Conchoidal, ConchoidalAnthony et al, Handbook of mineralogy (2001), Brittle
Gemstones (2009), UnevenArthur Thomas, Gemstones (2009)
KNa 2Li(Fe2+ ,Mn2+ ) 2Ti 2Si 8O 24Michael OâDonoghue , Gems, Sixth Edition (2006)
Al 2SiO 5Arthur Thomas , Gemstones (2009)