Natrophilite , Lithiophilite Locality: Abija N. Fillow Quarry (Branchville Quarry), Branchville , Redding , Fairfield County, Connecticut , USA ( Locality at mindat.org ) Size: 3.7 x 2.2 x 1.9 cm. A rare phosphate, from the type locality circa late 1800s. The natrophilite appears on the back of the specimen (see closeup view). Ex. G.J. Brush collection at Yale, so this was considered an important enough representative example that the Academy had to trade for it, to get the species. The presence of natrophilite as thin coatings and fracture fillings has been verified by Dr. Mark Feinglos. Further examination by Dr. Feinglos revealed the presence of lithiophilite and metaswitzerite, as well. Ex. Philadelphia Academy of Sciences Collection. — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Natrophilite
A yellow sodium-manganese phosphate forming transparent orthorhombic crystals in pegmatites.
Intro adapted from Wikipedia (CC BY-SA).
Natrophilite is an IMA-recognized mineral species in the phosphate class, with the chemical formula NaMn²⁺(PO₄).
It crystallizes in the orthorhombic crystal system (space group Pnam). It is a member of the Olivine structural group.
Key properties: Mohs hardness 4.5–5; specific gravity 3.41; Bright resinous to nearly adamantine, somewhat pearly on the {001} cleavage luster; optically biaxial.
IMA symbol Ntp, grandfathered status — known before the IMA’s founding, named in 1890.
A rare mineral, replacing lithiophilite, in a complex granite pegmatite.
It is found associated with Lithiophilite, triploidite, eosphorite, huréaulite, fairfieldite, dickinsonite.
The name refers to its content of sodium, natrium, and from the Greek for a friend.