Messelite Locality: Messel Mine, Messel, Darmstadt, Hesse, Germany Field of view 2.5 cm — Photo: Leon Hupperichs · CC BY-SA 3.0
Messelite
A hydrated calcium-iron-manganese phosphate — discredited in 1940, reinstated in 1955, name restored in 1959.
Intro adapted from Wikipedia (CC BY-SA).
Messelite is an IMA-recognized mineral species in the phosphate class, with the chemical formula Ca₂Fe²⁺(PO₄)₂·2H₂O.
It crystallizes in the triclinic crystal system (space group P-1). It is a member of the Fairfieldite structural group.
Key properties: Mohs hardness 3.5; specific gravity 3.16; Vitreous luster; refractive index 1.659; optically biaxial.
IMA symbol Msl, IMA status: approved, named in 1890.
Principally as a late stage hydrothermal alteration product in zoned complex granite pegmatites.
It is found associated with Triphylite, anapaite, vivianite, ludlamite, siderite, goyazite, whitlockite, herderite, amblygonite, eosphorite, brazilianite, graftonite, fairfieldite.
The name refers to the locality from which the first specimens were obtained, Messel, Germany.