Vanadinite

General

 

Category: Vanadate mineral Apatite group

 

Formula: Pb5(VO4)3Cl

 

Strunz classification: 08.BN.05

 

Crystal symmetry: Hexagonal 6/m – dipyramidal

 

Unit cell: a = 10.3174 Å, c = 7.3378 Å, Z=2

 

 

Identification

 

 

Formula mass: 1416.27 g/mol

 

Colour: Bright red, orange-red, red-brown, brown, yellow, grey or colourless, may be concentrically zoned

 

Crystal habit: Prismatic or nodular; may be acicular, hairlike, fibrous; rarely rounded, globular

 

Crystal system: Hexagonal dipyramidal 6/m

 

Cleavage: None

 

Fracture: Uneven to conchoidal

 

Tenacity: Brittle

 

Mohs scale hardness: 3–4

 

Luster: Resinous to sub-adamantine

 

Streak: brownish yellow

 

Diaphaneity: Transparent, translucent or opaque

 

Specific gravity: 6.8–7.1 (measured) 6.95 (calculated)

 

Optical properties: Uniaxial (-)

 

Refractive index: nω = 2.416, nε = 2.350

 

Birefringence: δ = 0.066

 

Ultraviolet fluorescence: None

 

Done