Uneven, Uneven, ConchoidalAnthony et al, Handbook of mineralogy (2001), Brittle, Conchoidal
Uneven, Conchoidal, ConchoidalArthur Thomas, Gemstones (2009)
3NaAlSi 3O 8 · NaClAnthony 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.