Conchoidal, ConchoidalArthur Thomas, Gemstones (2009), Brittle
Conchoidal, Brittle, Conchoidal, Brittle, Conchoidal, ConchoidalArthur Thomas, Gemstones (2009), Brittle, Conchoidal
Mg 3Al 2(SiO 4) 3Arthur Thomas , Gemstones (2009)
PbSO 4Michael OâDonoghue , Gems, Sixth edition (2006) More from other references