The molecular structure of the borate mineral szaibelyite MgBO2(OH) – A vibrational spectroscopic study

Abstract

We have studied the borate mineral szaibelyite MgBO2(OH) using electron microscopy and vibrational spectroscopy. EDS spectra show a phase composed of Mg with minor amounts of Fe. Both tetrahedral and trigonal boron units are observed. The nominal resolution of the Raman spectrometer is of the order of 2cm−1 and as such is sufficient enough to identify separate bands for the stretching bands of the two boron isotopes. The Raman band at 1099cm−1 with a shoulder band at 1093cm−1 is assigned to BO stretching vibration. Raman bands at 1144, 1157, 1229, 1318cm−1 are attributed to the BOH in-plane bending modes. Raman bands at 836 and 988cm−1 are attributed to the antisymmetric stretching modes of tetrahedral boron. The infrared bands at 3559 and 3547cm−1 are assigned to hydroxyl stretching vibrations. Broad infrared bands at 3269 and 3398cm−1 are assigned to water stretching vibrations. Infrared bands at 1306, 1352, 1391, 1437cm−1 are assigned to the antisymmetric stretching vibrations of trigonal boron. Vibrational spectroscopy enables aspects of the molecular structure of the borate mineral szaibelyite to be assessed.