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ConchoidalWalter Schumann, Gemstones of the world (2001), ConchoidalWalter Schumann, Gemstones of the world (2001)
Ca 2(Mg,Fe,Mn,Al) 2(SiO 4)(Si 2O 7)(OH) 2 · H 2OUlrich Henn and Claudio C.
SiO 2Walter Schumann , Gemstones of the world (2001)