Tantite

Tantite is a rare tantalum oxide mineral with formula: Ta₂O₅. Tantite forms transparent microscopic colorless triclinic - pedial crystals with an adamantine luster. It has a Mohs hardness of 7 and a high specific gravity of 8.45. Chemical analyses show minor inclusion (1.3%) of niobium oxide.

Tantite
General
Category	Oxide minerals
Formula	Ta2O5
IMA symbol	Tan[1]
Strunz classification	4.EA.05
Dana classification	04.06.06.01
Crystal system	Triclinic
Crystal class	Pedial (1) (same H-M symbol)
Space group	P1
Unit cell	a = 3.8 Å, b = 3.79 Å c = 35.74 Å; β = 90.18°; Z = 6
Identification
Formula mass	441.89 g/mol
Color	Colorless
Cleavage	None
Mohs scale hardness	7
Luster	Adamantine
Streak	White
Diaphaneity	Transparent
Specific gravity	8.55
Density	8.45 g/cm3
Optical properties	Biaxial
References	[2][3]

It was first described in 1983 for an occurrence in a pegmatite in the Kola peninsula, Russia. It has also been reported from a pegmatite complex in Florence County, Wisconsin. Associated mineral species include elbaite, lepidolite, spodumene, columbite-tantalite, wodginite, and microlite.