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