ConchoidalWalter Schumann, ConchoidalWalter Schumann, Gemstones of the world (2001) More from other references, Brittle, Metallic
Conchoidal, Uneven, ConchoidalArthur Thomas, Gemstones (2009)
Be 2BO 3(OH)Ulrich Henn and Claudio C.
(Mg,Fe2+ )Al 2O 4Gemdat.org , Management Team (2012) More from other references