Kornerupine (also called Prismatine) is a rare boro-silicate mineral with the chemical formula (Mg,Fe2+)4(Al,Fe3+)6(SiO4,BO4)5(O,OH)2.

It occurs in boron-rich volcanic and sedimentary rocks which have undergone high grade metamorphism.

[2] Kornerupine is valued as a gemstone when it is found in translucent green to yellow shades.

[4] Strongly pleochroic, it appears green or reddish brown when viewed from different directions.

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