ConchoidalWalter Schumann, Gemstones of the world (2001), ConchoidalWalter Schumann, Gemstones of the world (2001)
ConchoidalArthur Thomas, Gemstones (2009), ConchoidalArthur Thomas, Gemstones (2009)
Al 2Be 3Si 6O 18Martin H.
(Ca,Mg,Mn)SiO 3Gemdat.org , Management Team (2012)