Phosphophyllite Locality: Unificada Mine, Cerro de Potosí (Cerro Rico), Potosí City, Potosí Department, Bolivia (Locality at mindat.org) Size: small cabinet, 6. — Photo: Robert M. Lavinsky · CC BY-SA 3.0
Phosphophyllite
A zinc-iron phosphate famed for its delicate blue-green crystals — a prized but rarely cut collector's gem.
Intro adapted from Wikipedia (CC BY-SA).
Phosphophyllite is an IMA-recognized mineral species in the phosphate class, with the chemical formula Zn₂Fe²⁺(PO₄)₂·4H₂O.
It crystallizes in the monoclinic crystal system (space group P2_1/c). It is a member of the Phosphophyllite structural group.
Key properties: Mohs hardness 3–3.5; specific gravity 3.08–3.13; typically blue or green; white streak; Vitreous luster; refractive index 1.605; optically biaxial.
IMA symbol Pp, grandfathered status — known before the IMA’s founding, named in 1920.
Typically a secondary mineral in zoned complex granite pegmatites, an alteration product of sphalerite and Fe–Mn phosphates; in hydrothermal vein deposits.
It is found associated with Triplite, triphylite, sphalerite, apatite, vivianite, rockbridgeite, strengite, phosphosiderite, fairfieldite (Hagendorf, Germany).
The name comes from phosphate in the composition, and the Greek for cleavage.
Collections: Collector Favorites, Rare & Remarkable, Gemstones.