Conchoidal, ConchoidalAnthony et al, Handbook of mineralogy (2001), Brittle
Micaceous, Brittle
KNa 2Li(Fe2+ ,Mn2+ ) 2Ti 2Si 8O 24Michael OâDonoghue , Gems, Sixth Edition (2006)
KAl 2AlSi 3O 10(OH) 2Walter Schumann , Gemstones of the world (2001) More from other references