Introduction

Tantalum is estimated to make up between 1 and 2 ppm of the Earth’s crust by weight. There are many different Ta-containing minerals, only a few are being used as ore minerals. Tantalite (Fe,Mn)Ta2O6 is the most important mineral for tantalum production . Tantalite forms a series with columbite (Fe, Mn)(Ta, Nb)2O6; when there is more tantalum than niobium it is called tantalite and when there is more niobium than tantalum it is called columbite. Other minerals include samarskite -(Y), (Y,Ce,U,Fe)3(Nb,Ta,Ti)5O16, and fergusonite, (Ce,La,Y)NbO4. The main mining of tantalum was in Australia, in Western Australia, Greenbushes in the Southwest and Wodgina in the Pilbara region. Future resources of Ta, in order of estimated volume, are being explored in Saudi Arabia, Egypt, Greenland, China, Mozambique, Canada, Australia, the United States, Finland, and Brazil. However, it is estimated that there are less than 50 years left of Ta resources, based on present-day extraction rates, indicating the necessity for increased recycling of Ta.

Minerals

Tantalum is found in more than 50 different minerals. Within the elements class, one alloy jedwabite (Fe7(Ta,Nb)3), and one carbide tantalcarbide (TaC) are known.

About 50 minerals are found in the oxide class, which includes tantalates, for example, alumotantite (AlTaO4), bismutotantalite (Bi(Ta, Nb)O4), calciotantite (CaTa4O11), ferrowodginite (Fe²⁺Sn⁴⁺Ta2O8), fluornatromicrolite ((Na1.5Bi0.5)Ta2O6F), heftetjernite (ScTaO4), hydroxycalciopyrochlore ((Ca, Na, U)2(Nb, Ti)2O6(OH), ixiolite ((Ta, Nb, Sn, Fe, Mn)4O8), tantalite-(Mn) (Mn²⁺Ta2O6), tantite (Ta2O5), and wodginite (Mn²⁺Sn⁴⁺Ta2O8).

Be hierite ((Ta⁵⁺,Nb⁵⁺)(BO4)) and schiavinatoite ((Nb,Ta)(BO4)) are the only two borates with Ta. The same number of minerals is known in the phosphate class, johnwalkite and olmsteadite. Only two silicates have Ta in their crystal structure, holtite and zabinskiite.