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
Photos of natural/un-cut material from mindat.org
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)
More from other references
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)
More from other references
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
 
  • Fianarantsoa Province
    • Ihorombe Region
      • Ihosy District
        • Ilakaka Commune
Madagascar - extraLapis English No.1, p. 92
Mozambique
 
Gems, Sixth Edition, Michael O’Donoghue, 2006, p. 422
USA
 
  • Montana
    • Lewis and Clark Co.
      • East Helena
        • Eldorado Bar
E.Ya. Kievlenko (2003) Geology of gems, p. 70
Copyright © Jolyon & Katya Ralph 1993-2018. Site Map. Locality, gem & photograph data are the copyright of the individuals who submitted them. For more information please contact the . Gemdat.org is an online information resource dedicated to providing free gemmological information to all.