Vibrational spectroscopy of the sulphate mineral sturmanite from Kuruman manganese deposits, South Africa

Frost, Ray L., Scholz, Ricardo, López, Andrés, Xi, Yunfei, & Lana, Cristiano (2014) Vibrational spectroscopy of the sulphate mineral sturmanite from Kuruman manganese deposits, South Africa. Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 133, pp. 24-30.

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Abstract

The mineral sturmanite is a hydrated calcium iron aluminium manganese sulphate tetrahydroxoborate hydroxide of formula Ca6(Fe, Al, Mn)2(SO4)2(B(OH)4)(OH)12•26H2O. We have studied the mineral sturmanite using a number of techniques, including SEM with EPMA and vibrational spectroscopy. Chemical analysis shows a homogeneous phase, composed by Ca, Fe, Mn, S, Al and Si. B is not determined in this EPMA technique. An intense Raman band at 990 cm−1 is assigned to the SO42− symmetric stretching mode. Raman spectroscopy identifies multiple sulphate symmetric stretching modes in line with the three sulphate crystallographically different sites. Raman spectroscopy also identifies a band at 1069 cm−1 which may be attributed to a carbonate symmetric stretching mode, indicating the presence of thaumasite. Infrared spectra display two bands at 1080 and 1107 cm−1 assigned to the SO42− antisymmetric stretching modes. The observation of multiple bands in this ν4 spectral region offers evidence for the reduction in symmetry of the sulphate anion from Td to C2v or even lower symmetry. The Raman band at 3622 cm−1 is assigned to the OH unit stretching vibration and the broad feature at around 3479 cm−1 to water stretching bands. Infrared spectroscopy shows a set of broad overlapping bands in the OH stretching region. Vibrational spectroscopy enables an assessment of the molecular structure of sturmanite to be made.

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ID Code: 72861
Item Type: Journal Article
Refereed: Yes
Keywords: Raman spectroscopy, Sturmanite, Borate, Kuruman, Infrared spectroscopy, Thermal analysis
DOI: 10.1016/j.saa.2014.04.115
ISSN: 13861425
Subjects: Australian and New Zealand Standard Research Classification > CHEMICAL SCIENCE (030000) > PHYSICAL CHEMISTRY (INCL. STRUCTURAL) (030600) > Structural Chemistry and Spectroscopy (030606)
Divisions: Current > Schools > School of Chemistry, Physics & Mechanical Engineering
Current > QUT Faculties and Divisions > Science & Engineering Faculty
Copyright Owner: Copyright 2014 Elsevier B.V.
Copyright Statement: NOTICE: this is the author’s version of a work that was accepted for publication in Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy. Changes resulting from the publishing process, such as peer review, editing, corrections, structural formatting, and other quality control mechanisms may not be reflected in this document. Changes may have been made to this work since it was submitted for publication. A definitive version was subsequently published in Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, [Volume 133, (10 December 2014)] DOI: 10.1016/j.saa.2014.04.115
Deposited On: 17 Jun 2014 22:37
Last Modified: 13 Dec 2016 07:06

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