DERRIKSITE

    Class : Oxides et hydroxides
    Subclass : Uranyl selenites
    Crystal system : Orthorhombic
    Chemistry : Cu4(UO2)(SeO3)2(OH)6
    Rarity : Very rare

The appearance of derreksite and other uranium selenites requires the joint presence of sufficient quantities of selenium and uranium in the same deposit. These conditions are only met exceptionally, which explains the great rarity of these minerals, only four in number (guilleminite, demesmaekerite, derriksite and marthozite), and their presence in only two deposits. It was named in honor of the Belgian geologist Joseph Derriks who studied the Shinkolobwe uranium deposits in Katanga. Derricksite forms small automorphic crystals not exceeding 0.7 mm, elongated or tabular, green to bottle green in color. Like demesmaekerite and guilleminite, it appears essentially in microcrystalline crusts on a seleniferous digenite which provided the selenium necessary for the formation of uranyl selenites.

Main photo : Derriksite from Musonoi Mine, Kolwezi, Mutshatsha, Lualaba, D.R. Congo © Christophe Boutry

Derriksite in the World

It is known in the oxidation zone of the Musonoï copper and cobalt deposit (Democratic Republic of Congo) which provided the best specimens. Selenium comes from the alteration of a seleniferous digenite and uranium from the dissolution of rare uranium minerals. It is also found in Zálesí (Czech Republic).

Photo on the right : Derriksite from Musonoi Mine, Kolwezi, Mutshatsha, Lualaba, D.R. Congo © Leon Hupperichs

Derriksite in France

Demesmaekerite is not present in the French underground.

Twinning

No twin known for this mineral species.

Fakes and treatments

No fakes listed for this mineral species.


Hardness : 4
Density : 4.61
Fracture : Undetermined
Streak : Green

TP : Translucent
RI : 1.770 to 1.890
Birefringence : 0.120
Optical character : Biaxial -
Pleochroism : Visible
Fluorescence : None

Solubility : -


Magnetism : None
Radioactivity : Strong

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