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Subconchoidal, Conchoidal, Brittle, ConchoidalArthur Thomas, Gemstones (2009)
(Mg,Fe2+ ) 5Al(Si 3Al)O 10(OH) 8Anthony et al , Handbook of mineralogy (2001)
TiO 2Michael OâDonoghue , Gems, Sixth edition (2006) More from other references