Uneven, torn surfaces, (e.g. fractured metals)., Uneven, Gemstones (2009), torn surfaces, (e.g. fractured metals).
Uneven, Conchoidal, ConchoidalArthur Thomas, Gemstones (2009)
FeO(OH)Arthur Thomas , Gemstones (2009)
Tourmaline is a series of several different minerals with unique chemical formulas. See The chemical formula of Tourmaline for details.