Kornerupine
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Kornerupine
Kornerupine
Kornerupine-162065.jpg
General
CategoryBorosilicates
Formula
(repeating unit)
(Mg,Fe2+)4(Al,Fe3+)6(SiO4,BO4)5(O,OH)2
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
Identification
ColorColorless, white, grey, greenish, bluish, brown, black
Crystal habitPrismatic crystals, radiating, massive, fibrous
CleavageGood on {110}
Mohs scale hardness6 to 7
LusterVitreous
StreakWhite
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°
References[1][2][3]

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.

References


  This article uses material from the Wikipedia page available here. It is released under the Creative Commons Attribution-Share-Alike License 3.0.

Kornerupine
 



 



 
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