NAUMANNITE

    Class : Sulfides and sulfosalts
    Subclass : Selenides
    Crystal system : Monoclinic
    Chemistry : Ag2Se
    Rarity : Rare

Naumannite is the principal silver selenide. It is a rare mineral from selenide silver hydrothermal veins, the selenium equivalent of acanthite and argentite, with which it is commonly associated, at the same time as other selenides (particularly clausthalite). It was named in honor of the German mineralogist and crystallographer Carl Friedrich Naumann. Naumannite is mainly massive, rarely in pseudocubic crystals, of a black color with a metallic luster, tarnishing to brownish with iridescence.

Main photo : Naumannite from Zalesi, Javornic, Czech Republic © Pavel Skacha

Naumannite in the World

Naumannite is present in the polymetallic selenide veins of the German Harz (St-Andréasberg, Tilkerode) where it was discovered more than a century ago, and in beautiful samples at Kongens near Kongsberg (Norway). It is also known in the epithermal gold veins of Sacarimb in Romania and in the uranium veins of Pribram (Czech Republic). Naumannite is also reported in several American localities in Idaho and Washington, and in the "abnormally" selenide-rich veins of Cacheuta (Argentina) and Pacajake (Bolivia).

Right photo : Naumannite from De Lamar Mine, Idaho, USA © Marco Burkhardt

Naumannite in France

In France, naumannite is reported at Quistiav (Morbihan).

Twinning

No twins known for this mineral species.

Fakes and treatments

No fakes recorded for this mineral species.


Hardness : 2.5
Density : 7 to 8
Fracture : Hackly
Streak : Black

TP : Opaque
RI : -
Birefringence : -
Optical character : -
Pleochroism : None
Fluorescence : None

Solubility : -

Magnetism : NoneRadioactivity : None

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