Conchoidal, ConchoidalArthur Thomas, Gemstones (2009), Brittle
ConchoidalArthur Thomas, Gemstones (2009), ConchoidalArthur Thomas, Gemstones (2009)
(Zn,Mn2+ )OMichael OâDonoghue , Gems, Sixth Edition (2006)
Be 3Al 2Si 6O 18Ulrich Henn and Claudio C.