XANTHOCONITE

    Class : Sulfides and sulfosalts
    Subclass : Sulfosalts
    Crystal system : Monoclinic
    Chemistry : Ag3AsS3
    Rarity : Rare

Xanthoconite is a rare sulfosalt from silver-bearing hydrothermal deposits, in which it modestly accompanies silver minerals that are much more abundant than it (pearceite, polybasite, acanthite, etc...) as well as other sulfides. Xanthoconite is the isomorph of pyrostilpnite. Its name comes from the Greek xanthos (yellow) and konis (powder) in reference to the color of its trace. Xanthoconite forms rare crystals that do not exceed 5 mm. Sometimes twinned, they are cinnamon brown in color and have a pseudohexagonal habitus. Its lamellar crystal structure is responsible for its cleavage on {001}, it has a strong adamantine luster.

Main photo : Xanthoconite from Imiter mine, Morocco © Christian Rewitzer

Xanthoconite and proustite from Imiter, Morocco © Stephan Wolfsried
Xanthoconite from Imiter, Morocco © Stephan Wolfsried
Xanthoconite from Shaft 207, Niederschlema, Germany © Uwe Haubenreisser
Xanthoconite from Ste-Marie-aux-Mines, Haut-Rhin, France © Thierry Brunsperger

Xanthoconite in the World

The best known specimens come from the Moroccan silver mines of Imiter and Freiberg (Saxony, Germany) as well as Johanngeorgenstadt, still in Saxony.

Xanthoconite in France

In France, xanthoconite is known in small crystals implanted on native arsenic at Ste-Marie-aux-Mines (Haut-Rhin).

Twinning

Twinning is known on {001} giving pseudo-orthorhombic facies.

Fakes and treatments

No fakes listed for this mineral species.


Hardness : 2 to 3
Density : 5.54
Fracture : Sub-conchoidal
Streak : Yellow-orange

TP : Translucent
RI : Greater than 3
Birefringence : -
Optical character : Biaxial -
Pleochroism : None
Fluorescence : None

Solubility : -

Magnetism : NoneRadioactivity : None