Crystal Tourmaline

Chemical Formula	Tourmaline is a series of several different minerals with unique chemical formulas. See The chemical formula of Tourmaline for details.
Color	White, Colorless, Blue, Red, Green, Yellow, Orange, Brown, Pink, Purple, Gray, Black, Multicolored
Hardness	7 - 7.5
Crystal System	Hexagonal
Refractive Index	1.616 - 1.650
SG	2.9 - 3.3
Transparency	Transparent to opaque
Double Refraction	.018
Luster	Vitreous
Cleavage	3,2
Mineral Class	Tourmaline