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Tantalite-(Fe)  (formerly Ferrotantalite)
Current inventory:  0 gems
 

  
Tantalite-(Fe), formerly known as Ferrotantalite, is named for its dominant ferrous iron (Fe) content and the Greek mythological Tantalus (father of Niobe) for the difficulty of dissolving the mineral.

Discovered in 1836;   IMA status: Valid (pre-IMA; Grandfathered; renamed in 2008)

Chemistry

Chemical Formula:

FeTa₂O₆

Iron Tantalum Oxide

Molecular Weight:

513.74 gm

Composition: 

Classification

Mineral Classification:

Oxides

Strunz 8th Ed. ID:

4/D.18-50

Nickel-Strunz 10th Ed. ID:

4.DB.35

4 : OXIDES (Hydroxides, V[5,6] vanadates, arsenites, antimonites, bismuthites, sulfites, selenites, tellurites, iodates)
D : Metal: Oxygen = 1:2 and similar
B : With medium-sized cations; chains of edge-sharing octahedra

Related to:

Tantalite-(Fe)-Tantalite-(Mn) Series. Tantalite-(Fe)-Columbite-(Fe) Series. Dimorphous with Ferrotapiolite.

Synonyms:

Coltan, Columbite-Tantalite, Ferrotantalite, Siderotantalite

Crystal Data

Crystallography:

Orthorhombic - Dipyramidal

Crystal Habit:

Commonly as exsolution intergrowths with ferrotapiolite.

Twinning:

None

Physical Properties

Cleavage:

{100} Distinct, {010} less Distinct

Fracture:

Irregular/Uneven, Sub-Conchoidal

Tenacity:

Brittle

Moh's Hardness:

6.0 - 6.5

Density:

6.65 - 7.95 (g/cm³)

Luminescence:

None

Radioactivity:

Not Radioactive

Other:

Paramagnetic

Optical Properties

Color:

Iron-Black; Reddish Brown in transmitted light; Gray in reflected light with Red to Reddish Brown internal reflections

Transparency:

Opaque, translucent on thin edges

Luster:

Vitreous, Submetallic

Refractive Index:

2.260 - 2.430  Biaxial ( - )

Birefringence:

0.170

Dispersion:

Relatively Strong; r < v

Occurances

Geological Setting:

As an accessory and primary constituent of granite pegmatites.

Common Associations:

Ferrotapiolite

Type Locality:

Upper Bear Gulch, Tinton pegmatite District, Lawrence Co., South Dakota, USA

Year Discovered:

1836; IMA changed name from Ferrotantalite to Tantalite-(Fe) in 2008

View mineral photos:

Tantalite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Tantalite-(Fe) is a fairly rare mineral that is rarely available as a faceted gem. It is closely related to Tantalite-(Mn), Columbite-(Fe) and Tapiolite-(Fe). Tantalite and Columbite are often grouped together as a semi-singular mineral called Columbite-Tantalite or Coltan. However, Tantalite has a much greater specific gravity than Columbite (up to 8.0 for Tantalite compared to Columbite's 5.2). Iron- rich Tantalite is the mineral Tantalite-(Fe), formerly known as Ferrotantalite, and manganese-rich Tantalite is Tantalite-(Mn), formerly known as Manganotantalite.

Tantalite is also very closely related to Tapiolite. The two minerals have the same chemical composition, but different crystal structures; Orthorhombic for Tantalite and Tetragonal for Tapiolite.

Tantalite is found as brown to black opaque crystals and Manganotantalite can be found as brown to red translucent to transparent crystals and is rarely available as faceted gems that can be very attractive. Some Tantalite specimens may show a bluish iridescence and have weak magnetism.

Material analyzed by microprobe from: Moss, Norway. At Spittal an der Drau, Austria. In the Yellowknife district, Northwest Territories, Canada. At Muhembe, Rwanda. From Nyanga, Uganda. At Upper Bear Gulch, Lawrence County, South Dakota, USA.
 

  
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