The spectroscopic characterization of the sulphate mineral ettringite from Kuruman manganese deposits, South Africa.

• Autor(a) principal: Frost, Ray Leslie
• Data de Publicação: 2013
• Outros Autores: López, Andrés, Xi, Yunfei, Cipriano, Ricardo Augusto Scholz, Costa, Geraldo Magela da, Lima, Rosa Malena Fernandes, Granja, Amanda
• Tipo de documento: Artigo
• Idioma: eng
• Título da fonte: Repositório Institucional da UFOP
• Texto Completo: http://www.repositorio.ufop.br/handle/123456789/4154; https://doi.org/10.1016/j.vibspec.2013.08.011
• topic: Raman spectroscopy; Ettringite; Kuruman; Infrared spectroscopy; Thermal analysis

The mineral ettringite has been studied using a number of techniques, including XRD, SEM with EDX, thermogravimetry and vibrational spectroscopy. The mineral proved to be composed of 53% of ettringite and 47% of thaumasite in a solid solution. Thermogravimetry shows a mass loss of 46.2% up to 1000 ◦C. Raman spectroscopy identifies multiple sulphate symmetric stretching modes in line with the three sulphate crystallographically different sites. Raman spectroscopy also identifies a band at 1072 cm−1 attributed to a carbonate symmetric stretching mode, confirming the presence of thaumasite. The observation of multiple bands in the _4 spectral region between 700 and 550 cm−1 offers evidence for the reduction in symmetry of the sulphate anion from Td to C2v or even lower symmetry. The Raman band at 3629 cm−1 is assigned to the OH unit stretching vibration and the broad feature at around 3487 cm−1 to water stretching bands. Vibrational spectroscopy enables an assessment of the molecular structure of natural ettringite to be made.