Pyrargyrite

Pyrargyrite Level 320, Cueva Santa Vein, Fresnillo, Zacatecas, Mexico Size: 3.0 x 3.0 x 2.2 cm (miniature) © danweinrich

Chemical Formula: Ag3SbS3
Locality: Fresnillo, Zacatecas, and Guanajuato, Mexico and other silver districts in the world.
Name Origin: From the Greek, pyr and argyros, “fire-silver” in allusion to color and silver content.

Pyrargyrite is a sulfosalt mineral consisting of silver sulfantimonide, Ag3SbS3. Known also as dark red silver ore or ruby silver, it is an important source of the metal.

It is closely allied to, and isomorphous with, the corresponding sulfarsenide known as proustite or light red silver ore. Ruby silver or red silver ore (German Rotgiiltigerz) was mentioned by Georg Agricola in 1546, but the two species so closely resemble one another that they were not completely distinguished until chemical analyses of both were made.

Both crystallize in the ditrigonal pyramidal (hemimorphic-hemihedral) class of the rhombohedral system, possessing the same degree of symmetry as tourmaline. Crystals are perfectly developed and are usually prismatic in habit; they are frequently attached at one end, the hemimorphic character being then evident by the fact that the oblique striations on the prism faces are directed towards one end only of the crystal. Twinning according to several laws is not uncommon. The hexagonal prisms of pyrargyrite are usually terminated by a low hexagonal pyramid or by a drusy basal plane.

History

Authors (inventeurs) : GLOCKER
Discovery date : 1831

Optical properties

Optical and misc. Properties : Translucide  –   Fragile, cassant  –   Macles possibles  –   Opaque  –
Reflective Power: 26,4-31,7% (580)
Refractive Index: from 2,88 to 3,08

Physical properties

Hardness : 2,50
Density : 5,82
Color : dark red; dark grey; black brown; violet red; red; grey black
Luster : adamantine; submetallic
Streak/Trace : dark red; red brown; purplish red
Break  : conchoidal; irregular
Cleavage: yes

Photos:

Pyrargyrite San Genaro Mine, Castrovirreyna District, Castrovirreyna Province, Huancavelica Department, Peru Size: 1.6 x 1.5 x 1.0 cm (thumbnail) © danweinrich
Pyrargyrite St Andreasberg District, Harz Mts, Lower Saxony, Germany Size: 4.0 x 3.5 x 2.0 cm (miniature) © danweinrich
Pyrargyrite Location: Fresnillo, Zacatecas, Mexico. Scale:     3 x 2.5 cm. Copyright: © Fabre Minerals
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