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