IANTHINITE

    Class : Oxides and hydroxides
    Subclass : Uranyl hydroxides
    Crystal system : Orthorhombic
    Chemistry : UO2 5UO3 10H2O
    Rarity : Rare

Ianthinite is a rare mineral. It is the only hydrated supergene uranium mineral containing U4+ ion and one of the first pitchblende oxidation minerals. It is found in pitchblende cracks at the limit of the oxidation zone and the primary ore. Unstable, it hydrates very easily in the air and slowly transforms into schoepite. Its name comes from the Greek ianthinos (purple) in reference to its color. Ianthinite forms flattened acicular crystals, purple to reddish brown, of 2 mm at most, commonly grouped in sea urchins, rosettes or felts.

Main photo : Ianthinite partially altered to schoepite from the Clara Mine, Germany © Michael Förch

Ianthinite from Krunkelbach Valley, Germany © Stephan Wolfsried
Ianthinite from Shinkolobwe Mine, Katanga, DR Congo © Uwe Haubenreisser
Ianthinite from Lachaux, Puy-de-Dôme, France © Yannick Vessely
Ianthinite from Rabejac, Hérault, France © Robert Vernet

Ianthinite in the World

Ianthinite, first discovered in Shinkolobwe (Democratic Republic of Congo) has since been encountered in several other localities including the large Canadian deposit of Cluff Lake in Saskatchewan and in Krunkelbach Valley as well as at the Clara Mine (Germany).

Ianthinite in France

In France, ianthinite is known in several French uranium deposits : La Crouzille and Margnac (Haute-Vienne), Bois-Noirs (Loire), Rabejac and Mas d'Alary (Hérault) as well as in Lachaux (Puy-de-Dôme) where it forms tiny but magnificent purplish-brown sea urchins.

Twinning

No twins known for this mineral species.

Fakes and treatments

No fakes recorded for this mineral species.


Hardness : 2 to 3
Density : 5.16
Fracture : Irregular
Streak : Brown, purple

TP : Translucent to transparent
RI : 1.674 to 1.920
Birefringence : 0.246
Optical character : Biaxial -
Pleochroism : Visible
Fluorescence : None

Solubility : -

Magnetism : NoneRadioactivity : Very strong