Tantalum and niobium raw materials

Niobium and tantalum are rare elements. The content of niobium and of tantalum in the Earth s crust is 1 x 10 3 and 2x 1 O 4 wt. %, respectively [21]. Niobium and tantalum are encountered in nature together, mostly in the form of oxides that are derived from orthoniobic (orthotantalic), metaniobic (metatantalic) and pyroniobic (pyrotantalic) acids. The main minerals are listed in Table 2, which reveals that the most important source of tantalum and niobium is tantalite-columbite, (Fe,Mn)(Nb,Ta)206. 

Deposits of niobium-tantalum ores are found in Australia, Brazil, Canada, China, Malaysia, Namibia, Nigeria, Russia, Rwanda, Spain, Thailand, Zaire, and Zimbabwe. A more detailed analysis of worldwide tantalum mineral raw material supply can be found in Linden s comprehensive overview [22, 23], 

The niobium-tantalum weight ratio in North American pyrochlores is 100-150 1, while in Russian ores the ratio varies between 8 1 and 1 20 [21]. 

Additional sources of the elements are tin slag and scrap. For instance, cassiterite deposits, in Australia, Brazil, Thailand and some other countries, contain a significant amount of tantalum. The bulk of this tantalum is collected in the slag and processed separately. Recycling of various tantalum-bearing scrap is also a very important source for tantalum production. These scrap materials include powder surplus from sintering operations, scrap from mill products, rejected and used capacitors, scrapped cutting tools and furnace hardware. 

---