Tourmaline

Tourmaline

(Na,Ca)(Mg,Li,Al,Fe2+)3Al6(BO3)3Si6O18(OH)4

Complex Borosilicate

Hardness: 7-7.5

Cyclosilicate

Trigonal System

Most commonly black, but can range from colorless, brown, violet, yellow, orange, blue, red, green, pink