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The Mineral tantalite

Blocky Black Tantalite

Tantalite forms a solid solution series with Columbite known as the Columbite-Tantalite series. Tantalite is the tantalum-rich member, and Columbite is the niobium-rich member. Tantalite is named after its tantalum content, and, together with Columbite, are the most important minerals containing the rare element tantalum.

The name Tantalite has been discredited by the IMA, with the more specific designations of Tantalite-(Fe) (also known as Ferrotantalite), and Tantalite-(Mn) (also known as Manganotantalite) being used for this mineral's IMA-accepted nomenclature. Ferrotantalite is always dark and opaque; Manganotantalite is usually reddish-brown and may exhibit transparency. An even rarer member of this series is Tantalite-(Mg) (Magnesiotantalite), a magnesium-rich member. In general, despite being discredited, the name Tantalite is still used without further designation, and often it is simply labelled as Columbite-Tantalite, since the exact species can be difficult to determine.

Chemical Formula

Ferrotantalite: (Fe,Mn)(Ta,Nb)₂O₆

Manganotantalite: (Mn,Fe)(Ta,Nb)₂O₆

Magnesiotantalite: (Mg,Mn,Fe)(Ta,Nb)₂O₆

Color

Dark reddish-black, dark red, dark gray, reddish-brown

Crystal System

Orthorhombic

Properties

Streak
Dark red, dark brown, black

Hardness
6 - 6.5

Transparency
Ferrotantalite is opaque. Manganotantalite is usually translucent, and rarely transparent.

Specific Gravity
6.5 - 8.3

Luster
Submetallic, greasy, dull

Cleavage
1,1

Fracture
Conchoidal, uneven

Tenacity
Brittle

Crystal Habits

In prismatic and tabular crystals, often with a somewhat flattened or blocky appearance. Crystals may be striated or have growth patterns, and sometimes have complex terminations including uneven tapering habits and pyramidal. Crystals are often crudely formed, and may have undefined faces. Also bladed, grainy, and massive.

3D Crystal Atlas

Additional Information

Composition
Oxide of iron, manganese, tantalum, and niobium. One series member contains a dominance of magnesium.

In Group
Oxides; Multiple Oxides

Striking Features
Crystal habit, mode of occurrence, and high specific gravity.

Environment
In granite pegmatites, as well as alluvial deposits containing weathered pegmatite fragments.

Rock Type
Igneous

Uses

Tantalite is as an ore of the rare elements tantalum and niobium.

Noteworthy Localities

Localities for Tantalite are pretty much the same as Columbite, and it often is not identified individually but more generally as Columbite-Tantalite. Specific localities that have produced exceptional Tantalite include the São Pedro Mine, Malacacheta, Minas Gerais, Brazil, where it was found in blocky crystals; the Shigar Valley, Skardu, Gilgit-Baltistan, Pakistan, as pseudomorphs of Microlite; and Ankole, Mbarara District, Uganda; where the manganese-rich end member has been found in dark red, translucent crystals.