Conchoidal, 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
SiO2
(Zn,Fe)SMichael OâDonoghue , Gems, Sixth Edition (2006) More from other references