ConchoidalArthur Thomas, Gemstones (2009)
Subconchoidal, ConchoidalAnthony et al, Handbook of mineralogy (2001), Brittle, Conchoidal
Tourmaline is a series of several different minerals with unique chemical formulas.
Ca 6Si 2(CO 3) 2(SO 4) 2(OH) 12 · 24H 2OUlrich Henn and Claudio C.