title: A vibrational spectroscopic study of the silicate mineral normandite--NaCa(Mn(2+),Fe(2+))(Ti,Nb,Zr)Si2O7(O,F)2.
abstract: We have studied the mineral normandite using a combination of scanning electron microscopy with energy dispersive spectroscopy and vibrational spectroscopy. The mineral normandite NaCa(Mn(2+),Fe(2+))(Ti,Nb,Zr)Si2O7(O,F)2 is a crystalline sodium calcium silicate which contains rare earth elements. Chemical analysis shows the mineral contains a range of elements including Na, Mn(2+), Ca, Fe(2+) and the rare earth element niobium. No Raman bands are observed above 1100 cm(-1). The mineral is characterised by Raman bands observed at 724, 748, 782 and 813 cm(-1). Infrared bands are broad; nevertheless bands may be resolved at 723, 860, 910, 958, 933, 1057 and 1073 cm(-1). Intense Raman bands at 454, 477 and 513 cm(-1) are attributed to OSiO bending modes. No Raman bands are observed in the hydroxyl stretching region, but low intensity infrared bands are observed at 3191 and 3450 cm(-1). This observation brings into question the true formula of the mineral.
authors.affiliation: School of Chemistry, Physics and Mechanical Engineering, Science and Engineering Faculty, Queensland University of Technology, GPO Box 2434, Brisbane, Queensland 4001, Australia. Electronic address: r.frost@qut.edu.au.
authors.forename: Ray L
authors.initials: RL
authors.lastname: Frost
authors.affiliation: School of Chemistry, Physics and Mechanical Engineering, Science and Engineering Faculty, Queensland University of Technology, GPO Box 2434, Brisbane, Queensland 4001, Australia.
authors.forename: Andrés
authors.initials: A
authors.lastname: López
authors.affiliation: School of Chemistry, Physics and Mechanical Engineering, Science and Engineering Faculty, Queensland University of Technology, GPO Box 2434, Brisbane, Queensland 4001, Australia.
authors.forename: Frederick L
authors.initials: FL
authors.lastname: Theiss
authors.affiliation: Geology Department, School of Mines, Federal University of Ouro Preto, Campus Morro do Cruzeiro, Ouro Preto, MG 35400-00, Brazil.
authors.forename: Ricardo
authors.initials: R
authors.lastname: Scholz
authors.affiliation: Geology Department, Federal University of Minas Gerais, Belo Horizonte, MG 31270-901, Brazil.
authors.forename: Antônio Wilson
authors.initials: AW
authors.lastname: Romano
mesh_terms: D008903:Minerals / Q000737:chemistry*; D017640:Silicates / Q000737:chemistry*; D017655:Silicon Compounds / Q000737:chemistry*; D013052:Spectrometry, X-Ray Emission; D013055:Spectrophotometry, Infrared; D013059:Spectrum Analysis, Raman; D014732:Vibration
chemical_list: D008903:Minerals; D017640:Silicates; D017655:Silicon Compounds
keywords: Calcium; Molecular structure; Normandite; Raman spectroscopy; Rare earth elements; Silicate