Characteristics of Kornerupine:

Chemical Name: Magnesium aluminum borosilicate

Formula: (Mg,Fe²⁺) ₄(Al,Fe³⁺) ₆(SiO ₄,BO ₄) ₅(O,OH) ₂ 

Colors: Green, white, blue

Structure: Orthorhombic

Hardness: 6.5-7

Specific Gravity: 3.3-3.5

Refractive Index: 1.66-1.69

Lustre: Vitreous

Streak: White

Locations: Madagascar, Sri Lanka, Canada, Greenland, Norway, Russia

What is Kornerupine? 

Kornerupine is a rare borosilicate mineral, named in honor of Danish geologist, Andreas Nicolaus Kornerup. Its crystals can resemble tourmaline prisms, and are found in shades of brown, green, and yellow all the way through to colorless; of all these, emerald-green and blue are the most highly valued. It is still relatively rare in faceted stones. When faceting, the lapidary must orient the stone carefully in order to obtain the best color, with the table facet parallel to the prism faces of the crystal.