THE MINERAL STEPHANITE

  • Chemistry: Ag5SbS4, Silver Antimony Sulfide
  • Class: Sulfides
  • Subclass: Sulfosalts
  • Uses: An ore of silver and as mineral specimens.
  • Specimens

Stephanite is an uncommon silver bearing mineral that is named after a onetime Archduke of Austria, Victor Stephan. Although not a well known ore of silver, it is never-the-less a locally important ore in some mines. Stephanite typically forms nicely shaped crystals that are tabular to short prismatic. Its crystals can have a pseudohexagonal outline making them look like crystals of polybasite, a closely related mineral. Stephanite lacks polybasite's rhombic striations on its pinacoidal faces, good cleavage and the red flashes.

PHYSICAL CHARACTERISTICS:

  • Color is an iron black to dark gray.
  • Luster is metallic.
  • Transparency: Crystals are opaque.
  • Crystal System: Orthorhombic; 2 m m
  • Crystal Habits include tabular or short prismatic crystals that are dominated by prominent pinacoidal faces. Crystals are sometimes intergrown and form pseudohexagonal plates. Also as disseminated grains and massive.
  • Cleavage is poor in two directions.
  • Fracture is conchoidal to uneven.
  • Hardness is 2 - 2.5
  • Specific Gravity is approximately 6.2 - 6.3 (heavy even for metallic minerals)
  • Streak is a black.
  • Other Characteristics: Dark coating can often form after prolonged exposure to light (can be removed by ultrasonic treatment) and crystals tend to be striated perpendicular to the prominent pinacoids.
  • Associated Minerals include silver, proustite, pyrargyrite, polybasite, sphalerite, quartz, barite, calcite, pyrite, fluorite, galena, tetrahedrite , acanthite and other silver sulfide minerals.
  • Notable Occurrences include Sonora, Mexico; Freiberg, Saxony, Germany; Colorado, California and Comstock, Nevada, USA; Atacama, Chile; Cobalt, Ontario, Canada; Cornwall, England and Bolivia.
  • Best Field Indicators are good crystal habit, density, softness, association with other silver sulfosalts and lack of cleavage.
This Site Awarded
Available STEPHANITE specimens:
see this List of ALL specimens including SOLD ones

 

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