Conchoidal, ConchoidalAnthony et al, Handbook of mineralogy (2001), Brittle
Irregular/uneven, UnevenArthur Thomas, Gemstones (2009)
KNa 2Li(Fe2+ ,Mn2+ ) 2Ti 2Si 8O 24Michael OâDonoghue , Gems, Sixth Edition (2006)
CaAl 2Si 4O 12 -6H 2OArthur Thomas , Gemstones (2009)