Galena

General

 

Category: Sulfide mineral, octahedral subgroup

 

Formula

(repeating unit): PbS

 

Formula (repeating unit): PbS

 

Strunz classification: 2.CD.10

 

Dana classification: 2.8.1.1

 

Crystal system: Cubic

 

Space group: Fm3m

 

Unit cell: a = 5.936 Å; Z = 4

 

 

Identification

 

Color: Lead gray and silvery

 

Crystal habit: Cubes and octahedra, blocky, tabular and sometimes skeletal crystals

 

Twinning: Contact, penetration and lamellar

 

Cleavage: Cubic perfect on [001], parting on

 

Fracture: Subconchoidal

 

Tenacity: Brittle

 

Mohs scale hardness: 2.5–2.75

 

Luster: Metallic on cleavage planes

 

Streak: Lead gray

 

Diaphaneity: Opaque

 

Specific gravity: 7.2–7.6

 

Optical properties: Isotropic and opaque

 

Fusibility: 2

 

Other characteristics: Natural semiconductor

Done