kornerupine

{{Infobox mineral | name = Kornerupine | boxwidth = | image = Kornerupine-162065.jpg | alt = | caption = | category = Borosilicates | formula = | IMAsymbol = Krn | molweight = | strunz = 9.BJ.50 (10 ed) VIII/B.31-10 (8 ed) | dana = 58.01.01.01 | system = Orthorhombic | class = Dipyramidal (mmm) H-M symbol: (2/m 2/m 2/m) | symmetry = Cmcm | unit cell = a = 15.99, b = 13.7, c = 6.7 [Å]; Z = 4 | color = Colorless, white, grey, greenish, bluish, brown, black | habit = Prismatic crystals, radiating, massive, fibrous | twinning = | cleavage = Good on {110} | fracture = | tenacity = | mohs = 6 to 7 | luster = Vitreous | streak = White | diaphaneity = Transparent to translucent and opaque | gravity = 3.29–3.35 | density = | polish = | opticalprop = Biaxial (−) | refractive = nα = 1.660 – 1.671 nβ = 1.673 – 1.683 nγ = 1.674 – 1.684 | birefringence = δ = 0.014 | pleochroism = X = colorless to green; Y = colorless, pale brownish yellow, pale yellowish green; Z = pale brownish green, green, light amber | 2V = Measured: 3° to 48° | dispersion = | extinction = | length fast/slow = | fluorescence = | absorption = | melt = | fusibility = | diagnostic = | solubility = | impurities = | alteration = | other = | prop1 = | prop1text = | references = }}

Kornerupine (also called Prismatine) is a rare boro-silicate mineral with the chemical formula . 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 nα=1.660 – 1.671, nβ=1.673 – 1.683 and nγ=1.674 – 1.684.