Conchoidal, ConchoidalArthur Thomas, Gemstones (2009), Conchoidal, Brittle, Conchoidal, Brittle
Uneven, Conchoidal, ConchoidalArthur Thomas, Gemstones (2009)
(Na,Ca,K) 8(Si,Al) 12O 24(SO 4,Cl,CO 3) 3(H 2O)Arthur Thomas , Gemstones (2009)
Tourmaline is a series of several different minerals with unique chemical formulas. See The chemical formula of Tourmaline for details.