Wavellite

Wavellite

Wavellite cluster from Saline County, Arkansas (size: 4.5 x 4.2 x 3.6 cm)
General
Category Phosphate minerals
Formula
(repeating unit)		 Al3(PO4)2(OH,F)3·5H2O
Strunz classification 8.DC.50
Crystal system Orthorhombic
Crystal class Dipyramidal (mmm)
H-M symbol: (2/m 2/m 2/m)
Space group Pcmn
Unit cell a = 9.621 Å
b = 17.363 Å,
c = 6.994 Å; Z = 4
Identification
Color Green to yellowish-green and yellow, brown, white and colorless
Crystal habit Spherical, radial aggregates; striated prisms; crusty to stalactitic
Cleavage [110] perfect, [101] good, [010] distinct
Fracture Uneven to subconchoidal
Mohs scale hardness 3.5 - 4
Luster Vitreous to resinous, pearly
Streak White
Diaphaneity Translucent
Specific gravity 2.36
Optical properties Biaxial (+)
Refractive index nα = 1.518 - 1.535 nβ = 1.524 - 1.543 nγ = 1.544 - 1.561
Birefringence δ = 0.026
Pleochroism Weak; X = greenish; Z = yellowish
2V angle Measured: 60° to 72°
Fusibility Infusable, swells and splits on heating
Solubility Insoluble
References [1][2][3][4]

Wavellite is a phosphate mineral with formula Al3(PO4)2(OH, F)3·5H2O. It normally occurs as translucent green radial or spherical clusters.

Discovery and occurrence

Wavellite from the Avant Mine, Garland County, Arkansas, showing spherical structure (size: 3.4 x 2.0 x 1.1 cm)

It was first described in 1805 for an occurrence within the High Down Quarry, Filleigh, Devon, England and named for William Wavell (20 December 1750 - 15 January 1829) of England who discovered the mineral.[3]

It occurs in association with crandallite and variscite in fractures in aluminous metamorphic rock, in hydrothermal regions and in phosphate rock deposits.[1] It is found in a wide variety of locations notably in the Mount Ida, Arkansas area in the Ouachita Mountains.

It is sometimes used as a gemstone.[5]

See also

References

  1. 1 2 Handbook of Mineralogy
  2. ↑ Webmineral
  3. 1 2 Mindat
  4. ↑ Klein, Corneis and Cornelius S. Hurlbut, Jr., Manual of Mineralogy, Wiley, 20th ed. 1985, p. 362-3 ISBN 0-471-80580-7
  5. ↑ Gemstones: Properties, Identification and Use By Arthur Thomas, p.132
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