Uneven, Uneven, ConchoidalWalter Schumann, Gemstones of the world (2001) More from other references, Brittle, Conchoidal
ConchoidalArthur Thomas, Gemstones (2009), ConchoidalArthur Thomas, Gemstones (2009), (e.g. graphite).
PbCO 3Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references
PbCrO 4Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references