From Wikipedia, the free encyclopedia
Jump to navigation Jump to search
Category Phyllosilicate
(repeating unit)
Strunz classification 9.EA.40
Crystal system Triclinic
Crystal class Pinacoidal (1)
(same H-M symbol)
Space group P1
Unit cell a = 9.69, b = 7.28
c = 22.02 [Å]; α = 92.7°
β = 100.1°, γ = 110.9°; Z = 2
Color White, may show slightly yellow or blue tint
Crystal habit Bladed crystals, typically fibrous, clusters of curved crystals and radial balls
Twinning Lamellar
Cleavage Perfect on {001}
Fracture Splintery
Tenacity Elastic
Mohs scale hardness4 12-5
Luster Vitreous, pearly
Streak White
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 mother zeolites. Okenite is found in India, manila within the state of Maharashtra. Other localities include Bulla Island, Azerbaijan; Aranga, New Zealand; Chile; Ireland and Bordo Island in the Faroe Islands.[2]