Conchoidal, Brittle, Conchoidal, Brittle, Conchoidal, ConchoidalArthur Thomas, Gemstones (2009), Brittle, Conchoidal
Gemstones (2009), UnevenArthur Thomas, Gemstones (2009)
PbSO 4Michael OâDonoghue , Gems, Sixth edition (2006) More from other references
Al 2SiO 5Arthur Thomas , Gemstones (2009)