Hyalite

Hyalite (Greek - glass stone) is water-clear, glass-like and is generally considered the purest and clearest Opal variety. As a cut gem, it can be confused with glass.
General Information
A variety or type of:Common Opal, which is a variety of Opal
Chemical Formula
SiO
 
2
· nH
 
2
O
Walter Schumann, Gemstones of the world (2001)
Hyalite Simulants
As a cut gem, it can be confused with glass. - Opal, Lithographie, 2007
Physical Properties of Hyalite
Mohs Hardness5.5 to 6.5
Walter Schumann, Gemstones of the world (2001)
TenacityBrittle
Walter Schumann, Gemstones of the world (2001)
Cleavage QualityNone
Walter Schumann, Gemstones of the world (2001)
FractureConchoidal,Splintery
Walter Schumann, Gemstones of the world (2001)
Heat SensitivitySensitive, becomes soft and breaks up
Lithographie, Opal (2007)
Optical Properties of Hyalite
Refractive Index1.37 to 1.52
Walter Schumann, Gemstones of the world (2001)
BirefringenceNone
Walter Schumann, Gemstones of the world (2001)
Colour
Colour (General)Colourless with strong sheen
Walter Schumann, Gemstones of the world (2001)
TransparencyTransparent,Translucent
Walter Schumann, Gemstones of the world (2001)
Fluorescence & other light emissions
Fluorescence (General)Shows brilliant green fluorescence, especially under SW, due to uranium impurities.
Lithographie, Opal (2007)
Crystallography of Hyalite
Crystal SystemAmorphous
Walter Schumann, Gemstones of the world (2001)
HabitUsually takes globular, botryoidal forms
Lithographie, Opal (2007)
Further Information
Mineral information:Hyalite information at mindat.org
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