Conchoidal, Uneven, ConchoidalArthur Thomas, Gemstones (2009), Conchoidal, Brittle
UnevenArthur Thomas, Gemstones (2009), UnevenArthur Thomas, Gemstones (2009), Uneven
Ca 3Al 2(SiO 4) 3Arthur Thomas , Gemstones (2009)
FeS 2Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references