Kornerupine Value, Price, and Jewelry Information

KORNERUPINE: Kenya (0.55), Madagascar (1.23), Kenya (1.47). Photo © Joel E. Arem, PhD, FGA. Used with permission.

Kornerupine

Star kornerupine also has been found (Mogok, Myanmar) but is very rare. Kornerupine is generally dark brown or green and not very attractive due to the somber colors. The light green material from Kenya is much more appealing, but the sizes are always small (under 3 carats as a rule). The color is caused by traces of Fe, Cr. and V. Despite the fact that many stones are in museums and private collections, kornerupine is a rather rare gemstone and, for the collector, worth acquiring when available.

Kornerupine Information

Data Value
Name Kornerupine
Stone Sizes Most gems are under 5 carats, but occasional large material from Sri Lanka, Burma, or East Africa yields a gem in the 25-30 carat range. Canadian crystals are large (up to 2 inches across) but are not generally cuttable. The largest crystals of all, from Greenland, yield only small cut stones. Smithsonian Institution (Washington, D.C): 21.6 (brown, Sri Lanka); 10.8 (brown, Madagascar); 8.1 (green, Sri Lanka). Devonian Group (Calgary, Alberta, Canada): 6.4 (Sri Lanka). Private Collection: 16.50 (golden, Sri Lanka); 7.57 (catseye, Sri Lanka).
Formula Mg3AI6(Si,Al,B)5O21(OH).
Colors Colorless, white, pink, greenish yellow, blue-green, sea green, dark green, brown, black.
Fracture Conchoidal
Hardness 6-7
Cleavage Perfect 2 directions
Crystallography Orthorhombic; crystals prismatic; also fibrous, columnar.
Refractive Index Varies by locality, 1.661-1.699. See "Identifying Characteristics" below.
Birefringence 0.013-0.017
Dispersion 0.018
Luminescence None (Sri Lanka) or yellowish (Burmese green gems, stronger in East African stones) in LW and SW.
Luminescence Present Yes
Luminescence Type Fluorescent, UV-Long, UV-Short
Absorption Spectrum Weak band seen at 5030.
Pleochroism Pronounced and visible to the naked eye: Sri Lanka; Madagascar: yellowish brown/brown/greenish. Kwale Distnct, Kenya: intense green/light green/greenish yellow. Kenya; Tanzania: emerald green/bluish gray/reddish purple. Greenland: dark green/reddish blue/light blue.
Optics Varies by locality. Biaxial (-), 2V= 3-48°. Gems sometimes pseudo-uniaxial. See "Identifying Characteristics" below.
Optic Sign Biaxial -
Luster Vitreous.
Specific Gravity 3.27-3.45; gems are 3.28-3.35.
Transparency Transparent to opaque.
Phenomena Chatoyancy, asterism (very rare).

Optics: varies with locality:

Locality

a

β

γ

Birefringence

Density

Madagascar

1.661

1.673

1.674

0.013

3.28

Sri Lanka

1.669

1.681

1.682

0.013

3.35

catseye

1.673

1.686

1.690

0.017

Germany

1.675

1.687

1.687

0.014

3.37

Natal

1.682

1.696

1.699

0.017

3.45

Greenland

1.667

1.679

1.682

0.015

3.30

East Africa

1.662

1.675

1.677

0.015

Biaxial (-), 2V= 3-48°; gems sometimes pseudo-uniaxial.

Inclusions: Zircon, apatite crystals.

Occurrence: First found in Greenland in radiating crystals (not gemmy), later in cuttable fragments.

Finskenaesset, Southwest Greenland: giant crystals up to 23 cm, yielding cabochons and small (up to  2 carats) faceted gems of dark green color.

Weligama gem gravels, Matara district,  SriLanka: greenish to dark yellowish-green catseyes. The eye effect is intense. Stones tend to be small, but cabochons over 7 carats have been reported. Also from Matale, yellowbrown and reddish pebbles, in gravels.

Mogok, Burma: greenish-brown material in gem gravels.

Kwale district, Kenya: light green material, some large clean pieces; colored green by vanadium. Tanzania: chrome variety with green color, cuttable.

Gatineau County, Quebec, Canada: large crystals, dark green to greenish yellow.

Itrongahy, Madagascar: large gemmy dark green crystals, also pale aquamarine-blue.

Betroka and Inanakafy, Madagascar: gray to brown prismatic crystals.

Comments: Star kornerupine also has been found I(Mogok, Burma) but is very rare. Kornerupine is generally dark brown or green and not very attractive due to the somber colors. The light green material from Kenya is much more appealing, but the sizes are always small (under 3 carats as a rule). The color is caused by traces of Fe, Cr. and V. Despite the fact that many stones are in museums and private collections, kornerupine is a rather rare gemstone and, for the collector, worth acquiring when available.

Name: After the Danish geologist Kornerup.