Tantalum Ore

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.