Jet

Jet is an opaque black coalified fossilized drift wood of trees of the family Araucariaceae which is 180 million years old.

Jet is chemically related to brown coal, or lignite, but Jet is more solid and tough.

Jet has been used both as a talisman and a jewel for over four thousand years.

Jet is found in several locations around the world, but only the British and Spanish deposits have been worked commercially.
Photos of natural/un-cut material from mindat.org
Physical Properties of Jet
Mohs Hardness2.5 to 4
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
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Specific Gravity1.19 to 1.35
Walter Schumann, Gemstones of the world (2001)
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Cleavage QualityNone
Walter Schumann, Gemstones of the world (2001)
FractureConchoidal
Walter Schumann, Gemstones of the world (2001)
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Optical Properties of Jet
Refractive Index1.640 to 1.680
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
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Optical CharacterIsotropic
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
BirefringenceNone
Walter Schumann, Gemstones of the world (2001)
PleochroismAbsent
Walter Schumann, Gemstones of the world (2001)
DispersionNone
Walter Schumann, Gemstones of the world (2001)
Colour
Colour (General)Deep black, dark brown
Walter Schumann, Gemstones of the world (2001)
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TransparencyOpaque
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
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LustreWaxy,Dull
Gemdat.org, Management Team (2012) Dull to waxy, but takes an extremely high polish to an almost mirror-finish.More from other references
Fluorescence & other light emissions
Fluorescence (General)None
Walter Schumann, Gemstones of the world (2001)
Crystallography of Jet
Crystal SystemAmorphous
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
Inclusions in Jet
Hot needle: petroleum, coal odor (fossilized wood) - Blue Chart Gem Identification, Herve Nicolas Lazzarelli, 2010, p 4
Further Information
Mineral information:Jet information at mindat.org
Significant Gem Localities
Spain
 
UK
 
  • England
    • North Yorkshire
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