ConchoidalWalter Schumann, Gemstones of the world (2001), ConchoidalWalter Schumann, Gemstones of the world (2001)
UnevenArthur Thomas, Gemstones (2009), UnevenArthur Thomas, Gemstones (2009), Conchoidal, Brittle
SiO 2Walter Schumann , Gemstones of the world (2001)
BaCO 3Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references