title: Characterization of the sulphate mineral amarantite - Fe2(3+)(SO4)O·7H2O using infrared, Raman spectroscopy and thermogravimetry.
abstract: The mineral amarantite Fe2(3+)(SO4)O·7H2O has been studied using a combination of techniques including thermogravimetry, electron probe analyses and vibrational spectroscopy. Thermal analysis shows decomposition steps at 77.63, 192.2, 550 and 641.4°C. The Raman spectrum of amarantite is dominated by an intense band at 1017 cm(-1) assigned to the SO4(2-) ν1 symmetric stretching mode. Raman bands at 1039, 1054, 1098, 1131, 1195 and 1233 cm(-1) are attributed to the SO4(2-) ν3 antisymmetric stretching modes. Very intense Raman band is observed at 409 cm(-1) with shoulder bands at 399, 451 and 491 cm(-1) are assigned to the ν2 bending modes. A series of low intensity Raman bands are found at 543, 602, 622 and 650 cm(-1) are assigned to the ν4 bending modes. A very sharp Raman band at 3529 cm(-1) is assigned to the stretching vibration of OH units. A series of Raman bands observed at 3025, 3089, 3227, 3340, 3401 and 3480 cm(-1) are assigned to water bands. Vibrational spectroscopy enables aspects of the molecular structure of the mineral amarantite to be ascertained.
authors.affiliation: School of Chemistry, Physics and Mechanical Engineering, Science and Engineering Faculty, Queensland University of Technology, Brisbane, Queensland 4001, Australia. r.frost@qut.edu.au
authors.forename: Ray L
authors.initials: RL
authors.lastname: Frost
authors.forename: Andrés
authors.initials: A
authors.lastname: López
authors.forename: Ricardo
authors.initials: R
authors.lastname: Scholz
authors.forename: Yunfei
authors.initials: Y
authors.lastname: Xi
authors.forename: Aléssio J
authors.initials: AJ
authors.lastname: da Silveira
authors.forename: Rosa Malena Fernandes
authors.initials: RM
authors.lastname: Lima
mesh_terms: D058085:Iron Compounds / Q000737:chemistry*; D008903:Minerals / Q000737:chemistry*; D013055:Spectrophotometry, Infrared; D013059:Spectrum Analysis, Raman; D013431:Sulfates / Q000737:chemistry*; D013818:Thermogravimetry
chemical_list: D058085:Iron Compounds; D008903:Minerals; D013431:Sulfates
keywords: Amarantite; Evaporite; Infrared spectroscopy; Raman spectroscopy; Sulphate