ConchoidalArthur Thomas, Gemstones (2009), ConchoidalArthur Thomas, Gemstones (2009), Brittle, Conchoidal
ConchoidalArthur Thomas, Gemstones (2009), ConchoidalArthur Thomas, Gemstones (2009), Conchoidal, Brittle
ZrO 2Arthur Thomas , Gemstones (2009)
MgAlBO 4Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references