Conchoidal, ConchoidalArthur Thomas, Gemstones (2009), Brittle
Gems, Sixth Edition (2006), Gems, Sixth Edition (2006)
MgCO 3Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references
SiO 2Michael OâDonoghue , Gems, Sixth Edition (2006)