Conchoidal, ConchoidalAnthony et al, Handbook of mineralogy (2001), Brittle
ConchoidalArthur Thomas, Gemstones (2009), ConchoidalArthur Thomas, Gemstones (2009), (e.g. graphite).
SiCArthur Thomas , Gemstones (2009)
PbCrO 4Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references