CORKITE

    Class : Phosphates, arsenates, vanadates
    Subclass : Anhydrous phosphates
    Crystal system : Rhombohedral
    Chemistry : PbFe3(PO4)(SO4)(OH)6
    Rarity : Uncommon

Corkite is a complex phosphate of iron and lead comprising frequent groups (SO4) replacing groups (PO4), which leads some authors to consider it as a sulphate. It is a secondary mineral formed in the supergene oxidation zone of hydrothermal base metal deposits, where it accompanies many secondary base metal minerals, notably lead (cerussite, pyromorphite, etc...). It owes its name to its location of discovery : the Glandore iron mine in County Cork (Ireland). It forms pseudocubic rhombohedral crystals not exceeding 2 mm, and aggregates or powdery crusts of pale yellow, pale green to dark green or sometimes yellow-brown to brown.

Main photo : Corkite from Schöne Aussicht Mine, Germany © Christian Rewitzer

Corkite from Glandore Mine, Ireland © Ru Smith
Corkite from Schöne Aussicht Mine, Germany © Stephan Wolfsried
Corkite from Schöne Aussicht Mine, Germany © Marko Burkhardt
Corkite from Échassières, Allier, France © Yannick Vessely

Corkite in the World

The Caldbeck Fells mine (Cumberland, England) yielded 2 mm pseudo-octahedral crystals considered to be the best known. The oxidized zone of the iron mines of Glandore (Ireland) gave the first crystals of this mineral, also well known in quite a few German, American and Mexican mines.

Corkite in France

In France, corkite is known at Échassières (Allier), at Bois de Buzon (Nièvre), at the La Lande quarry (Morbihan), at Kaymar (Aveyron), at Vigan (Gard) as well as at La Fumade (Tarn).

Twinning

No twin known for this mineral species.

Fakes and treatments

No fake identified for this mineral species.


Hardness : 3.5 to 4.5
Density : 4.29
Fracture : -
Streak : -

TP : Transparent to translucent
RI : 1.93 to 1.96
Birefringence : 0.030
Optical character : Uniaxial -
Pleochroism : None
Fluorescence : None

Solubility : Hydrochloric acid


Magnetism : None
Radioactivity : None