Kröhnkite - Encyclopedia
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 in the World
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