Conchoidal, ConchoidalAnthony et al, Handbook of mineralogy (2001), Brittle
Conchoidal, ConchoidalArthur Thomas, Gemstones (2009), Brittle
PbCu(SO 4)(OH) 2Michael OâDonoghue , Gems, Sixth Edition (2006)
Al 6B 5O 15(F,OH) 3Ulrich Henn and Claudio C.