Tourmaline Explained

Tourmaline is a mineral occurring crystallized in three-sided or six-sided prisms, terminated by three-sided pyramids, the primary form being a rhomboid. It scratches glass easily and is three times as heavy as water. Tourmaline occurs most commonly in igneous and metamorphic rocks, especially in granite, gneiss and mica-slate. Some varieties are transparent, some translucent, some opaque. Some are colorless, and others are green, brown, red, blue or black. Red tourmaline is known as rubellite, blue tourmaline as indicolite, and black tourmaline as schorl. The transparent varieties include various well-known jewelry stones, as the Brazilian sapphire and the Brazilian Emerald. Prisms of tourmaline are much used in polarizing apparatus and the mineral possesses powerful electric properties.