ConchoidalWalter Schumann, Gemstones of the world (2001), ConchoidalWalter Schumann, Gemstones of the world (2001)
ConchoidalArthur Thomas, Gemstones (2009), ConchoidalArthur Thomas, Gemstones (2009), (e.g. graphite).
CaTiSiO 5Ulrich Henn and Claudio C.
PbCrO 4Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references