Dufrenite - Encyclopedia
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 in the World
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