Uneven, Uneven, ConchoidalAnthony et al, Handbook of mineralogy (2001), Conchoidal, Brittle
Uneven, Conchoidal, ConchoidalArthur Thomas, Gemstones (2009)
Na 8Al 6Si 6O 24(SO 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.