Argyrodite

Argyrodite, silver germanium sulfide Ag8GeS6 is relatively scarce mineral. The colour is iron-black with a purplish tinge, and the lustre metallic. Discovered by Clemens Winkler in 1886 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 occurs in the Himmelsfurst Mine, Freiberg, Saxony and in Bolivia.It is of interest to note that the Freiberg mineral was long ago imperfectly described by August Breithaupt under the name Plusinglanz, and that the Bolivian crystals were incorrectly described in 1849 as crystallized brongniardite.
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Noun
1. a rare steel-gray mineral consisting of silver and germanium and sulfur
(hypernym) mineral
(substance-meronym) germanium, Ge, atomic number 32

General Information:
 Chemical Formula:
Ag8GeS6
 Composition:
(Molecular Weight = 1,127.95 gm)
Silver 76.51 % Ag
Germanium 6.44 % Ge
Sulfur 17.06 % S 
 Empirical Formula:
Ag8GeS6
 Locality:
Himmelsfurst mine, Freiberg, Saxony.
Physical Properties:
 Cleavage:
None
 Color:
black or steel gray.
 Density:
6.1 - 6.3, Average = 6.19
 Diaphaniety:
Opaque
 Habits:
Subhedral Crystals - Occurs as crystals which tend to exhibit a recognizable crystal shape., Massive - Granular - Common texture observed in granite and other igneous rock.,
 Hardness:
2.5 - Finger Nail
 Luster:
Metallic
 Streak:
grayish black
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ARGIRODITE