ConchoidalWalter Schumann, Gemstones of the world (2001), ConchoidalWalter Schumann, Gemstones of the world (2001), Brittle, Metallic
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BeAlSiO 4(OH)Michael OâDonoghue , Gems, Sixth Edition (2006) More from other references
Ca(Nd,Ce,La) 2(CO 3) 3F 2Ulrich Henn and Claudio C.