Wardite

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Wardite
Wardite.jpg
Wardite from Rapid Creek - Yukon, Canada
General
Category Phosphate minerals
Formula
(repeating unit)
NaAl3(PO4)2(OH)4·2(H2O)
Strunz classification 08.DL.10
Crystal symmetry Tetragonal trapezohedral
H-M symbol: (4 2 2)
Space group: P 41212
Unit cell a = 7.03(1) Å, c = 19.04(1) Å;
Z = 4
Identification
Color White, colorless, pale green, blue-green, yellow-green, pale yellow, yellow pink.
Crystal habit Dipyramidal pseudo-octahedral crystals, striated; radial, fibrous, encrustations
Crystal system Tetragonal
Cleavage Perfect on {001}
Mohs scale hardness 5
Luster Vitreous
Diaphaneity Transparent to opaque
Specific gravity 2.81 - 2.87
Optical properties Uniaxial (+)
Refractive index nω = 1.586 - 1.594 nε = 1.595 - 1.604
Birefringence δ = 0.009
2V angle 0.0
References [1][2][3]

Wardite is a hydrous sodium aluminium phosphate hydroxide mineral with formula: NaAl3(PO4)2(OH)4·2(H2O). Wardite is of interest for its rare crystallography. It crystallizes in the tetragonal trapezohedral class and is one of only a few minerals in that class. Wardite forms vitreous green to bluish green to white to colorless crystals, masses, and fibrous encrustations. It has a Mohs hardness of 5 and a specific gravity of 2.81–2.87.

Occurrence[edit]

It occurs with variscite in phospatic nodules and occurs uncommonly in pegmatites and phosphate deposits through alteration of amblygonite.

Wardite was named for Henry Augustus Ward (1834–1906) of the University of Rochester in New York. It first described in 1896 for an occurrence in Clay Canyon, Fairfield, Utah County, Utah, USA. Though rare it has been reported from many locations worldwide.

Wardite crystals on matrix

See also[edit]

References[edit]