UnevenWalter Schumann, Gemstones of the world (2001) More from other references, UnevenWalter Schumann, Gemstones of the world (2001) More from other references, Uneven
ConchoidalArthur Thomas, Gemstones (2009), ConchoidalArthur Thomas, Gemstones (2009)
(Zn,Fe)SMichael OâDonoghue , Gems, Sixth Edition (2006) More from other references
Be 3Al 2Si 6O 18Ulrich Henn and Claudio C.