Phurcalite - Encyclopedia

    Class : Phosphates, arsenates, vanadates
    Subclass : Uranyl phosphates
    Crystal system : Orthorhombic
    Chemistry : Ca2(UO2)3O2(PO4)2 7H2O
    Rarity : Rare

Phurcalite is a uranium calcium phosphate. It is a secondary mineral of the oxidation zone of uranium deposits, apparently with a predilection for pegmatitic contexts. Its name comes from its chemical composition : phosphorus, uranium and calcium. Phurcalite forms lamellar crystals often united in radiated aggregates, or fine encrustations, of amber yellow to green-yellow color.

Main photo : Phurcalite on quartz from Assunção Mine, Viseu, Portugal © Carlos Gonzalez Bargueño

Phurcalite from Los Azules mine, Atacama, Chile © Gianfranco Ciccolini
Phurcalite from Bois Noirs, Loire, France © Pascal Chollet
Phurcalite from Posey Mine, Utah, USA © Alex Earl
Phurcalite from Boucheron, Davignac, Corrèze, France © Enrico Bonacina

Phurcalite in the World

The most beautiful crystallizations of phurcalite come from Perus (Sao Paulo, Brazil), a deposit which produced lamellar crystals reaching 5 mm grouped in radiated aggregates. Phurcalite is also known in several polymetallic uranium and pegmatite veins in Germany (Wittichen, Bergen, Hagendorf), in several American uranium deposits, and in the Shinkolobwe deposit (Katanga, Democratic Republic of Congo).

Phurcalite in France

In France, it is reported in Davignac, near Meymac (Corrèze) as well as in Bois Noirs (Loire).

Twinning

No twins known for this mineral species.

Fakes and treatments

No fakes listed for this mineral species.


Hardness : 3
Density : 4.22
Fracture : Conchoidal
Streak : Pale yellow

TP : Translucent to transparent
RI : 1.660 to 1.749
Birefringence : 0.059
Optical character : Biaxial -
Pleochroism : Strong
Fluorescence : Green

Solubility : -

Magnetism : NoneRadioactivity : Very strong