natural mineral formations containing tungsten in amounts that make their extraction economically feasible. The chief minerals of tungsten are wolframite, containing 74-76 percent WO3, and scheelite, containing 80 per-cent WO3. The minimum concentrations of tungsten trioxide at which it is profitable to work tungsten ores at the present level of economic and technological development (1960-70) are of the order of 0.14—0.15 percent for large deposits and 0.4-0.5 percent for smaller, vein deposits. Tungsten ores often contain other useful components (tin, molybdenum, beryllium, gold, copper, lead, and zinc). In addition, the wolframites of some deposits contain large amounts of tantalum and scandium, which can be extracted from them. To obtain concentrates containing 50-60 percent WO3, the ores are enriched using gravitational, flotation, and other methods of concentration.
Endogenic deposits of tungsten are postmagmatic, pneumatolytic, or hydrothermal and are genetically associated with granite intrusions. The following types of tungsten ore deposits are differentiated: albitized, greisened, and silicified cupolas and stocks of granites or granitized porphyry, containing finely disseminated wolframite and some-times thin quartz-wolframite veins and forming a stockwork; quartz-feldspar, quartz-topaz, quartz-fluorite, and quartz veins, often with greisen selvages containing wolframite and rarely scheelite, cassiterite, beryl, arsenopyrite, bismuthinite, molybdenite, pyrite, and other sulfides; quartz-scheelite veins, mineralized zones, and stock works, often containing sulfides; quartz-gold-scheelite and quartz-antimonitescheelite bodies containing ferberite, antimonite, cinnabar, and barite; and scheelite-containing scarns of garnetpyroxene-scapolite composition, containing molybdenite, chalcopyrite, galena, and sphalerite. The richest are deposits of the vein type, which often contain up to several percent WO3. The largest deposits are the skarn and stockwork types. Deluvial and alluvial placers containing wolframite and scheelite may form because of erosion of direct deposits.
There are large deposits of tungsten ores in the USSR (Transbaikalia, Middle Asia, Kazakhstan, Primor’e, and the Northeast), the People’s Republic of China, and the Korean Democratic People’s Republic. Capitalist countries prominent for their reserves and mining of tungsten ores (1966 output in tons of WO3) include the USA (4,852), Bolivia (1,580), Australia (1,326), Portugal (1,199), Peru (437), Thai-land (336), and Burma (207).
REFERENCESBybochkin, A. M. Mestorozhdeniia vol’frama i zakonomernosti ikh razmeshcheniia. Moscow, 1965.
Mineralogiia i geokhimiia vol’framovykh mestorozhdenii. [Leningrad] 1967.
A. I. GINZBURG