UnevenArthur Thomas, Gemstones (2009), UnevenArthur Thomas, Gemstones (2009)
Conchoidal, ConchoidalAnthony et al, Handbook of mineralogy (2001), Brittle
Ca 2Mg 5Si 8O 22(OH) 2Ulrich Henn and Claudio C.
KNa 2Li(Fe2+ ,Mn2+ ) 2Ti 2Si 8O 24Michael OâDonoghue , Gems, Sixth Edition (2006)