Wardite
Wardite is NaAl3(PO4)2(OH)4·2H2O, a tetragonal phosphate: hardness 5, density 2.81 to 2.87, perfect {001} cleavage, pseudo-octahedral crystals to 4 cm.
Wardite is a hydrated sodium aluminium phosphate, NaAl3(PO4)2(OH)4·2H2O, first described from the USA in 1896. It is tetragonal, hardness 5, density 2.81 to 2.87, with one perfect {001} cleavage, and forms white to blue-green pseudo-octahedral crystals up to 4 cm, in phosphate nodules and in complex zoned pegmatites.
In short
- Wardite is NaAl3(PO4)2(OH)4·2H2O, grandfathered on the September 2026 IMA-CNMNC Master List with 1896 and the USA. The Handbook of Mineralogy gives two settings: a component of low-temperature phosphatic nodules, and an uncommon species in complex zoned pegmatites.
- Worked from standard atomic weights, the ideal formula gives 35.67% P2O5, 38.43% Al2O3, 7.79% Na2O and 18.11% H2O, the sheet's calculated column exactly. That is 20.34% aluminium by mass, against 19.90% in turquoise and 17.08% in variscite.
- Wardite and turquoise share an Al:P ratio of 3:2 and overlap in density: 2.81 to 2.87 against turquoise's 2.86. Optics and cleavage separate them. Wardite is uniaxial (+) with a perfect {001} cleavage; turquoise is biaxial (+), and its sheet records a fracture but no cleavage.
- The crystals mislead. Wardite is tetragonal, but its dipyramids are pseudo-octahedral, so a well-formed wardite can pass for an octahedron. Striations perpendicular to [001] and the single cleavage give it away.
- Variscite's sheet, in this site's reference set, lists wardite as an associate at the Little Green Monster mine, Clay Canyon, Utah, and wardite's sheet lists variscite there in return. It is the first locality on the wardite sheet.
| Species | Formula | Crystal system | Hardness | Density (meas.) | Cleavage | Optical class | Al by mass |
|---|---|---|---|---|---|---|---|
| Wardite | NaAl3(PO4)2(OH)4·2H2O | Tetragonal | 5 | 2.81 to 2.87 | {001} perfect | Uniaxial (+) | 20.34% |
| Turquoise | CuAl6(PO4)4(OH)8·4H2O | Triclinic | 5 to 6 | 2.86 | None recorded; conchoidal fracture | Biaxial (+) | 19.90% |
| Variscite | AlPO4·2H2O | Orthorhombic | 4.5 | 2.57 to 2.61 | {010} good, {001} poor | Biaxial (−) | 17.08% |
| Faustite | (Zn,Cu)Al6(PO4)4(OH)8·4H2O | Triclinic, by analogy | 5.5 | 2.92 | None recorded; conchoidal fracture | Biaxial (+), by analogy | — |
What is wardite?
A hydrated sodium aluminium phosphate, and a tetragonal one. The Handbook writes NaAl3(PO4)2(OH)4·2H2O and the IMA NaAl3(PO4)2(OH)4(H2O)2: the same composition, with the water written differently. Hardness is 5, measured density 2.81 to 2.87, and there is one perfect cleavage, on {001}.
The crystals are dipyramidal pseudo-octahedral, with {010}, {011}, {012}, {100} and rarely {001}, typically striated ⊥ [001], up to 4 cm. The colour list is long, white, colorless, pale green, blue-green, yellow-green, pale yellow, brown, with a vitreous lustre; in transmitted light it is colourless.
Two relatives are on the IMA list. Fluorowardite, NaAl3(PO4)2(OH)2F2(H2O)2, approved as IMA 2012-016 from the USA, has two of the four hydroxyls replaced by fluorine. Cyrilovite, NaFe3+3(PO4)2(OH)4(H2O)2, grandfathered from 1953 in the Czech Republic, has ferric iron in place of aluminium; one of the references on the wardite sheet is Lindberg's 1957 paper on the relationship of avelinoite, cyrilovite and wardite. Neither has a sheet in this site's reference set, so their properties are not given here.
How much aluminium and phosphorus is in wardite? A worked calculation
Standard atomic weights (Na 22.990, Al 26.982, P 30.974, O 15.999, H 1.008) give NaAl3(PO4)2(OH)4·2H2O a formula mass of 397.934. Expressed as oxides: P2O5 35.67%, Al2O3 38.43%, Na2O 7.79%, H2O 18.11%. Those are the four figures in the sheet's calculated column, to the hundredth, so the formula and the sheet agree. The sheet's analysis, attributed in brackets to the Palermo #1 mine, is close: P2O5 35.12, Al2O3 38.70, Na2O 7.51, H2O 17.88.
As elements: 20.34% aluminium and 15.57% phosphorus. The same method gives turquoise, CuAl6(PO4)4(OH)8·4H2O, 19.90% aluminium and 15.23% phosphorus, and variscite, AlPO4·2H2O, 17.08% and 19.61%. Wardite and turquoise both carry three aluminium for every two phosphorus.
Counted as H2O, 18.11% of the ideal mass is water, held as hydroxyl and as molecular water together, and the sheet puts wardite in low-temperature phosphatic nodules.
How to tell wardite from turquoise and variscite
Density will not separate wardite from turquoise: 2.81 to 2.87 against 2.86. Hardness barely does, 5 against 5 to 6. Variscite is a little lighter and softer, at 2.57 to 2.61 and 4.5.
Crystals and cleavage will. Wardite forms pseudo-octahedral dipyramids up to 4 cm with a perfect {001} cleavage. Turquoise's sheet records rare crystals to 3 mm and a small conchoidal fracture with no cleavage; variscite's, crystals uncommon and to 1.5 mm, a good {010} cleavage. See cleavage or fracture: how to tell. On a refractometer wardite is uniaxial positive and the other two are biaxial.
Colour is the weak test. Wardite's range includes blue-green and pale green, which overlaps turquoise's bluish green and apple-green and variscite's pale green. Blue-green massive phosphate on its own is not wardite; a pseudo-octahedron with a flat cleavage is worth a closer look. For turquoise specifically, see how to tell real turquoise from fake.
Where wardite is found
The sheet's localities: in the USA, the Little Green Monster mine, Clay Canyon, about nine km west of Fairfield, Utah, with variscite, millisite and crandallite; the Dunton quarry and the Bell Pit, Newry, Maine; the Palermo #1 mine, North Groton, New Hampshire; the Hugo pegmatite near Keystone and the Tip Top mine near Custer, South Dakota. Large crystals from the Big Fish River–Rapid Creek area, Yukon. In Brazil, the Lavra da Ilha pegmatite near Taquaral and the Pirineus mine, Itinga, Minas Gerais, and Alto Patrimônio, Paraíba. Also Songo, Sierra Leone; the Wolfsberg quarry near Spittal, Carinthia; Ruffiac and Montebras in France; and in Australia, the Iron Monarch quarry at Iron Knob, Wycheproof in Victoria and Milgun Station in Western Australia. A few other localities are known.
No British locality is on the sheet. In the pegmatites its associates are ferrisicklerite, mitridatite, whitlockite, montgomeryite, fairfieldite, hydroxyl-herderite, eosphorite, siderite and roscherite.
The name honours Henry Augustus Ward (1834–1906), an American collector and dealer in natural history objects, of Ward’s Natural Science Establishment, Rochester, New York. The sheet records no type material. The rest of this reference section is indexed at the species index. There is no catalogue here and nothing here is offered for sale; the wanted list is the only commercial route.