Conchoidal, Conchoidal, Gemstones of the world (2001)
Uneven, Uneven, ConchoidalWalter Schumann, Gemstones of the world (2001)
SiO 2 · nH 2OWalter Schumann , Gemstones of the world (2001) More from other references
Mg 2Al 4Si 5O 18Ulrich Henn and Claudio C.