Conchoidal, ConchoidalArthur Thomas, Gemstones (2009), ConchoidalArthur Thomas, Gemstones (2009), Brittle, Conchoidal
Gems, Sixth Edition (2006), Gems, Sixth Edition (2006)
CaCO 3Ulrich Henn and Claudio C.
SiO 2Michael OâDonoghue , Gems, Sixth Edition (2006)