Billietite- Encyclopedia

    Class : Oxides and hydroxides
    Subclass : Uranyl hydroxide
    Crystal System : Orthorhombic
    Chemistry : Ba(UO2)6O4(OH)6 4H2O
    Rarity : Very rare

Billietite is a very rare mineral from the oxidation zone of uranium deposits. It is a companion of other secondary uranium minerals (especially becquerilite, studtite, fourmarierite...) which, like it, result from the meteoric oxidation of uraninite. However, its formation requires the presence of barium in the rock. In the absence of this element, calcium becquerelite is formed. Its name was given to it in honor of the Belgian crystallographer Valère Louis Billiet. Its crystals are tabular, yellow with pseudohexagonal contours, sometimes elongated.

Main photo : Billietite from Shinkolobwe Mine, Katanga, Democratic Republic of Congo © Uwe Haubenreisser

Twinned billietite from Krunkelback Valley, Freiburg, Germany © Stephan Wolfsried
Billietite from Krunkelback Valley, Freiburg, Germany © Stephan Wolfsried
Billietite from Shinkolobwe Mine, Katanga, D.R. Congo © Gianfranco Ciccolini
Billerite from Rendena Valley, Monte Toff, Italy © Italo Campostrini

Billietite in the World

The best known crystals come from the discovery site, the Shinkolobwe mine, and from the nearby Musonoï deposit (Katanga, Democratic Republic of Congo), they hardly exceed 5 mm. Billietite is also known from several other uranium deposits in Germany and the United States.

Billietite in France

In France, the best crystals of billiétite come from the mines of Margnac II (Haute-Vienne), where it was relatively abundant at the outcrops, from Lodève (Hérault), and from Kruth (Haut-Rhin) from where the best French samples were extracted.

Twinning and special crystallizations

Twins are very common on {110} and {111} resulting in 6 pointed stars.

Fakes and treatments

No fake or treatment recorded for this mineral species.

Hardness : 2 to 3
Density : 5.3
Fracture : Irregular
Trace : Yellow

TP : Translucent to transparent
RI : 1.725 to 1.829
Birefringence : 0.065 to 0.099
Optical character : Biaxial -
Pleochroism : Visible
Fluorescence : Yellow to green

Solubility : -

Magnetism : None
Radioactivity : Very strong