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Conchoidal, UnevenArthur Thomas, Gemstones (2009), Brittle
(Mg,Fe)Al 3(BO 4)(SiO 4)OUlrich Henn and Claudio C.
Zn 2(AsO 4)(OH) · H 2OMichael OâDonoghue , Gems, Sixth Edition (2006) More from other references