ConchoidalWalter Schumann, Gemstones of the world (2001), ConchoidalWalter Schumann, Gemstones of the world (2001)
UnevenWalter Schumann, Gemstones of the world (2001) More from other references, UnevenWalter Schumann, Gemstones of the world (2001) More from other references, Uneven
SiO 2Ulrich Henn and Claudio C.
(Zn,Fe)SMichael OâDonoghue , Gems, Sixth Edition (2006) More from other references