Brownish crystal aggregates of the rare member rof the pumpellyite group, pumpellyite-(Mn) from Liguria, Italy (Cassagna Mine, Genova Province, Liguria, Italy). Ex. Erich Laskowski collection (USA). — Photo: David Hospital · CC BY 4.0
Pumpellyite-(Mn2+)
The divalent-manganese member of the pumpellyite sorosilicate series — a mineral of low-grade metamorphic rocks.
Intro adapted from Wikipedia (CC BY-SA).
Pumpellyite-(Mn2+) is an IMA-recognized mineral species in the silicate class, with the chemical formula Ca₂Mn²⁺Al₂(Si₂O₇)(SiO₄)(OH)₂·H₂O.
It crystallizes in the monoclinic crystal system (space group A2/m). It is a member of the Pumpellyite structural group.
Key properties: Mohs hardness 5; specific gravity 3.34; Light grayish pink streak; Vitreous luster; optically biaxial.
IMA symbol Pmp-Mn2+, IMA status: approved, named in 1980.
Found in braunite ore in a syngenetic bedded manganese deposit developed in low-grade metamorphic rocks.
It is found associated with Braunite, piemontite, clinozoisite, caryopilite, johannsenite, rhodochrosite, albite, quartz, calcite.
The name refers to its membership in the pumpellyite group and dominant manganous manganese content.