UnevenWalter Schumann, Gemstones of the world (2001) More from other references, UnevenWalter Schumann, Gemstones of the world (2001) More from other references, Uneven
ConchoidalMichael OâDonoghue, Gems, Sixth Edition (2006), Gems, Sixth Edition (2006)
(Zn,Fe)SMichael OâDonoghue , Gems, Sixth Edition (2006) More from other references
SiO2