UnevenArthur Thomas, Gemstones (2009), UnevenArthur Thomas, Gemstones (2009), Conchoidal, Brittle
Conchoidal, Conchoidal, Gemstones of the world (2001) More from other references
BaCO 3Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references
SiO 2 · nH 2OGemdat.org , Management Team (2012)