Conchoidal, ConchoidalArthur Thomas, Gemstones (2009), Brittle
Irregular/uneven, UnevenArthur Thomas, Gemstones (2009)
Pb 5(AsO 4) 3ClMichael OâDonoghue , Gems, Sixth Edition (2006) More from other references
CaAl 2Si 4O 12 -6H 2OArthur Thomas , Gemstones (2009)