Phosphophyllite

Phosphophyllite is a rare phosphate mineral with the chemical formula Zn₂Fe(PO₄)₂·4H₂O. It is prized among mineral collectors for its delicate bluish green colour, but rarely cut for its difficult properties.

Phosphophyllite
General
Category	Phosphate minerals
Formula	Zn2Fe(PO4)2·4H2O
IMA symbol	Pp[1]
Strunz classification	8.CA.40
Crystal system	Monoclinic
Crystal class	Prismatic (2/m) (same H-M symbol)
Space group	P21/c
Identification
Formula mass	448.40 g/mol
Color	Blue-green to colourless
Crystal habit	Prismatic
Twinning	Common
Cleavage	[100] Perfect, [010] Distinct, [102] Distinct
Fracture	Conchoidal
Mohs scale hardness	3.5
Luster	Vitreous
Streak	White
Diaphaneity	Transparent
Specific gravity	3.1
Optical properties	Biaxial (−)
Refractive index	nα = 1.595–1.599, nβ = 1.614–1.617, nγ = 1.616–1.620
Birefringence	0.021
2V angle	Measured 44°, Calculated 34°
Common impurities	Manganese
References	[2]

Geology

Phosphophyllite was first described in 1920 by Heinrich Laubmann and Hermann Steinmetz.^[3] The name derives from from Ancient Greek phyllon 'leaf', and phosphate^[4]

Chemically, phosphophyllite is related to zinc phosphate with some zinc substituted by iron. Phosphophyllite has been synthesized by the addition of diammonium phosphate to a solution of zinc and iron sulfate.^[5]

Occurrence

The finest phosphophyllite crystals come from Potosí, Bolivia, but it is no longer mined there. Other sources include New Hampshire, United States and Hagendorf, Bavaria, Germany. It is often found in association with the minerals chalcopyrite and triphylite.^[6]

Uses

Phosphophyllite is highly prized by collectors for its rarity and for its delicate bluish green colour but brittleness and fragility as well as the intrinsic value of large crystals make it unsuitable for jewelry.^[7]

Gallery

Twinned phosphophyllite, Unificada Mine, Cerro de Potosí, Potosí Department, Bolivia. 2.1 × 1.4 × 1 cm

Popular culture

An anthropomorphic form of phosphophyllite is the protagonist of the manga and anime series Land of the Lustrous, with key features of the mineral such as its brittle nature and vibrant color reflected in their character traits and design.^[8]