A variety of tourmaline much sought after on account of its beauty and rarity. Its color ranges from a deep, radiant green-blue to blue. It is also known as an indigolith.
Formula: Na(Li, Al)3Al6B3Si6O27(OH)3(OH,F)
Hardness: 7 – 7.5
Density: 2.90 – 3.40 g/cm3
Refractive Index: 1.614 – 1.666 DR: 0.014 – 0.032
Color:
Blue, greenish-blue, greyish-blue
Countries of Origin:
Brazil, Namibia, Mozambique
Birthstone: October