Uneven, Conchoidal, ConchoidalArthur Thomas, Gemstones (2009)
ConchoidalArthur Thomas, Conchoidal, Brittle
Tourmaline is a series of several different minerals with unique chemical formulas. See The chemical formula of Tourmaline for details.
Mn 3Al 2(SiO 4) 3Arthur Thomas , Gemstones (2009)