Conchoidal, Conchoidal, Gemstones of the world (2001) More from other references
UnevenArthur Thomas, Gemstones (2009), UnevenArthur Thomas, Gemstones (2009)
SiO 2 · nH 2OGemdat.org , Management Team (2012)
Na 8Al 6Si 6O 24Cl 2Michael OâDonoghue , Gems, Sixth Edition (2006)