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