ConchoidalArthur Thomas, Gemstones (2009), ConchoidalArthur Thomas, Gemstones (2009)
Uneven, Uneven, Gems, Sixth Edition (2006)
CaZrBAl 9O 18Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references
Al 2O 3Michael OâDonoghue , Gems, Sixth Edition (2006)