Uneven, Uneven, ConchoidalWalter Schumann, Gemstones of the world (2001)
ConchoidalWalter Schumann, ConchoidalWalter Schumann, Gemstones of the world (2001) More from other references, Brittle, Metallic
Na(Li 1.5Al 1.5)Al 6(Si 6O 18)(BO 3) 3(OH) 3(OH)Gemdat.org , Management Team (2012) Formula given for elbaite.
Be 2BO 3(OH)Ulrich Henn and Claudio C.