH is 4-9.5), cupferron, petroleum oils, unsaturated fatty acids; the regulators of the medium are: alkali, soda, sulfuric acid or hydrochloric acid; the activators are: salts of divalent manganese; the depressors are: liquid glass, iron sulfate. For the separation of the large-grained material, there is used the flotation-gravitation. During the refinement of the concentrates, there are used the electromagnetic separation, electrostatic separation, and roasting.

During the hydrometallurgical processing of the concentrates of the wolframite from the greisen and quartz-veinous tin-tungsten deposits, there are obtained the cakes, from which there is possible the extraction of tantalum.