Kyanite (Cyprine)

Big Photo

Nepal
3.03 carats
© Mineral Classics

Kyanite is named after Greek word for "blue", because of its colour. Some fine specimens have sapphire-blue colour with violet pleochroism.

Kyanite has a wide variations of hardness in the same crystal depending on direction (across or along axes). It complicates the cutting of this material.

Cut stones reach 10 - 15 carats. Varieties with alexandrite effect and cat's eye are known.

Kyanite Gemstones by Colour

This table shows the variety of hues this gemstone can be found in. Click on a photo for more information.
 
 
 
 

Kyanite Gemstones by Size

This table shows distribution of Kyanite gemstone sizes that are listed on this site. This can give a good indication as to the general availability of this gemstone in different sizes.
Contributed photos
Lightest:0.34 cts
Heaviest:9.48 cts
Average:2.40 cts
Total photos:52
Do you have a larger Kyanite? Why not upload a photo?
0.34ct to 1.25ct1.25ct to 2.17ct2.17ct to 3.08ct3.08ct to 4.00ct4.00ct to 4.91ct4.91ct to 5.82ct5.82ct to 6.74ct6.74ct to 7.65ct7.65ct to 8.57ct8.57ct to 9.48ct
General Information
Other Names/Trade Names:
Chemical Formula
Al
 
2
SiO
 
5
Arthur Thomas, Gemstones (2009)
More from other references
Kyanite Treatments
Pale blue kyanite (also known as cyanite or disthene) is reported to lose its color on heating to 1200°C (Smith et al, 1978) - Nassau (1984)
Physical Properties of Kyanite
Mohs Hardness4 to 7
Walter Schumann, Gemstones of the world (2001) 4 - 4.5 along axes; 6 - 7 across axesMore from other references
Specific Gravity3.55 to 3.70
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
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TenacityBrittle
Walter Schumann, Gemstones of the world (2001)
Cleavage QualityPerfect
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
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FractureSplintery
Arthur Thomas, Gemstones (2009)
Optical Properties of Kyanite
Refractive Index1.710 to 1.735
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
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Optical CharacterBiaxial/+,-
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
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Birefringence0.012 to 0.033
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
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PleochroismBlue stones - strong trichroism: colorless/pale blue - (greenish or violet)-blue - dark blue
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
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Dispersion0.020
Arthur Thomas, Gemstones (2009)
ChatoyancyRare
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
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Colour
Colour (General)Blue, blue-green, green, brown, yellow, red, colourless
Ulrich Henn and Claudio C. Milisenda, Gemmological Tables (2004)
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Causes of ColourBlue, Fe2+-O-Ti4+ charge transfer, Fe2+-O-Fe3+ charge transfer, Fe2+ and Fe3+ in octahedral coordination can all be involved, with contribution from Cr3+ in octahedral coordination. Green, V3+ in octahedral coordination; Fe3+ in octahedral coordination. Orange, Mn3+. Color change, Cr3+ in octahedral coordination
W. William Hanneman, Pragmatic Spectroscopy For Gemologists (2011)
TransparencyTransparent,Translucent
Walter Schumann, Gemstones of the world (2001)
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LustreVitreous,Pearly
Arthur Thomas, Gemstones (2009)
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Fluorescence & other light emissions
Fluorescence (General)Weak; red
Walter Schumann, Gemstones of the world (2001)
Fluorescence (Long-Wave UV)Blue: usually reddish
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
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Crystallography of Kyanite
Crystal SystemTriclinic
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
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HabitOften fibrous
Herve Nicolas Lazzarelli, Blue Chart Gem Identification (2010)
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Geological Environment
Where found:Kyanite occurs in gneisses and schists and in granite pegmatites.
Michael O’Donoghue, Gems, Sixth Edition (2006)
Further Information
Mineral information:Kyanite information at mindat.org
Significant Gem Localities
Kenya
 
  • Taita-Taveta County
Natural History Museum Vienna collection
Madagascar
 
  • Ihorombe
    • Ihosy District
      • Ilakaka
Madagascar - extraLapis English No.1, p. 92
Mozambique
 
Gems, Sixth Edition, Michael O’Donoghue, 2006, p. 422
USA
 
  • Montana
    • Lewis and Clark County
      • East Helena
        • Eldorado Bar
E.Ya. Kievlenko (2003) Geology of gems, p. 70
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