Gems, Sixth Edition (2006), Gems, Sixth Edition (2006)
Conchoidal, ConchoidalArthur Thomas, Gemstones (2009), Brittle
SiO 2Michael OâDonoghue , Gems, Sixth Edition (2006)
KAlSi 2O 6Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references