Brittle, Metallic, Brittle, Metallic
Uneven, Conchoidal, ConchoidalArthur Thomas, Gemstones (2009)
CaZnSiO 4 · H 2OAnthony et al , Handbook of mineralogy (2001)
Tourmaline is a series of several different minerals with unique chemical formulas. See The chemical formula of Tourmaline for details.