Uneven, Uneven, Gemstones of the world (2001) More from other references
ConchoidalWalter Schumann, ConchoidalWalter Schumann, Gemstones of the world (2001) More from other references, Brittle, Metallic
H 4Mg 3Si 2O 9Walter Schumann , Gemstones of the world (2001) More from other references
Be 2BO 3(OH)Ulrich Henn and Claudio C.