Tantalite

The mineral group tantalite [(Fe, Mn)Ta2O6] is the primary source of the chemical element tantalum, a corrosion (heat and acid) resistant metal. It is chemically similar to columbite, and the two are often grouped together as a semi-singular mineral called coltan or "columbite-tantalite" in many mineral guides. However, tantalite has a much greater specific gravity than columbite (8.0+ compared to columbite's 5.2). Iron-rich tantalite is the mineral tantalite-(Fe) or ferrotantalite and manganese-rich is tantalite-(Mn) or manganotantalite. Tantalite is also very close to tapiolite. Those minerals have the same chemical composition, but different crystal symmetry: orthorhombic for tantalite and tetragonal for tapiolite. Tantalite is black to brown in both color and streak. Manganese-rich tantalites can be brown and translucent.