ConchoidalArthur Thomas, Gemstones (2009), ConchoidalArthur Thomas, Gemstones (2009)
Uneven, Uneven, ConchoidalArthur Thomas, Gemstones (2009), Brittle
Be 3Al 2Si 6O 18Ulrich Henn and Claudio C.
Ag 3AsS 3Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references