Tantalite is the primary ore source of tantalum. It has the unit formula (Fe,Mn)Ta2O6 and forms a series with columbite. The crystal system is orthorhombic and the colour ranges from black through brown to red/brown. Its hardness is 6-6.5 on the Mohs scale and the specific gravity is around 8. Microlite is a tantalum containing mineral, forming a series with pyrochlore. The general formula for Microlite is (Na,Ca)2Ta2O6(O,OH,F). it has a black, through red/brown to yellow colour, has a Mohs hardness of 5.5, and a specific gravity of 4.2-6.4.
The value of Tantalite is determined by the content of Ta2O5, measured in pounds (lb), with a price paid in US dollars per pound of Ta2O5 contained. No additional value is paid for any niobium pentoxide contained. There is no trading on tantalum on exchange, and price is determined by negotiation between buyer and seller.
Our traded tantalite is physically processed and typically contains > 30% tantalum pentoxide, with a mean niobium pentoxide content of 25%, Sb < 20 ppm, and WO3 < 0.5% by mass.