ConchoidalWalter Schumann, Gemstones of the world (2001), ConchoidalWalter Schumann, Gemstones of the world (2001)
Gems, Sixth Edition (2006), Gems, Sixth Edition (2006)
CaTiSiO 5Ulrich Henn and Claudio C.
SiO 2Michael OâDonoghue , Gems, Sixth Edition (2006)