Earth Treasures: Kornerupine

By Chisom Ibemere

Kornerupine which is also known as Prismatine is a rare boro-silicate mineral. It crystallizes as brown, green, yellow to colourless in the orthorhombic – dipyramidal crystal system 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.

Kornerupine is found in boron-rich volcanic and sedimentary rocks that have gone through high grade metamorphism. It can also be seen in metamorphosed anorthosite complexes. It is not an attractive gemstone because of its sombre colours. Its colours result from traces of Fe, Cr and V.

Kornerupine has value as a gemstone when it occurs in translucent green to yellow shades. Those that are emerald green in colours are well sought after. It forms a solid solution series with prismatine. It exhibits strong pleochroism, it shows green or reddish brown when viewed from different directions. It has a vitreous lustre.

Kornerupine was first described in 1884 and its name was given in honour of the Danish geologist, Andreas Nikolaus Kornerup Andreas Kornerup (1857–1883). It contains Zircon and Apatite as inclusions.

Kornerupine deposits are found in places like Burma (Myanmar), Canada (Quebec), Kenya, Madagascar, Sri Lanka, Tanzania, and South Africa.