-40%
Round Cut~Natural~Kornerupine/Prismatine~0.5TCW~Balochistan, Pak~US Ship
$ 8.97
- Description
- Size Guide
Description
Round cut loose gemstone, 0.5TCW kornerupine/prismatine, green colorKornerupine (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 orthohombic - 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.
It occurs in boron-rich volcanic and sedimentary rocks which have undergone high grade metamorphism. It is also found in metamorphosed anorthosite complexes.
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. Strongly pleochroic, it appears green or reddish brown when viewed from different directions. It has a vitreous luster.