Conchoidal, ConchoidalArthur Thomas, Gemstones (2009), Brittle
Conchoidal, Conchoidal, Gemstones of the world (2001)
KAlSi 2O 6Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references
SiO 2 · nH 2OWalter Schumann , Gemstones of the world (2001) More from other references