Stephanite
Stephanite is a somewhat rare silver bearing mineral. It is not a well known ore of silver but is a locally important ore in some mines. It is rarely available as a faceted gem and is for collectors of rare oddities, Black Gems or Metallic Gems. Stephanite typically forms as nicely shaped crystals that are tabular to short prismatic.
Stephanite is available from many silver mining localities, typically in small amounts, and only rarely in fine specimens. In Germany, at the Type Locality of Freiberg, Schneeberg, and Marienberg, Saxony; and as exceptional crystals from St. Andreasberg, Harz Mountains. In Slovakia, at Banská Hodrusa and from Banská Stiavnica (Schemnitz). In the Czech Republic, at Jáchymov (Joachimsthal), Príbram, and Trebsko. In Italy, fine twins from Monte Narba, near Sarrabus, Sardinia. In England, as twinned crystals from Wheal Boys, St. Endellion, Cornwall. At Espedalen, Norway. From Azegour, Morocco. At Altyn-Topkan, Tadjikistan. In Canada, in the Cobalt district, Ontario; at United Keno Hill Mines, and fine examples from the Husky mine, Elsa, Yukon Territory. In the USA, in Nevada, as an important ore mineral in the Comstock Lode, Virginia City, Storey County In Mexico, large crystals from Arizpe, Sonora; at Guanajuato; from Fresnillo, Zacatecas. At Chañarcillo, south of Copiapó, Atacama, Chile. In Bolivia, from Colquechaca, Potosí. At San Cristobal, Peru. From Broken Hill, New South Wales, Australia.
| Chemical Formula: | Ag5SbS4 |
| Silver Antimony Sulfide | |
| Molecular Weight: | 789.36 gm |
| Composition: | Silver | 68.33 % | Ag | ||
| Antimony | 15.42 % | Sb | |||
| Sulfur | 16.25 % | S | |||
| Oxygen | 45.99 % | O | |||
| 100.00 % |
| Crystallography: | Orthorhombic – Pyramidal |
| Crystal Habit: | Crystals short prismatic to tabular [001], to 6 cm, also elongated along [100], with {110} striated parallel to [114]; massive, compact and disseminated. |
| Twinning: | On {110}, commonly repeated to form pseudohexagonal groups; less common on {130}, {100} and {010}, with composition plane {001}. |
| Cleavage: | Imperfect on {010} and {021} |
| Fracture: | Sub-Conchoidal |
| Tenacity: | Brittle |
| Moh’s Hardness: | 2.0 – 2.5 |
| Density: | 6.26 (g/cm3) |
| Luminescence: | None |
| Radioactivity: | Not Radioactive |
| Color: | Iron-Black; in polished section, pale Gray |
| Transparency: | Opaque |
| Luster: | Metallic |
| Refractive Index: | R1–R2: (400) 32.0–33.0, (420) 32.1–33.2, (440) 32.2–33.4, (460) 31.5–33.2, (480) 30.7–32.6, (500) 30.0–32.0, (520) 29.0–31.3, (540) 28.4–30.6, (560) 28.0–30.2, (580) 27.6–29.8, (600) 27.5–29.6, (620) 27.6–29.6, (640) 27.8–29.5, (660) 28.0–29.2, (680) 28.5–28.7, (700) 28.2–28.2 |
| Birefringence: | 0.00 |
| Dispersion: | n/a |
| Pleochroism: | Very Weak; white to pale pink |
| Anisotrophism: | Strong; in vivid colors |
