Conchoidal, Conchoidal, Gemstones of the world (2001) More from other references
ConchoidalArthur Thomas, Gemstones (2009), ConchoidalArthur Thomas, Gemstones (2009)
SiO 2 · nH 2OGemdat.org , Management Team (2012)
ZrSiO 4Michael OâDonoghue , Gems, Sixth Edition (2006)