KRÖHNKITE

    Class : Sulfates, chromates, molybdates
    Subclass : Hydrated sulfates
    Crystal system : Monoclinic
    Chemistry : Na2Cu(SO4)2 2H2O
    Rarity : Very rare

Kröhnkite (or kroehnkite) is a very rare sulfate from the oxidation zone of copper deposits, associated with chalcanthite, antlerite and other copper salts. It was named in honor of B. Kröhnke who was the first to analyze the mineral. Krohnkite forms stubby, sometimes pseudo-octahedral prismatic crystals, encrustations and fibrous veinlets that are light blue to dark blue in color, fading to blue-green to yellowish green in light. It was locally an important copper ore.

Main photo : Kröhnkite from Chuquicamata Mine, Chile © Rob Lavinsky

Kröhnkite from Chuquicamata Mine, Chile © Gordon De' Young
Kröhnkite from La Compañia Mine, Chile © Gianfranco Ciccolini
Kröhnkite & antlerite from Chuquicamata Mine, Chile © Shann Young
Kröhnkite from Golosina Mine, Andalusia, Spain © Christian Rewitzer

Kröhnkite in the World

Kröhnkite is an extremely rare secondary mineral discovered in two deposits in northern Chile : Chuquicamata, where it was an important copper ore and where the prismatic crystals exceeded 5 cm, and the mine near Salvador, near Quetena. It is known from around ten deposits around the world.

Kröhnkite in France

Kröhnkite is not known in the French underground.

Twinning

Twins are known on {101} sometimes forming hearts.

Fakes and treatments

No fakes recorded for this mineral species.


Hardness : 2.5 to 3
Density : 2.90
Fracture : Conchoidal
Streak : White

TP : Translucent to transparent
RI : 1.544 to 1.601
Birefringence : 0.057
Optical character : Biaxial -
Pleochroism : None
Fluorescence : None

Solubility : Water

Magnetism : NoneRadioactivity : None