Gemstones (2009), UnevenArthur Thomas, Gemstones (2009), Brittle, Metallic
Irregular/uneven, UnevenArthur Thomas, Gemstones (2009)
CuSMichael OâDonoghue , Gems, Sixth edition (2006) More from other references
CaAl 2Si 4O 12 -6H 2OArthur Thomas , Gemstones (2009)