Argyrodite

Argyrodite

Argyrodite from the type location in Germany (size: 4.9 x 3.2 x 2.3 cm)
General
Category Sulfide mineral
Formula
(repeating unit)		 Ag8GeS6
Strunz classification 02.BA.35
Crystal symmetry Orthorhombic mm2 pyramidal
Unit cell a = 15.149 Å, b = 7.476 Å, c = 10.589 Å; Z = 4
Identification
Color Black, purplish tinge
Crystal habit Pseudo-octahedra, dodecahedra, cubes; radiating crystal aggregates, botryoidal crusts, or massive
Crystal system Orthorhombic - pseudo-cubic
Twinning Pseudospinel law {111} penetration twins
Cleavage Absent
Fracture Uneven to conchoidal
Mohs scale hardness 2.5
Luster Metallic
Diaphaneity Opaque
Specific gravity 6.2-6.5
Optical properties Weakly anisotropic
Pleochroism Weak
References [1][2]

Argyrodite is an uncommon silver germanium sulfide mineral with formula Ag8GeS6. The color is iron-black with a purplish tinge, and the lustre metallic.

Discovered by Clemens Winkler in 1886,[3] it is of interest as it was described shortly after the element germanium was isolated, 15 years after it had been postulated by Mendeleev. It was first described for an occurrence in the Himmelsfürst Mine, Erzgebirge, Freiberg, Saxony, Germany.[2]

The Freiberg mineral had previously been imperfectly described by August Breithaupt under the name plusinglanz, and Bolivian crystals were incorrectly described in 1849 as crystallized brongniardite.[3]

Isomorphous with argyrodite is the corresponding tin bearing mineral Ag8SnS6, also found in Bolivia as pseudocubic crystals, and known by the name canfieldite.[3] There is also a related mineral, putzite, with composition (Cu4.7Ag3.3)GeS6.

Argyrodite gets its name from the Greek words that loosely translate into "rich in silver".[1]

References

  1. ↑ 1.0 1.1 Handbook of Mineralogy
  2. ↑ 2.0 2.1 Mindat.org
  3. ↑ 3.0 3.1 3.2 Spencer 1911, p. 488.
Attribution