Vibrational Spectroscopy of the Multianion Mineral Kemmlitzite (Sr,Ce)Al3(AsO4)(SO4)(OH)6

Some minerals are colloidal and show no X-ray diffraction patterns. Vibrational spectroscopy offers one of the few methods for the assessment of the structure of these types of minerals. Among this group of minerals is kemmlitzite (Sr,Ce)Al-3(AsO4)(SO4)(OH)(6). The objective of this research is to determine the molecular structure of the mineral kemmlitzite using vibrational spectroscopy. Raman microscopy offers a useful method for the analysis of such colloidal minerals. Raman and infrared bands are attributed to the AsO43-, SO42-, and water stretching vibrations. The Raman spectrum is dominated by a very intense sharp band at 984 cm(-1) assigned to the SO42- symmetric stretching mode. Raman bands at 690, 772, and 825 cm(-1) may be assigned to the AsO43- antisymmetric and symmetric stretching modes. Raman bands observed at 432 and 465 cm(-1) are attributable to the doubly degenerate nu(2)(SO4)(2-) bending mode. Vibrational spectroscopy is important in the assessment of the molecular structure of the kemmlitzite, especially when the mineral is nondiffracting or poorly diffracting.