a natural mineral formation containing tantalum in compounds and quantities that make its industrial extraction technically feasible and economically expedient. A distinction is made between tantalum ores proper, in which Ta2O5:Nb2O5 ≥ 1, and complex tantalum-niobium ores. The main minerals of tantalum ores are columbite-tantalite, containing 30–45 percent Ta2O5; tantalite and manganotantalite, with 45–80 percent Ta2O5; wodginite, (Ta,Sn,MN)3O6, with 60–85 percent Ta2O5; and microlite, Ca2(Ta,Nb)2O6(F,OH), with 50–80 percent Ta2O5. The main minerals of tantalum-niobiumores from which both niobium and the considerably more expensive tantalum are extracted are columbite, with 5–30 percent Ta2O5; hatchettolite, (Ca,TR,U)2(Nb,Ta)2O6(F,OH)· nH2O, with 8–28 percent Ta2O5; tantalum-containing pyrochlore, with 1–1 percent Ta2O5; loparite, with 0.4–0.8 percent Ta2O5; and ixiolite, (Nb,Ta,Sn,W,Sc)3O6. The average content of Ta2O5 in tantalum ores is 0.012–0.03 percent; it occasionally ranges up to 0.24 percent, as in the deposit at Bernic Lake, Canada. Tantalum-niobium ores contain 0.02–0.05 percent Ta2O5.
Four main commercial and genetic types of tantalum ore deposits are identified.
(1) Rare-metal pegmatites of the sodium-lithium type, in which tantalum ores are usually represented by zonal vein bodies, ranging in size from a few hundred meters to 1–2 km and consisting of albite, microcline, and quartz and smaller amounts of spodumene or petalite, (LiAlSi4O10). Tantalum mineralization is characterized by Ta2O5: Nb2O5ratios between 1:1 and 3:1 and is represented by minerals of the columbite-tantalite group, such as wodginite, ixiolite, and microlite.
(2) Rare-metal tantalum-bearing granites (apogranites), which are represented by small pipes and domes of micro-cline-quartz-albite granites, often enriched with topaz and lithia micas containing fine inclusions of columbite and microlite.
(3) Crusts of weathering and deluvial-alluvial and alluvial placers, which arise in connection with the destruction of pegmatites and which contain cassiterite and minerals of the columbite-tantalite group. Crude tin is smelted from complex-ore placer concentrates, a process that produces slags containing 1–7 percent Ta205.
(4) Loparitic nepheline syenites, which have lujauvritic and foyaitic composition.
In addition, deposits of complex tantalum-niobium ore represented by carbonatites and their associated forsterite-apatite-magnetite rocks, as well as microcline-albitic riebeckitic alkaline granites and granosyenites, are coming into industrial use. A certain amount of tantalum is also extracted from the wolframites of greisen deposits.
Tantalum ores are concentrated by gravitational methods; for very fine inclusions, flotation is used. Concentrates contain from 13–15 percent (grade 3) to 26 percent (grade 2) and 40 percent (grade 1) Ta2O5; the content in concentrates obtained from niobium ores ranges from 0.4–0.6 percent to 1–1 percent Ta2O5.
The largest deposits of tantalum ores outside the USSR are found in Canada (Bernic Lake, Manitoba), Brazil (the states of Paraiba and Rio Grande do Norte), Zaïre (Shaba Province), Nigeria, Zimbabwe (Bikita), Australia (in Pilbara District and at Greenbushes), Malaysia, and Thailand (tantalum-containing tin placers). World production of tantalum in 1973 was 900 tons, of which two-thirds was produced in the USA. Reserves contained only in tantalum ores in deposits of the capitalist and developing countries are approximately 100,000 tons of Ta2O5.
REFERENCEGinzburg, A. I., and L. G. Fel’dman. “Mestorozhdeniia tantala i niobiia.” In Rudnye mestorozhdeniia SSSR, vol. 3. Moscow, 1974.
A. I. GINZBURG