Conchoidal, Brittle, Conchoidal, UnevenArthur Thomas, Gemstones (2009), Brittle, Conchoidal
Gems, Sixth Edition (2006), Gems, Sixth Edition (2006)
CaSO 4Michael OâDonoghue , Gems, Sixth edition (2006) More from other references
SiO 2Michael OâDonoghue , Gems, Sixth Edition (2006)