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ConchoidalArthur Thomas, Gemstones (2009), ConchoidalArthur Thomas, Gemstones (2009), Uneven
Ca 2(Mg,Fe,Mn,Al) 2(SiO 4)(Si 2O 7)(OH) 2 · H 2OUlrich Henn and Claudio C.
(Mn2+ ,Fe2+ ,Mg,Ca) 2(PO 4)(F,OH)Michael OâDonoghue , Gems, Sixth Edition (2006)