Uneven, Uneven, ConchoidalWalter Schumann, Gemstones of the world (2001) More from other references, Brittle, Conchoidal
Gems, Sixth Edition (2006), Gems, Sixth Edition (2006)
PbCO 3Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references
SiO 2Michael OâDonoghue , Gems, Sixth Edition (2006)