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UnevenArthur Thomas, Gemstones (2009), UnevenArthur Thomas, Gemstones (2009)
(Mg,Fe2+ ) 5Al(Si 3Al)O 10(OH) 8Anthony et al , Handbook of mineralogy (2001)
Ca 2(Mg,Al) 6(Si,Al,B) 6O 20Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references