Wavellite cluster from Saline County, Arkansas (size: 4.5 x 4.2 x 3.6 cm)
|Crystal class||Dipyramidal (mmm)
H-M symbol: (2/m 2/m 2/m)
|Unit cell||a = 9.621 Å
b = 17.363 Å,
c = 6.994 Å; Z = 4
|Color||Green to yellowish-green and yellow, brown, white and colorless|
|Crystal habit||Spherical, radial aggregates; striated prisms; crusty to stalactitic|
|Cleavage|| perfect,  good,  distinct|
|Fracture||Uneven to subconchoidal|
|Mohs scale hardness||3.5 - 4|
|Luster||Vitreous to resinous, pearly|
|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|
Discovery and occurrence
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.
It occurs in association with crandallite and variscite in fractures in aluminous metamorphic rock, in hydrothermal regions and in phosphate rock deposits. 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.
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