Perhamite Locality: Emmons Quarry (Uncle Tom Mt. Quarry), Uncle Tom Mt, Greenwood , Oxford County, Maine , USA ( Locality at mindat.org ) Size: 5.0 x 3.7 x 1.8 cm. A plate of feldspar featuring perhamite in spherical crystals aggregates upon the feldspar. The whole matrix is coated by a micro-layer of sparkly apatite druse. — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Perhamite
A rare calcium-aluminium silicophosphate found as millimetre hexagonal plates in amblygonite pegmatites.
Intro adapted from Wikipedia (CC BY-SA).
Perhamite is an IMA-recognized mineral species in the silicate class, with the chemical formula Ca₃Al₇.₇Si₃P₄O₂₃.₅(OH)₁₄.₁·8H₂O.
It crystallizes in the hexagonal crystal system (space group P-3m1). It is a member of the Perhamite structural group.
Key properties: Mohs hardness 5; specific gravity 2.64; White streak; Dull, vitreous on cleavage surface luster; optically uniaxial.
IMA symbol Phm, IMA status: approved, named in 1975.
Occurs as isolated masses in a vuggy, amblygonite-rich pegmatite (Bell Pit, Maine, USA).
It is found associated with Siderite, wardite, amblygonite, eosphorite, sphalerite (Bell Pit, Maine, USA); fluellite, minyulite, wavellite (Tom's quarry, South Australia).
The mineral was named to honor Frank Croydon Perham (b. 1934), American geologist and pegmatite miner of West Paris, Maine, USA.