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(repeating unit)
Strunz classification9.BJ.50 (10 ed)
VIII/B.31-10 (8 ed)
Dana classification58.01.01.01
Crystal systemOrthorhombic
Crystal classDipyramidal (mmm)
H-M symbol: (2/m 2/m 2/m)
Space groupCmcm
Unit cella = 15.99, b = 13.7, c = 6.7 [Å]; Z = 4
ColorColorless, white, grey, greenish, bluish, brown, black
Crystal habitPrismatic crystals, radiating, massive, fibrous
CleavageGood on {110}
Mohs scale hardness6 to 7
DiaphaneityTransparent to translucent and opaque
Specific gravity3.29 - 3.35
Optical propertiesBiaxial (-)
Refractive indexn? = 1.660 - 1.671 n? = 1.673 - 1.683 n? = 1.674 - 1.684
Birefringence? = 0.014
PleochroismX = colorless to green; Y = colorless, pale brownish yellow, pale yellowish green; Z = pale brownish green, green, light amber
2V angleMeasured: 3° to 48°

Kornerupine (also called Prismatine) is a rare boro-silicate mineral with the formula (Mg,Fe2+)4(Al,Fe3+)6(SiO4,BO4)5(O,OH)2. It crystallizes in the orthorhombic - dipyramidal crystal system as brown, green, yellow to colorless slender tourmaline like prisms or in massive fibrous forms. It has a Mohs hardness of 7 and a specific gravity of 3.3 to 3.34. Its indices of refraction are n?=1.660 - 1.671, n?=1.673 - 1.683 and n?=1.674 - 1.684.

It occurs in boron-rich volcanic and sedimentary rocks which have undergone high grade metamorphism. It is also found in metamorphosed anorthosite complexes.[1]

Kornerupine is valued as a gemstone when it is found in translucent green to yellow shades. The emerald green varieties are especially sought after. It forms a solid solution series with prismatine.[3] Strongly pleochroic, it appears green or reddish brown when viewed from different directions. It has a vitreous luster.

It was first described in 1884 for an occurrence in Fiskernæs in southwest Greenland. It was named in honor of the Danish geologist, Andreas Nikolaus Kornerup (1857-1883).[2] Although kornerupine was named in 1884, it was not until 1912 that gem-quality material was found and it remains uncommon to this day.

Deposits are found in Burma (Myanmar), Canada (Quebec), Kenya, Madagascar, Sri Lanka, Tanzania, and South Africa.


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