Uneven, Uneven, Gems, Sixth Edition (2006)
Conchoidal, ConchoidalArthur Thomas, Gemstones (2009), Brittle
Al 2O 3Michael OâDonoghue , Gems, Sixth Edition (2006)
Pb 5(AsO 4) 3ClMichael OâDonoghue , Gems, Sixth Edition (2006) More from other references