Bournonite

Bournonite is a sulfide that is metallic found in many localities worldwide but very seldom faceted. The Bournonite mineral normally called the “cog wheel ore” because of the cog wheel shape that the crystals that are twinned form. Bournonite has a bright, metallic, black colored luster and is very soft.

Bournonite is a mineral that is fairly common in a lot of localities global including Machacamarca District, Saavedra Province, Potosí Department, Bolivia; Chenzhou Prefecture, Hunan Province, China; Gard, Languedoc-Roussillon, France; Altenkirchen, Wied Iron Spar District, Westerwald, Rhineland-Palatinate, Germany; Léssolo, Canavese District, Torino Province, Piedmont, Italy; Pachapaqui District, Bolognesi Province, Ancash Department, Peru; Cerro de Pasco, Daniel Alcides Carrión Province, Pasco Department, Peru; Maramures County, Romania; Silver King Mine, Park City District, Wasatch Mountains, Summit County, Utah, United States Of America.

Chemical Formula: PbCuSbS3
Copper Lead Antimony Sulfide
Molecular Weight: 488.69 gm
Composition: Copper 13.00 % Cu
Antimony 24.91 % Sb
Lead 42.40 % Pb
Sulphur 19.68 % S
  100.00 %      

 

Crystallography: Orthorhombic – Dipyramidal
Crystal Habit: Crystals short prismatic to tabular, typically striated, as much as 11 cm across; commonly as subparallel aggregates. Also massive, granular to compact.
Twinning: Common on [110], often forms cross shapes, or if repeated, forms flat wheel shaped crystals called cog wheels.

 

Cleavage: Imperfect on {010}, less Perfect on {100} and {001}
Fracture: Irregular/Uneven, Sub-Conchoidal
Tenacity: Brittle
Moh’s Hardness: 2.5 – 3.0
Density: 5.83 (g/cm3)
Luminescence: None
Radioactivity: Not Radioactive

 

Color: Gray, Steel Gray, Black, Iron Black
Transparency: Opaque
Luster: Metallic; Brilliant to Dull
Refractive Index: n/a; Opaque
Birefringence: n/a; Opaque
Dispersion: n/a; Opaque
Pleochroism: Very Weak
Weak; color in reflected light: White