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Stibiotantalite
Current inventory:  2 gems
 

Chemistry:  Sb(Ta,Nb)O₄

Discovered in 1893;   IMA status: Valid (pre-IMA; Grandfathered).
Stibiotantalite gets its name from its Antimony (Sb) content (the Greek word for Antimony is stibio) and its relation to Tantalite.

Classification

Mineral Classification:

Oxides

Strunz 8th Ed. ID:

4/D.25-30

4 : Oxides & Hydroxides
D : Oxides with metal : oxygen = 1:2 (MO2 and related compounds)
25 : Cervantite - Chiluite series

Crystal Data

Crystallography:

Orthorhombic - Pyramidal

Crystal Habit:

Crystals prismatic, flattened, may be equant, to 12 cm; striated

Twinning:

About [010] with composition plane [001]; polysynthetic

Physical Properties

Cleavage:

[001] Distinct, [100] Indistinct

Fracture:

Subconchoidal

Tenacity:

Brittle

Hardness (Mohs):

5.5

Density:

5.98 - 7.46 (g/cm³)

Luminescence:

None

Radioactivity:

Not Radioactive

Optical Properties

Color:

Yellow, Greenish Yellow, Yellowish Brown, Reddish Brown, Brown

Transparency:

Transparent to Translucent

Luster:

Adamantine to Resinous

Refractive Index:

2.374 - 2.457  Biaxial ( + )

Birefringence:

0.0826

Dispersion:

0.146; Relatively Strong; r < v

Pleochroism:

Colorless

Occurances

Geological Setting:

An uncommon accessory mineral in complex granite pegmatites.

Type Locality:

Greenbushes tin placers, Western Australia, Australia

Year Discovered:

1893

View mineral photos:

Stibiotantalite Mineral Photos and Locations

More Information

Mindat.org
Webmineral.com

Stibiotantalite is extremely rare as a faceted gem. Stibiotantalite crystals are fairly rare and usually almost opague or very heavily included, so transparent gems are extremely rare. Stibiotantalite is strongly birefringent which gives gems with any clarity a sleepy look due to doubling of the back facets when seen through the table.

Major sources of Stibiotantalite are Rio Grande do Norte, Brazil; Västerbotten, Sweden; Alto Ligonha District, Zambezia Province, Mozambique; Kola Peninsula, Russia; Mtoko, Zimbabwe; and in the USA at San Diego County, California. Most locations produce opaque to highly included crystals. Clean, facetable crystals are extremely rare.
 

  
Stibiotantalite gems for sale: