Oxo-mangani-leakeite
Oxo-mangani-leakeite is an IMA-recognized mineral species in the silicate class, with the chemical formula NaNa₂(Mn³⁺₄Li)Si₈O₂₂O₂.
It crystallizes in the monoclinic crystal system (space group C2/m). It is a member of the Amphibole structural group.
Key properties: Mohs hardness 6; specific gravity 3.25; Vitreous luster; optically biaxial.
IMA symbol Omlk, IMA status: approved, named in 2015.
Found in the oxidized portions of a manganese deposit, most likely a metamorphosed (upper middle to middle greenschist facies) submarine exhalative deposit.
It is found associated with Namansilite, aegirine, manganoan pectolite-serandite, braunite, norrishite, calcium and barium carbonates, quartz, albite, potassium feldspar.
Signifies an amphibole in the compositional range of leakeite with dominant manganese in the C structural site and dominant oxygen in the W site.