Formula: Ca0.5Fe2+Fe3+5(PO4)4(OH)6.2H2O
Hydrated phosphate containing hydroxyl, forms series with burangaite and with natrodufrénite
Specific gravity: 3.1 to 3.34
Hardness: 3½ to 4½
Streak: Green
Colour: Dark green, olive-green, olive-brown, black; olive-brown to reddish brown with oxidation; bluish green to reddish brown or yellow in transmitted light Mindat
Solubility: Soluble in dilute acids.

Pegmatites rarely
Sedimentary environments

Dufrénite is a secondary mineral occuring with limonite in gossans and in iron ore deposits (Dana, Mindat) associated with goethite, beraunite, quartz, cacoxenite, siderite and strengite (Mindat, HOM).

At Kintore, Broken Hill, New South Wales, Australia, dufrénite occurs on quartzite or garnet sandstone associated with leucophosphite and chalcosiderite (AJM 3.1.46).

At the Moculta Phosphate Quarry, Angaston, Barossa Valley, Mount Lofty Ranges, South Australia, dufrénite is associated with rockbridgeite (AJM 17.1.23-24).

At the Fairview Quarry, Robertstown, Mount Lofty Ranges, South Australia, dufrénite is associated with wavellite and cyrilovite (AJM 17.1.23-24).

At the Mount Deverell variscite deposit, Milgun Station, Western Australia, dufrénite has been found on fracture surfaces associated with goethite. The variscite deposits are hosted by marine sedimentary rocks (AJM 20.2.24).

At the co-type localities, Anglar, Haute-Vienne, Nouvelle-Aquitaine, France, and the Hoff auf mich Mine, Ullersreuth, Thuringia, Germany, dufrénite occurs in an iron ore deposit associated with strengite, goethite and cacoxenite (Mindat).

In Cornwall, England, dufrénite has been found as crystals superficially altered to oxy-hydroxides and associated with pharmacosiderite in a fractured quartz vein (AM 55.135-169).

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