Group of honey-brown jahnsite-(MnMnZn) aggregates with green libethenite blades. Only one sample of Jahnsite-(MnMnZn) was found. The original sample was subdivided into 3 parts, this is one of them. — Photo: Pedro Alves · CC BY 3.0
Jahnsite-(MnMnZn)
Jahnsite-(MnMnZn) is an IMA-recognized mineral species in the phosphate class, with the chemical formula Mn²⁺Mn²⁺Zn₂Fe³⁺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 2.89; White streak; Vitreous to silky luster; optically biaxial.
IMA symbol Jah-MnMnZn, IMA status: approved, named in 2018.
Found in highly altered (leached and silicified) gossan of an iron-manganese deposit.
It is found associated with Zn-bearing libethenite, quartz, rhodochrosite, santabarbaraite.
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.