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 | |
|---|---|
Tantalite, Pilbara district, Australia | |
| General | |
| Category | Oxide minerals |
| Formula (repeating unit) | (Fe,Mn)Ta2O6 |
| IMA symbol | Ttl |
| Strunz classification | 4.DB.35 |
| Crystal system | Orthorhombic |
| Crystal class | Dipyramidal (mmm) H-M symbol: (2/m 2/m 2/m) |
| Space group | Pbcn (no. 60) |
| Identification | |
| Color | Dark black, iron-black to dark brown, reddish brown |
| Cleavage | Good in one direction |
| Fracture | Subconchoidal |
| Mohs scale hardness | 6–6.5 |
| Luster | Submetallic to almost resinous |
| Streak | Brownish-red to black |
| Specific gravity | 8.0+ |
| References | |
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.