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
SiO 2(+Al 2O 3)Walter Schumann , Gemstones of the world (2001)
H 4Mg 3Si 2O 9Walter Schumann , Gemstones of the world (2001) More from other references