Conchoidal, Uneven, ConchoidalArthur Thomas, Gemstones (2009), Brittle, Metallic
ConchoidalArthur Thomas, Gemstones (2009)
CaBSiO 4(OH)Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references
Tourmaline is a series of several different minerals with unique chemical formulas.