Uneven, Conchoidal, ConchoidalArthur Thomas, Gemstones (2009)
ConchoidalGemdat.org, Management Team (2012), ConchoidalGemdat.org, Management Team (2012)
Tourmaline is a series of several different minerals with unique chemical formulas. See The chemical formula of Tourmaline for details.
(Cu) 3(OH) 2(CO 3) 2 + Cu 2(CO 3)(OH) 2Gemdat.org , Management Team (2012)