ConchoidalArthur Thomas, Gemstones (2009)
UnevenAnthony et al, Handbook of mineralogy (2001) More from other references, UnevenAnthony et al, Handbook of mineralogy (2001) More from other references, Brittle, Metallic
Tourmaline is a series of several different minerals with unique chemical formulas.
CoAsSAnthony et al , Handbook of mineralogy (2001)