Tourmaline is a popular gem with a rich variety of colours including red, orange, pink, yellow, green, blue, purple, black, brown and Colourless (white) tones. Bi coloured with 2 distinct colours are popular, but rare in clean gems. The most expensive is the Paraiba, a Stunning bright icy blue colour, with quality stones very rare and expensive.
One of my favourite pretties, with amazing sparkle when not commercially cut and clean. With larger stone 2ct or more allowing for stunning statement designs. 4ct or larger gems are rare as prices reflect rarity in the clean gems, with supply erratic.
Tourmaline is doubly refractive with an RI of 1.619-1.650 and a specific gravity of 3.00-3.20.