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