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