Okenite

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Okenite
Okenite and Gyrolite.jpg
Okenite
General
Category Phyllosilicate
Formula
(repeating unit)
CaSi2O5·2H2O
Strunz classification 09.EA.40
Crystal symmetry Triclinic Space group: P1 or P1
Unit cell a = 9.69 Å, b = 7.28 Å, c = 22.02 Å; α = 92.7°, β = 100.1°, γ = 110.9°; Z=2
Identification
Color White, may show slightly yellow or blue tint
Crystal habit Bladed crystals, typically fibrous, clusters of curved crystals and radial balls
Crystal system Triclinic
Twinning Lamellar
Cleavage Perfect on {001}
Tenacity Elastic
Mohs scale hardness 4½-5
Luster Vitreous, pearly
Diaphaneity Transparent, translucent
Specific gravity 2.28 - 2.33
Optical properties Biaxial (-)
Refractive index nα = 1.512 - 1.532 nβ = 1.514 - 1.535 nγ = 1.515 - 1.542
Birefringence δ = 0.003 - 0.010
2V angle Measured: 60°
References [1][2][3]

Okenite (CaSi2O5·2H2O)[2] is a silicate mineral that is usually associated with zeolites. It most commonly is found as small white "cotton ball" formations within basalt geodes. These formations are clusters of straight, radiating, fibrous crystals that are both bendable and fragile.[4]

Discovery and occurrence[edit]

It was first described in 1828 for an occurrence at Disko Island, Greenland and named for German naturalist Lorenz Oken (1779–1851).[3]

Minerals associated with okenite include apophyllite, gyrolite, prehnite, chalcedony, goosecreekite and many of the other zeolites. Okenite is found in India, mainly within the state of Maharashtra. Other localities include Bulla Island, Azerbaijan; Aranga, New Zealand; Chile; Ireland and Bordo Island in the Faroe Islands.[2]

References[edit]