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.

Wardite from Rapid Creek - Yukon, Canada
Category Phosphate minerals
(repeating unit)
Strunz classification 8.DL.10
Crystal system Tetragonal
Crystal class Trapezohedral (422)
H-M symbol: (4 2 2)
Space group P41212
Unit cell a = 7.03(1), c = 19.04(1) Å;
Z = 4
Color White, colorless, pale green, blue-green, yellow-green, pale yellow, yellow pink.
Crystal habit Dipyramidal pseudo-octahedral crystals, striated; radial, fibrous, encrustations
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]


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, US. Though rare it has been reported from many locations worldwide.

Wardite crystals on matrix

See also


  1. ^ Handbook of Mineralogy
  2. ^ Mindat.org
  3. ^ Webmineral data

This page is based on a Wikipedia article written by authors (here).
Text is available under the CC BY-SA 3.0 license; additional terms may apply.
Images, videos and audio are available under their respective licenses.