Freibergite: Properties and Occurrences

Freibergite is a complex sulfosalt mineral of silver, copper, iron, antimony and arsenic with formula (Ag, Cu, Fe)12(Sb, As)4S13. It is a complex cubic sulfosalt mineral of silver, copper, iron, antimony, and arsenic. It has cubic crystals and is formed in hydrothermal deposits. It forms one solid solution series with tetrahedrite and another with argentotennantite.

The mineral was first described in 1853 from an occurrence in the silver mines of the type locality at Freiberg, Saxony.

General Information

  • Category: Sulfosalt minerals
  • Formula: (Ag,Cu,Fe)12(Sb,As)4S13
  • Crystal system: Cubic
  • Crystal class: Hextetrahedral (43m)

Fig: Freibergite

Properties

Freibergite is an opaque, metallic steel grey to black and leaves a reddish-black streak. It has a Mohs hardness of 3.5 to 4.0 and a specific gravity of 4.85 – 5. It is typically massive to granular inhabit with no cleavage and an irregular fracture.

  • Formula mass: 1,929.46 g/mol
  • Color: Steel gray to black
  • Crystal habit: massive to well-formed crystals
  • Fracture: Uneven
  • Mohs scale hardness: 3.5 – 4
  • Luster: Metallic
  • Streak: reddish black
  • Diaphaneity: Opaque

Occurrence: In hydrothermal deposits.

Association: A wide variety of sulfides and sulfosalts, as for tetrahedrite.

 

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