Kornerupine is a rare boro silicate with a long and complicated chemical formula (Mg,Fe2+)4(Al,Fe3+)6(SiO4,BO4)5(O,OH)2. It crystallizes as brown, green, yellow or colorless slender tourmaline like prisms or in massive fibrous forms.

It measures 7 in Moh’s scale of hardness. It occurs in boron-rich volcanic rocks and sedimentary rocks which have undergone high grade metamorphism.

Translucent green to yellow shades of Kornerupine is valued as gemstones. The emerald green varieties are popular favorites.

It was first described in 1884 for an occurrence in Greenland and named in honor of the Danish geologist, Andreas Nikolaus Kornerup.