Rhodizite: Structure and Composition

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Science  22 Apr 1966:
Vol. 152, Issue 3721, pp. 500-502
DOI: 10.1126/science.152.3721.500


The mineral rhodizite could not be assigned a chemical formula on the basis of chemical analyses. The solution of the crystal structure reported here reveals that CsB12Be4Al4O28 is the ideal formula. The oxygen atoms occupy all but four sites per cell of cubic close packing whose period is ½a. The boron, beryllium, and aluminum atoms occupy interstices of this array, the first two in tetrahedral coordination, the last in octahedral coordination. Together these atoms form a continuous network whose composition is B12Be4Al4O28, which should be neutral. The alkali atom is enclosed in a cage in this network and presumably is not behaving as an ion.