Groatite
Groatite is an IMA-recognized mineral species in the phosphate class, with the chemical formula NaCaMn₂(PO₄)(HPO₄)₂.
It crystallizes in the monoclinic crystal system (space group C2/c). It is a member of the Alluaudite structural group.
Key properties: Mohs hardness 3; specific gravity 3.213; White streak; Vitreous luster; optically biaxial.
IMA symbol Goa, IMA status: approved, named in 2008.
A late-stage mineral, most likely derived from the dissolution of lithiophosphate and lithiophilite, in a spodumene-rich portion of a zoned petalite-subgroup pegmatite.
It is found associated with Whitlockite, crandallite, an unidentified Na–Al phosphate, quartz.
The mineral was named to honor Lee A. Groat (b. 1959), professor of Mineralogy at the University of British Columbia, Vancouver, British Columbia, Canada.