WURTZITE

    Class : Sulfides and sulfosalts
    Subclass : Sulfides
    Crystal system : Hexagonal
    Chemistry : ZnS
    Rarity : Quite common

Wurtzite is the hexagonal polymorph of sphalerite and, like it, is of hydrothermal origin. However, it is much less widespread than sphalerite and is mainly found in hydrothermal veins and telescoped deposits in the Andes. As in sphalerite, iron or manganese replace zinc in sometimes significant quantities. It was named in honor of the French chemist Charles Adolphe Wurtz, Professor at the University of Paris. Wurtzite crystals are rare and generally do not exceed 1.5 cm : they are hexagonal pyramids, frequently hemimorphic, sometimes short hexagonal or tabular prisms. Wurtzite commonly consists of fibrous or columnar masses, as well as concentrically banded concretions. Its color is brownish to dark reddish-brown and blackish-brown. It is an occasional ore of zinc.

Main photo : Wurtzite from Merelani Hills, Tanzania © Rob Lavinsky

Wurtzite from Gyöngyösoroszi, Hungary © Bela Feher
Wurtzite from Siglo XX Mine, Potosi, Bolivia © Rock Currier
Wurtzite from Agios Philippos Mine, Greece © Jordy Fabre
Wurtzite from Val Pulita Quarry, Tuscany, Italy © Gianandrea Ghirri

Wurtzite in the World

The best specimens of crystallized wurtzite come from Merelani Hills (Tanzania) and measure up to 5.5 cm, they are red-brown hexagonal prisms. Black hemimorphic prisms of 3 cm are known at Gyöngyösoroszi (Hungary). The so-called "telescoped" deposits of Oruro and Potosi (Bolivia) : Huanuni, Chocaya, Animas, Llallagua have produced interesting crystals. Good crystals have also been extracted from the Romanian mine of Baia Sprie, from Pribram (Czech Republic), and from several American mines (Butte, Montana ; Joplin, Missouri). It also seems widespread in the Australian mines of the Dundas district (Tasmania).

Wurtzite in France

In France, wurtzite is reported at the Rosiers mine near Pontgibaud (Puy-de-Dôme), at St-Jean-de-Maurienne (Savoie), at Chaillac (Indre), at Ste-Marie-aux-Mines (Haut-Rhin) and at Mas d'Alary (Hérault).

Twinning

No twinning known for this mineral species.

Fakes and treatments

No fakes listed for this mineral species.


Hardness : 3.5 to 4
Density : 4 to 4.1
Fracture : Irregular
Streak : Brown

TP : Translucent
RI : 2.356 to 2.378
Birefringence : 0.022
Optical character : Uniaxial +
Pleochroism : None
Fluorescence : None

Solubility : Hydrochloric acid

Magnetism : NoneRadioactivity : None