Uneven, Uneven, ConchoidalAnthony et al, Handbook of mineralogy (2001)
Uneven, Conchoidal, ConchoidalArthur Thomas, Gemstones (2009)
(Zn,Mn2+ ,Fe2+ )(Fe3+ ,Mn3+ ) 2O 4Anthony 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.