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Formula:
Ca0.5Fe2+Fe3+5(PO4)4(OH)6.2H2O
Hydrated phosphate, dufrénite group, forms series with
burangaite and with
natrodufrénite
Crystal System: Monoclinic
Specific gravity: 3.1 to 3.34 measured, 3.41 calculated
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.
Environments
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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