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 |
