MIXITE

    Class : Phosphates, arsenates, vanadates
    Subclass : Hydrated arsenates
    Crystal system : Hexagonal
    Chemistry : Cu6Bi(AsO4)3(OH)6 3H2O
    Rarity : Uncommon

Mixite is a bismuth and copper alteration arsenate that is fairly common in the oxidation zone of copper and bismuth deposits. It was named in honor of Anton Mixa, Director of the mines of Joachimsthal (Czech Republic), the locality of discovery. Mixite appears in acicular, striated crystals, often grouped in tufts, rosettes, or encrustations, of millimeter size. More rarely it forms small kidney-shaped masses with a fibrous texture. Its magnificent green to blue-green color is a good distinguishing criterion.

Main photo : Mixite from Hilarion Mine, Lavrion, Greece © Gianfranco Ciccolini

Mixite from Gold Chain Mine, Mammoth, Utah, USA © Alex Earl
Mixite from North Star Mine, Mammoth, Utah, USA © Alex Earl
Mixite from Kaymar, Aveyron, France © William Peraud
Mixite from Cap Garonne, Var, France © Christophe Boutry

Mixite in the World

Mixite is a common, sometimes abundant, mineral in the Tintic mining district of Utah, where the Mammoth mine and its neighbor, the Boss Tweed mine, have yielded the finest known specimens. It is also present in good crystals in Durango (Mexico), it was abundant in the superficial part of the copper veins of Wittichen (Black Forest, Germany). It is also found in Laurion (Greece) and in English Cornwall.

Mixite in France

In France, 15 mm crystals are known at the Roches mine, in Val d'Ajol (Vosges), and in smaller specimens at Cap Garonne (Var). It is also known in Rabejac (Hérault), Kaymar (Aveyron) and in many other deposits.

Twinning

No twin known for this mineral species.

Fakes and treatments

No fakes recorded for this mineral species.


Hardness : 3 to 4
Density : 3.79 to 3.83
Fracture : Undetermined
Streak : Pale bluish-green

TP : Translucent to transparent
RI : 1.743 à 1.830
Birefringence : 0.067
Optical character : Uniaxial +
Pleochroism : Visible
Fluorescence : None

Solubility : -

Magnetism : NoneRadioactivity : None