Tourmaline is actually a group of several different minerals which have similar crystal structures, but complex and variable chemical formulas. Tourmaline is the most varicolored of all gemstones. It occurs in all colors, but red, green, and multicolored are its most famous gem colors.
Color: blue, bluish green, green, greenish blue, green-blue or blue-green, greenish yellow, orangy red, red, red-orange or orange-red, red-purple or purple-red, slightly purplish red, slightly yellowish green, strongly purplish red, strongly yellowish green, very slightly bluish green, yellowish green, yellow-green or green-yellow, colorless, brown, pink
Categories: semi-precious stone
Chemical Composition: (NaCa)(LI,MgFe,Al)9B3Si6(O,OH)31
Crystal Group: Hexagonal
Refractive Index: 1.624(+.005, -.005) – 1.644(+.006, -.006)
Density: 3.06 (.05, +.15)
Occurrence: Brazil, East Africa, Nigeria, Madagascar, U.S.A.