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With colors ranging from brown to beautiful emerald green to shades of yellow, kornerupine is strongly pleochroic. It often contains tiny rutile and graphite inclusions that lend to chatoyancy and asterism. Because of its extreme rarity, kornerupine is almost strictly a collectors stone.

Kornerupine Polished
Kornerupine Classification
Common Name Kornerupine
Species Kornerupine
Kornerupine Optical Properties
Transparency Transparent - Translucent
Dispersion Strength: Moderate Fire Value: 0.019
Refractive Index 1.667-1.680
Birefringence 0.012-0.017
Optic Character Biaxial
Optic Sign Negative
Polariscope Reaction Aggregate (AGG), Doubly Refractive (DR)
Fluorescence SWUV: Inert to strong yellow
LWUV: Inert to strong yellow
Pleochroism Trichroic, strong green, yellow, and red-brown
Kornerupine Characteristic Physical Properties
Hardness 6-7
Streak White
Specific Gravity 3.270-3.350 Typical:3.300
Toughness Varies
Inclusions Kornerupine can contain natural inclusions, zircons and needles. Cat's-eye stones will have parallel rutile or graphite fibers.
Luster Vitreous
Fracture Conchoidal
Cleavage Good, in one direction
Kornerupine Chemistry & Crystallography
Chemical Name magnesium aluminum borosilicate
Chemical Formula Mg3Al6(Si,Al,B)5O21(OH)
Crystal System Orthorhombic
Chemistry Classification Silicate

Kornerupine Colors

  • Brown Kornerupine Brown
  • Yellow Kornerupine Yellow
  • Colorless Kornerupine Colorless
  • White Kornerupine White
  • Blue Kornerupine Blue
  • Green Kornerupine Green
  • Black Kornerupine Black

Kornerupine Spectra

Kornerupine Spectra

Color due to iron. A strongly pleochroic gemstone in which the spectrum is best seen in the greenish beta ray by using a polarizing filter as here, a strong broad band is seen centered at 446nm. in the deep blue accompanied by a weaker one in the green centered at 503nm. In the paler yellowish-brown gamma ray this band at 503nm. is usually all that is seen. Absorption of the dark reddish-brown alpha ray is generally too strong to resolve any of these features.

Jewelry Television acknowledges the significant scientific contributions of John S Harris, FGA to the study of gemstone spectra and with deep appreciation to him, acknowledges the use of his images and related notes about gemstones and their spectra in the educational materials on this website.

Alternate Names


Countries of Origin

Tanzania, United Republic Of; Myanmar; Pakistan; Sri Lanka; Brazil; India

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Tim Matthews


Tim Matthews

Tim Matthews is President and Chief Executive Officer of Jewelry Television® (JTV), as well as a member of the company's Board of Directors. He oversees and leads all aspects of the company's powerful omni-digital retail platform that uniquely specializes in fine jewelry and gemstones. His passion for business and gemstones has led him to become a recognized expert in the field of gemology. He is a life member of the Gemmological Association of Great Britain (Gem-A) and has earned Gem-A's highest degrees, the Gemmology (FGA) and Diamond (DGA) diplomas. He is also a Graduate Gemologist (GG) of the Gemological Institute of America (GIA) and has also completed GIA's Graduate Diplomas in Diamonds, Colored Stones and Pearls. Under his leadership, JTV has become the leader in the sourcing and selling of color gemstones and jewelry.

This page was created on June 27, 2014.

This page was last edited on October 24, 2019.