The open encyclopedia of minerals
GlossaryCite the database
Mineralogist.org
Minerals A–ZSearchCollectionsBrowse by PropertyIdentify a SpecimenCompare MineralsLocalities MapGlossaryContribute Search the Database →
Phosphate

Jahnsite-(MnMnMg)

Mn²⁺Mn²⁺Mg₂Fe³⁺₂(PO₄)₄(OH)₂·8H₂O
Hardness4
Crystal systemMonoclinic
ClassPhosphate
←PrevJahnsite-(MnMnFe)NextJahnsite-(MnMnMn)→
Jahnsite-(MnMnMg) specimen

Jahnsite-(MnMnMg) from Sapucaia mine, Sapucaia do Norte, Galiléia, Minas Gerais, Brazil. — Photo: Sergio Varvello · CC0

Jahnsite-(MnMnMg)

Jahnsite-(MnMnMg) is an IMA-recognized mineral species in the phosphate class, with the chemical formula Mn²⁺Mn²⁺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 2.625; Very pale yellow streak; Vitreous luster; optically biaxial.

IMA symbol Jah-MnMnMg, IMA status: approved, named in 2018.

A late-stage alteration product of primary triphylite in a metasomatic unit of zoned granitic pegmatite.

It is found associated with Frondelite, leucophosphite, mangangordonite, ferrisicklerite.

Root name, jahnsite, indicates a member of the group with M(3) = Fe3+; the suffix indicates sequentially the dominant atom in the X, M(1), and M(2) structural positions.

Index entry. This entry combines official IMA/RRUFF species data with published physical-property data — a full written entry hasn’t been published yet. Browse more J minerals or help write this entry.