Uneven, Uneven, ConchoidalArthur Thomas, Gemstones (2009), Brittle, Metallic
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KCa 2AlBe 2Si 12O 30 · 0.5H 2OMichael OâDonoghue , Gems, Sixth Edition (2006) More from other references
Na 2(Ti,Fe)Si 4(O,F) 11Ulrich Henn and Claudio C.