Uneven, Uneven, ConchoidalArthur Thomas, Gemstones (2009)
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Na 4AlBeSi 4O 12ClMichael OâDonoghue , Gems, Sixth Edition (2006) More from other references
(Mg,Fe2+ ) 3Si 2O 5(OH) 4Anthony et al , Handbook of mineralogy (2001)