DUFRENOYSITE

    Class : Sulfides and sulfosalts
    Subclass : Sulfosalts
    Crystal system : Monoclinic
    Chemistry : Pb2As2S5
    Rarity : Very rare

Dufrenoysite is a very rare lead sulfoarsenide, present in hydrothermal gold deposits (Hemlo, Canada), and in hydrothermalized dolomites (Binn, Switzerland). It was named in honor of Pierre Armand Dufrénoy, professor of Mineralogy at the Ecole des Mines de Paris. It forms tabular crystals with a maximum size of 2.5 cm, moderately elongated along [100] or [010], striated along [100], lead gray to steel gray in color. It accompanies various arsenic and antimony minerals (realgar, orpiment, tetrahedrite) and, in Binn, other extremely rare lead sulfoarsenides (rathite, baumhauerite, sartorite, etc...).

Main photo : Dufrenoysite and realgar from Lengenbach Quarry, Fäld, Binn, Goms, Valais, Switzerland © Joy Desor

Dufrenoysite from Lengenbach Quarry, Valais, Switzerland © Stephan Wolfsried
Dufrenoysite from Lengenbach Quarry, Valais, Switzerland © Edgar Müller
Dufrenoysite from Lengenbach Quarry, Valais, Switzerland © Enrico Bonacina
Dufrenoysite from Lengenbach Quarry, Valais, Switzerland© Stephan Wolfsried

Dufrenoysite in the World

The only crystals of museological interest come from the Swiss deposit of Lengenbach, near Binn (Switzerland). Apart from this, dufrenoysite is reported in numerous American localities (Utah, California, Arizona, Nevada, etc...), in English Cornwall, in Australia, Austria, Italy, China, etc...

Dufrenoysite in France

Dufrenoysite is not present in the French subsoil.

Twinning

A twin is known on {001}.

Fakes and treatments

No fake listed for this mineral species.


Hardness : 3
Density : 5.50 to 5.57
Fracture : Conchoidal
Streak : Brown

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

Solubility : -


Magnetism : None
Radioactivity : None