SAPPHIRINE

    Class : Silicates
    Subclass : Inosilicates
    Crystal system : Monoclinic
    Chemistry : Mg7Al18Si3O40
    Rarity : Rare to uncommon

Sapphirine is a rare mineral resulting from intense metamorphism, at the limit of the granulite and amphibolite facies, of aluminous and magnesian rocks poor in silica. Its light blue to blue-black color and vitreous luster are reminiscent of sapphire, hence its name. It most often occurs in microscopic grains, very rarely in flattened crystals up to 5 cm with a pseudohexagonal outline. It is occasionally used as a gemstone.

Main photo : Sapphirine from Morafeno, Tranomaro, Anosy, Madagascar © Rob Lavinsky

Sapphirine in the World

Sapphirine is known from about thirty sites in the world but few have yielded aesthetic samples. Magnificent blue crystals, often gemmy, probably the most beautiful in the world, have been extracted from Malagasy anorthosites (Androy, Betroka, Bekily...). South Africa, with the deposits of the Postmaburg and Messina regions, also contains superb blue crystals that rival the Malagasy crystals. Original pale yellow sapphirine crystals come from Mautia (Tanzania).

Sapphirine in France

In France, sapphirine is known in Salzuit (Haute-Loire) in the leptyno-amphibolic complex of Haut-Allier, associated with corundum. It is also reported in the granulites of the Etang de Lers (Ariège).

Right photo : Sapphirine from the Etang de Lers, Ariège, France © François Périnet

Twinning

No twinning known for this mineral species.

Fakes and treatments

No fakes listed for this mineral species.


Hardness : 7.5
Density : 3.4 to 3.5
Fracture : Irregular to sub-conchoidal
Streak : White

TP : Translucent to transparent
RI : 1.701 to 1.734
Birefringence : 0.004 to 0.005
Optical character : Biaxial -
Pleochroism : Visible
Fluorescence : None

Solubility : Insoluble

Magnetism : NoneRadioactivity : None