Fairfieldite Locality: Foote Lithium County Mine (Foote Mine), Kings Mountain District, Cleveland County, North Carolina , USA ( Locality at mindat.org ) Classic old material ! To find a Fairfieldite up to 1 cm is truly rare, but give it good definition, luster, and color as the largest crystal has here and you have a truly significant specimen. 2.9 x 2.5 x 1.5 cm — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Fairfieldite
Fairfieldite is an IMA-recognized mineral species in the phosphate class, with the chemical formula Ca₂Mn²⁺(PO₄)₂·2H₂O.
It crystallizes in the triclinic crystal system (space group P-1). It is a member of the Fairfieldite structural group.
Key properties: Mohs hardness 3.5; specific gravity 3.08–3.11; White streak; Pearly to subadamantine, vitreous on the {001} cleavage luster; optically biaxial.
IMA symbol Ffd, grandfathered status — known before the IMA’s founding, named in 1879.
An accessory mineral in granite pegmatites.
It is found associated with Apatite, strunzite, diadochite, dickinsonite, stewartite, rockbridgeite, mitridatite, eosphorite, a host of other Fe–Mn phosphates, jahnsite, rhodochrosite.
The name refers to Fairfield Co., Connecticut, USA, within which is Branchville, the original locality.