Irregular/uneven, UnevenArthur Thomas, Gemstones (2009)
UnevenArthur Thomas, Gemstones (2009), UnevenArthur Thomas, Gemstones (2009)
CaAl 2Si 4O 12 -6H 2OArthur Thomas , Gemstones (2009)
Na 8Al 6Si 6O 24Cl 2Michael OâDonoghue , Gems, Sixth Edition (2006)