Tourmaline: mineral with the chemical composition (Na,K,Ca)(Li,Mg,Fe,Al,Ti,Mn)3(Al,Cr,Fe,V)6(BO3)3(Si6O18)(OH,O)3(F,O,OH). It ranges from transparent to opaque, with a vitreous luster and colors spanning from colorless to all other hues. It crystallizes in the Trigonal System and appears as striated, elongated crystals as well as prismatic crystals. Based on chemical composition and color, there are numerous varieties of Tourmaline, including Acroite (colorless), Dravite (yellow-brown, brown), Indicolite (various shades of blue), Rubellite (pink and red), Schorl (black), and Verdelite (various shades of green).
