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