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
CategoryPhosphate minerals
(repeating unit)
Strunz classification8.DL.10
Crystal systemTetragonal
Crystal classTrapezohedral (422)
H-M symbol: (4 2 2)
Space groupP41212
Unit cella = 7.03(1), c = 19.04(1) Å;
Z = 4
ColorWhite, colorless, pale green, blue-green, yellow-green, pale yellow, yellow pink.
Crystal habitDipyramidal pseudo-octahedral crystals, striated; radial, fibrous, encrustations
CleavagePerfect on {001}
Mohs scale hardness5
DiaphaneityTransparent to opaque
Specific gravity2.81 - 2.87
Optical propertiesUniaxial (+)
Refractive indexnω = 1.586 - 1.594 nε = 1.595 - 1.604
Birefringenceδ = 0.009
2V angle0.0


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

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