Dark green to black tarnished cleavable alluaudite mass with white quartz. Pleasant Valley pegmatite, Fourmile, Custer County, South Dakota. (Photo by W. Cordua.)

Formula: (Na,Ca)Mn2+(Mn,Fe3+,Fe2+,Mg)2(PO4)3 Monoclinic


This is a series of rare phosphate minerals found in granite pegmatites.

FLORENCE COUNTY: Described as a component of tan to light brown phosphate nodules associated with apatite, heterosite-purpurite and schorl in the south end of a complexly zoned pegmatite in Florence County (Falster, Simmons and Moore, 1988).