Conchoidal, ConchoidalAnthony et al, Handbook of mineralogy (2001), Brittle
Subconchoidal, ConchoidalArthur Thomas, Gemstones (2009), Conchoidal, Brittle
PbCu(SO 4)(OH) 2Michael OâDonoghue , Gems, Sixth Edition (2006)
CaBePO 4(F,OH)Ulrich Henn and Claudio C.