Beraunite - Encyclopedia

    Class : Phosphates, arsenates, vanadates
    Subclass : Hydrated phosphates
    Crystal System : Monoclinic
    Chemistry : Fe6(PO4)4(OH)5 6H2O
    Rarity : Uncommon

Beraunite is an hydrated iron phosphate of secondary origin that forms by weathering of primary phosphates, including triphylite and lithiophyllite, in granitic pegmatites and some iron deposits. It owes its name to its place of discovery : the Hrbek mine, near Beraun (Czech Republic). It occurs in slightly elongated tabular crystals of 1 cm at most, often united in fibroradiated or spherulitic aggregates, or in discoid concretions. It is a dark greenish to dark greenish brown mineral when fresh, then dulls and opacifies in light to dark reddish to reddish brown hues.

Main photo : Beraunite from Indian Mountain, Alabama, USA © Henry Barwood

Beraunite from Rotläufchen Mine, Germany © Marko Burkhardt
Beraunite from Gutglück Mine, Germany © Marko Burkhardt
Beraunite from Regada, Viseu, Portugal © Gianfranco Ciccolini
Beraunite from La Fumade, Tarn, France © Jean-Marc Johannet

Beraunite in the World

Beraunite is not uncommon in phosphate pegmatites. It is particularly known in fine specimens in those of Hagendorf near Pleystein and Rabenstein, in Bavaria (Germany), but also in Palermo and Fletcher (New Hampshire), Keystone and Custer (South Dakota), Foote (North Carolina ) and in Mangualde (Portugal). It also exists in the iron deposits of the Giessen region (Germany), and in imposing masses partially transforming the gigantic vivianite crystals of Anloua (Cameroon).

Beraunite in France

In France, beraunite has been described in Montmins (Allier), at the Lande quarry (Morbihan), at the Vilatte quarry (Haute-Vienne), in the pegmatites of Collioure (Pyrénées-Orientales) and at La Fumade (Tarn).

Twinning and special crystallizations

Twins are known on {100}.

Fakes and treatments

No fake or treatment identified for this mineral species.

Hardness : 3 to 4
Density : 2.8 to 3
Fracture : Irregular
Trace : Green to yellow

TP : Translucent
RI : 1.707 to 1.820
Birefringence : 0.031
Optical character : Biaxial +
Pleochroism : Visible
Fluorescence : None

Solubility : Hydrochloric acid

Magnetism : None
Radioactivity : None