wardite

{{Infobox mineral | name = Wardite | boxwidth = | boxbgcolor = | image = Wardite.jpg | imagesize = | alt = | caption = Wardite from Rapid Creek – Yukon, Canada | category = Phosphate minerals | formula = NaAl3(PO4)2(OH)4·2(H2O) | IMAsymbol = Wd | molweight = | strunz = 8.DL.10 | dana = | system = Tetragonal | class = Trapezohedral (422) H-M symbol: (4 2 2) | symmetry = 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. | colour = | habit = Dipyramidal pseudo-octahedral crystals, striated; radial, fibrous, encrustations | twinning = | cleavage = Perfect on {001} | fracture = | tenacity = | mohs = 5 | luster = Vitreous | streak = | diaphaneity = Transparent to opaque | gravity = 2.81–2.87 | density = | polish = | opticalprop = Uniaxial (+) | refractive = nω = 1.586 – 1.594 nε = 1.595 – 1.604 | birefringence = δ = 0.009 | pleochroism = | 2V = 0.0 | dispersion = | extinction = | length fast/slow = | fluorescence = | absorption = | melt = | fusibility = | diagnostic = | solubility = | impurities = | alteration = | other = | references = }}

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, with pyramidal {102} or {114} faces and with {001} usually present masses. Also appears as fibrous encrustations. It has a Mohs hardness of 5 and a specific gravity of 2.81–2.87.