A Raman spectroscopic study of the mineral coquandite Sb6O8(SO4)x(H2O).

Raman spectra of coquandite Sb(6)O(8)(SO(4))x(H(2)O) were studied, and related to the structure of the mineral. Raman bands observed at 970, 990 and 1007 cm(-1) and a series of overlapping bands are observed at 1072, 1100, 1151 and 1217 cm(-1) are assigned to the SO(4)(2-) nu(1) symmetric and nu(3) antisymmetric stretching modes respectively. Raman bands at 629, 638, 690, 751 and 787 cm(-1) are attributed to the SbO stretching vibrations. Raman bands at 600 and 610 cm(-1) and at 429 and 459 cm(-1) are assigned to the SO(4)(2-) nu(4) and nu(2) bending modes. Raman bands at 359 and 375 cm(-1) are assigned to O-Sb-O bending modes. Multiple Raman bands for both SO(4)(2-) and SbO stretching vibrations support the concept of the non-equivalence of these units in the coquandite structure.