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Subconchoidal, Uneven, ConchoidalArthur Thomas, Gemstones (2009), Brittle, Conchoidal
Mg 3Si 2O 5(OH) 4Anthony et al , Handbook of mineralogy (2001)
(Mg,Fe2+ ) 9(SiO 4) 4(F,OH)) 2Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references