Uneven, Uneven, ConchoidalAnthony et al, Handbook of mineralogy (2001), Conchoidal
ConchoidalArthur Thomas, Gemstones (2009)
Ca(Li 2Al)Al 6(Si 6O 18)(BO 3) 3(OH) 3(OH)Gemdat.org , Management Team (2012)
Tourmaline is a series of several different minerals with unique chemical formulas.