Frost Ray L, López Andrés, Scholz Ricardo, Lima Rosa Malena Fernandes
School of Chemistry, Physics and Mechanical Engineering, Science and Engineering Faculty, Queensland University of Technology, GPO Box 2434, Brisbane, Queensland 4001, Australia.
School of Chemistry, Physics and Mechanical Engineering, Science and Engineering Faculty, Queensland University of Technology, GPO Box 2434, Brisbane, Queensland 4001, Australia.
Spectrochim Acta A Mol Biomol Spectrosc. 2015 Feb 25;137:827-31. doi: 10.1016/j.saa.2014.09.017. Epub 2014 Sep 22.
We have studied the mineral poldervaartite CaCa[SiO3(OH)(OH)] which forms a series with its manganese analogue olmiite CaMnSiO3(OH) using a range of techniques including scanning electron microscopy, thermogravimetric analysis, Raman and infrared spectroscopy. Chemical analysis shows the mineral is reasonably pure and contains only calcium and manganese with low amounts of Al and F. Thermogravimetric analysis proves the mineral decomposes at 485°C with a mass loss of 7.6% compared with the theoretical mass loss of 7.7%. A strong Raman band at 852 cm(-1) is assigned to the SiO stretching vibration of the SiO3(OH) units. Two Raman bands at 914 and 953 cm(-1) are attributed to the antisymmetric vibrations. Intense prominent peaks observed at 3487, 3502, 3509, 3521 and 3547 cm(-1) are assigned to the OH stretching vibration of the SiO3(OH) units. The observation of multiple OH bands supports the concept of the non-equivalence of the OH units. Vibrational spectroscopy enables a detailed assessment of the molecular structure of poldervaartite.
