Uneven, Uneven, Gemstones of the world (2001) More from other references
ConchoidalWalter Schumann, Gemstones of the world (2001), ConchoidalWalter Schumann, Gemstones of the world (2001)
H 4Mg 3Si 2O 9Walter Schumann , Gemstones of the world (2001) More from other references
Al 2Be 3Si 6O 18Martin H.