Gyrolite

Gyrolite

Gyrolite
General
Category Phyllosilicate
Formula
(repeating unit)
NaCa16Si23AlO6(OH)8·14H2O
Strunz classification 09.EE.30
Dana classification 73.2.2c.1
Crystal system Triclinic
Unit cell a = 9.74 Å, b = 9.74 Å, c = 22.4 Å; α = 95.71°, β = 91.51°, γ = 120.01°; Z=4
Identification
Color White, colorless, green, yellow or brown
Crystal habit Compact, lamellar, platy
Crystal symmetry Triclinic space group: P1
Twinning Lamellar
Cleavage Perfect on {001}
Tenacity Brittle
Mohs scale hardness
Luster Vitreous, pearly
Diaphaneity Transparent, translucent, opaque
Density 2.45 - 2.51
Optical properties Biaxial (-)
Refractive index nα = 1.535 nβ = 1.548 nγ = 1.549
Birefringence δ = 0.0140
References [1][2][3]

Gyrolite (NaCa16Si23AlO6(OH)8·14H2O)[2] is a silicate mineral that is usually associated with zeolites. It most commonly is found as spherical or radial formations in hydrothermally altered basalt and basaltic tuffs.[2] These formations can be glassy, dull or fibrous in appearance.[4]

Gyrolite is also known as Centrallasite, Glimmer Zeolite or Gurolite.[2]

Discovery and occurrence

It was first described in 1851 for an occurrence at The Storr on the isle of Skye, Scotland and is named from the Greek word for circle, guros, based on the round form in which it is commonly found.[3]

Minerals associated with gyrolite include apophyllite, okenite and many of the mother zeolites.[4] Gyrolite is found in Scotland, Ireland; Italy, Faroe Islands, Greenland, India, Japan, USA, Canada and various other localities.[1][2]

References

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