Conchoidal, Conchoidal, Gemstones of the world (2001)
ConchoidalArthur Thomas, Gemstones (2009), ConchoidalArthur Thomas, Gemstones (2009)
SiO 2 · nH 2OWalter Schumann , Gemstones of the world (2001)
CaZrBAl 9O 18Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references