Variations in infrared spectra of carbonate minerals are indicative of changes in symmetry of the ionic carbonate molecule. The point-group symmetry of the ion determined from spectral considerations is generally compatible with its site symmetry. Molecular symmetry does not, however, vary systematically with crystal class. The existence of more than one non-equivalent molecule per unit cell is reflected in certain carbonates by spectral enrichment in the wavelength region of one or more of the fundamental c1 egenerate or nondegenerate vibrations. Alternative causes of spectral multiplicity are also considered; however, the enrichment has been observed only for minerals which are known or suspected from x-ray data to contain non-equivalent carbonate ions.

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