ConchoidalArthur Thomas, Gemstones (2009)
UnevenAnthony et al, Handbook of mineralogy (2001), UnevenAnthony et al, Handbook of mineralogy (2001), Uneven
Tourmaline is a series of several different minerals with unique chemical formulas.
Fe3+ PO 4 · 2H 2OAnthony et al , Handbook of Mineralogy (2001)