ConchoidalArthur Thomas, Gemstones (2009), ConchoidalArthur Thomas, Gemstones (2009)
ConchoidalWalter Schumann, ConchoidalWalter Schumann, Gemstones of the world (2001) More from other references, Brittle, Metallic
(Ca,Cr)MgSi 2O 6Gemdat.org , Management Team (2012)
Be 2BO 3(OH)Ulrich Henn and Claudio C.