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