Outstanding green crystals of the very rare Mn-V mineral momoite from the famous Gambatesa mine (Valgraveglia Mine, Reppia, Ne, Graveglia Valley, Genova Province, Liguria, Italy). Ex Vandenbroucke Museum collection from Waregem, Belgium. — Photo: David Hospital · CC BY-SA 4.0
Momoiite
Momoiite is an IMA-recognized mineral species in the silicate class, with the chemical formula Mn²⁺₃V³⁺₂(SiO₄)₃.
It crystallizes in the cubic crystal system (space group Ia-3d). It is a member of the Garnet structural group.
Key properties: Mohs hardness 6.5; specific gravity 4.01; Dull green streak; Vitreous luster.
IMA symbol Mom, IMA status: approved, named in 2009.
Product of the metamorphism of siliceous manganese-bearing rocks.
It is found associated with Rhodonite, calcite, tephroite, goldmanite, spessartine, vuorelainenite (Kurase mine); rhodonite, tephroite, celsian, rhodochrosite.
The mineral was named to honor Hitoshi Momoi (1930-2002), who first recognized Mn3V2Si3O12 molecules in garnet.