Dufrénite
Dufrénite is an IMA-recognized mineral species in the phosphate class, with the chemical formula Ca₀.₅Fe²⁺Fe³⁺₅(PO₄)₄(OH)₆·2H₂O.
It crystallizes in the monoclinic crystal system (space group C2/c). It is a member of the Dufrénite structural group.
Key properties: Mohs hardness 3.5–4.5; specific gravity 3.1–3.34; Vitreous to silky luster; optically biaxial.
IMA symbol Dfr, grandfathered status — known before the IMA’s founding, named in 1833.
A secondary mineral formed principally in iron ore deposits.
It is found associated with Goethite, beraunite, quartz.
The mineral was named to honor Professor Ours Pierre Armand Petit-Dufrénoy (1792–1857), French mineralogist, National School of Mines, Paris, France.
Index entry. This entry combines official IMA/RRUFF species data with published physical-property data — a full written entry hasn’t been published yet.
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