Jahnsite-(CaFeMg)
Jahnsite-(CaFeMg) is an IMA-recognized mineral species in the phosphate class, with the chemical formula CaFe²⁺Mg₂Fe³⁺₂(PO₄)₄(OH)₂·8H₂O.
It crystallizes in the monoclinic crystal system (space group P2/a). It is a member of the Jahnsite structural group.
Key properties: Mohs hardness 4; specific gravity 2.76; White streak; Vitreous luster; optically biaxial.
IMA symbol Jah-CaFeMg, IMA status: approved, named in 2013.
Found as a secondary mineral in low-grade phosphorites derived by leaching of weakly phosphatic limestones or low-grade primary phosphorites.
It is found associated with Jahnsite-(NaFeMg), goethite, fluorapatite.
The name refers to a jahnsite group mineral with dominant Ca in the X site and Fe2+ and Mg in the M1 and M2 sites.
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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