Kornerupine is a rare borosilicate mineral and gemstone. Its intense color resembles that of an 
emerald. It also shares the same inclusions as emerald. Kornerupine is mostly a collectors' stone. The stone was named for the outstanding Danish mineralogist Andreas Kornerup (1857-81), who explored Greenland where the mineral was first discovered at Fiskenaesset in 1884. Gem quality material however, was not found until around 1912.
Kornerupine is a metamorphic mineral. It's a complex magnesium aluminum boro-silicate whose crystals have long prismatic forms or occur as rounded grains often found in gravel deposits behind rocks and at bends of rivers. Kornerupine is found in association with other gems like 
sapphire, chrysoberyl, 
ruby, 
topaz, 
garnet, zircon, diopside, andalusite, spinel, sphene, and iolite. Kornerupine is a brittle, vitreous, and transparent stone, rating a 6.5-7 on the hardness scale.
Kornerupine is distinguished by its pleochroic colors that change from yellowish green, through blue, to brownish red, as the stone is turned. The best color is seen through the side of the crystal, so gem quality kornerupine is cut with the length of the crystal parallel to the table facet. Kornerupine occurs in all the shades of green, from yellow-green, green-yellow, and yellow brown, to brown. It has been known to be confused with tourmaline and enstatite.
Kornerupine is one of the more familiar, rare gemstones in Sri Lanka. Aside from Sri Lanka, Kornerupine can be found all over the world. Fiskenaesset, Nuuk, in Greenland, is the type locality of kornerupine, but specimens there are rare and are not of gem quality. The best gemstones, including rare cats-eye forms, are found in Mogok, Mandalay, in central Burma (Myanmar). Some of the finest colors of kornerupine gems are mined at Betroka, Madagasautomobile. Other sources include Ratnapura in Southwest Sri Lanka, various locations in Brazil, and the Harts range in Northern territory, Australia. African localities of the green gem quality material include Kenya and Tanzania.
