UMOHOITE

    Class : Sulfates, chromates, molybdates
    Subclass : Uranyl molybdates
    Crystal system : Monoclinic
    Chemistry : (UO2)MoO4 4H2O
    Rarity : Very rare

Representative of an extremely rare category of minerals, uranyl molybdates. It fills thin veinlets or draws small areas scattered in the alteration zone of uranium deposits. Note that, unlike vanadium, molybdenum only forms very rare supergene minerals with uranium ; only nine species are known to date, three of which are present in France. Its name comes from its chemical composition : uranium, molybdenum and water. Umohoite occurs in flattened crystals or microcrystalline aggregates, with a lamellar or foliated appearance, and a bright red or green color.

Main photo : Umohoite from Rabejac, Lodève, Hérault, France © Joy Desor

Umohoite in the World

Discovered in the Marysvale uranium deposit (Utah) in 1958, umohoïte has since been recognized in about ten uranium deposits around the world, including the famous Shinkolobwe mine (Katanga), where it encrustes molybdenite.

Right photo : Umohoite from Kyzylsai Mo-U deposit, Kazakhstan © Pavel Kartashov


Umohoite in France

In France, umohoïte forms small spherules of a magnificent red hue at Rabejac and Mas d'Alary in the Lodève uranium basin (Hérault).

Twinning

No known twinning for this mineral species.

Fakes and treatments

No fakes listed for this mineral species.


Hardness : 2
Density : 4.53 to 4.66
Fracture : Undetermined
Streak : Undetermined

TP : Translucent
RI : 1.660 to 1.915
Birefringence : 0.255
Optical character : Biaxial -
Pleochroism : Visible
Fluorescence : None

Solubility : -

Magnetism : NoneRadioactivity : Strong

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