Tantalite Value, Price, and Jewelry Information

Rob Lavinsky, iRocks.com – CC-BY-SA-3.0 [CC-BY-SA-3.0], via Wikimedia Commons

Tantalite

Tantalite is too dark to be of use as a faceted gem but is sometimes cut as a collector curiosity, either faceted or in cabochons. These could be of any desired size.

Tantalite Information

Data Value
Name Tantalite
Varieties Manganotantalite
Colors Black, brownish black, reddish brown; may tarnish iridescent.
Crystallography Orthorhombic. Crystals tabular prismatic, in aggregates, massive, compact.
Refractive Index 2.26-2.43
Luster Submetallic to vitreous.
Hardness 6-6.5
Fracture Uneven
Specific Gravity 8.2; decreases with Ta content (columbite, 5.2).
Birefringence 0.160
Cleavage Distinct 1 direction
Stone Sizes Very large crystals weighing many pounds have been found. The material is usually dark colored, opaque, and of interest only for cabochons.
Luminescence None.
Luminescence Present No
Transparency Transparent.
Absorption Spectrum Not diagnostic.
Formula

(Fe,Mn)(Nb,Ta)2O6.

Pleochroism

Strong; brown/red-brown.

Optics

a = 2.26; β = 2.30-2.40; γ = 2.43. Biaxial (+), 2V Large. Usually opaque, indices measured on powders or thin splinters

Optic Sign Biaxial +

TANTALITE Series to Columbite: (Fe,Mn)(Nb,Ta)2O6.

Streak: Black, brownish black, reddish brown.

Optics: a= 2.26; β= 2.30-2.40; γ=2.43.

Biaxial (+), 2VLarge. Usually opaque, indices measured on powders or thin splinters

Spectral: Not diagnostic.

Occurrence: In granite pegmatites.

Colorado; Wyoming; New England.

Canada; Brazil; Madagascar; France; Sweden: Finland; USSR; Zimbabwe; Western Australia.

South Dakota: various localities.

California: various localities.

Comments: Tantalite is too dark to be of use as a faceted gem but is sometimes cut as a collector curiosity, either faceted or in cabochons. These could be of any desired size.

Name: After the mythical character Tantalus, because it is difficult to dissolve the mineral in acids prior to analysis.