DUFRENITE

    Class : Phosphates, arsenates, vanadates
    Subclass : Hydrated phosphates
    Crystal system : Monoclinic
    Chemistry : Ca0.5Fe6(PO4)4(OH)6 2H2O
    Rarity : Quite common

Dufrenite is a hydrated iron phosphate of secondary origin. It is mainly found in sodolithic pegmatites as a primary phosphate alteration mineral (notably triphylite). It is also a mineral associated with limonite in gossans of sulphide veins and sedimentary iron deposits. It was named in honor of Pierre Armand Dufrénoy, professor at the Paris School of Mines. Dufrenite is black to dark brown, or dark olive green. The crystals are rare, tabular, and do not exceed a millimeter ; they are sometimes assembled in rosettes or subparallel aggregates. Dufrenite occurs mainly in spherules, encrustations and botryoidal masses with a fibroradiated texture. The fibers do not exceed one centimeter.

Main photo : Dufrenite from Echassières, Allier, France © Pascal Chollet

Dufrenite from Hoff auf mich Mine, Germany © Eugene & Sharon Cisneros
Dufrenite from Bel Air Mine, Mauléon, Deux-Sèvres, France © Jean-Marc Johannet
Dufrenite from Echassières, Allier, France © Pascal Chollet
Dufrenite from Echassières, Allier, France © Pascal Chollet

Dufrenite in the World

The Hagendorf quarry (Bavaria, Germany) provided excellent specimens of dufrenite, as did the famous American phosphate pegmatites of Palermo and Tip-Top (New Hampshire) and the English mine of Wheal Phoenix, near Linkinhome. (Cornwall).

Dufrenite in France

In France, the ancient oolitic iron deposit of Pluherlin (Morbihan) provided beautiful centimeter-sized spherolites composed of bottle green crystals. It is also reported at Echassières (Allier), at Montebras (Creuse), at Mauléon (Deux-Sèvres), at Bessines-sur-Gartempe and Compreignac (Haute-Vienne) as well as in the pegmatites of Collioure (Pyrénées-Orientales).

Twinning

No twin known for this mineral species.

Fakes and treatments

No fake listed for this mineral species.


Hardness : 3.5 to 4.5
Density : 3.1 to 3.34
Fracture : Fibrous
Streak : Green

TP : Translucent to opaque
RI : 1.820 to 1.925
Birefringence : 0.055 to 0.083
Optical character : Biaxial (+/-)
Pleochroism : Visible
Fluorescence : None

Solubility : Nitric acid and hydrochloric acid


Magnetism : None
Radioactivity : None

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