Wulfenite

General

 

Category: Molybdate mineral

 

Formula (repeating unit): PbMoO4

 

Strunz classification: 7.GA.05

 

Crystal system: Tetragonal

 

Crystal class: Dipyramidal (4/m) H-M symbol: (4/m)

 

Space group: I41/a

 

Unit cell: a = 5.433, c = 12.110 [Å]; Z = 4

 

 

Identification

 

Color: yellow, honey-yellow, Orange-yellow, reddish-orange, rarely colorless, grey, brown, olive-green and black.

 

Crystal habit: Thin tabular to pyramidal

 

Twinning: Twins on the [001] common

 

Cleavage: On {011}, distinct; on {001}, {013}, indistinct

 

Fracture: Irregular to sub-conchoidal

 

Tenacity: Brittle

 

Mohs scale hardness: 3

 

Luster: Adamantine, resinous

 

Streak: White

 

Diaphaneity: Transparent to opaque

 

Specific gravity: 6.5-7.0

 

Optical properties: Uniaxial (-), may be anomalously biaxial

 

Refractive index: nω = 2.405 nε = 2.283

 

Birefringence: δ = 0.122

 

Pleochroism: Weak; orange and yellow

 

Ultraviolet fluorescence: None

 

Other characteristics: Specimens may be piezoelectric

 

Done