title: A vibrational spectroscopic study of the silicate mineral ardennite-(As).
abstract: We have used a combination of scanning electron microscopy with EDX and vibrational spectroscopy to study the mineral ardennite-(As). The mineral ardennite-(As) of accepted formula Mn4(2+)(Al,Mg)6(Si3O10)(SiO4)2(AsO4,VO4)(OH)6 is a silicate mineral which may contain arsenate and/or vanadates anions. Because of the oxyanions present, the mineral lends itself to analysis by Raman and infrared spectroscopy. Qualitative chemical analysis shows a homogeneous phase, composed by Si, Mn, Al and As. Ca and V were also observed in partial substitution for Mn and As. Raman bands at 1197, 1225, 1287 and 1394 cm(-1) are assigned to SiO stretching vibrations. The strong Raman bands at 779 and 877 cm(-1) are assigned to the AsO4(3-) antisymmetric and symmetric stretching vibrations. The Raman band at 352 cm(-1) is assigned to the ν2 symmetric bending vibration. The series of Raman bands between 414 and 471 cm(-1)are assigned to the ν4 out of plane bending modes of the AsO4(3-) units. Intense Raman bands observed at 301 and 314 cm(-1) are attributed to the MnO stretching and bending vibrations. Raman bands at 3041, 3149, 3211 and 3298 cm(-1) are attributed to the stretching vibrations of OH units. There is vibrational spectroscopic evidence for the presence of water adsorbed on the ardennite-(As) surfaces.
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.forename: Andrés
authors.initials: A
authors.lastname: López
authors.forename: Yunfei
authors.initials: Y
authors.lastname: Xi
authors.forename: Ricardo
authors.initials: R
authors.lastname: Scholz
authors.forename: Antonio Luciano
authors.initials: AL
authors.lastname: Gandini
mesh_terms: D000327:Adsorption; D001151:Arsenic / Q000737:chemistry*; D008903:Minerals / Q000737:chemistry*; D017640:Silicates / Q000737:chemistry*; D013055:Spectrophotometry, Infrared; D013059:Spectrum Analysis, Raman; D014867:Water / Q000032:analysis
chemical_list: D008903:Minerals; D017640:Silicates; D014867:Water; D001151:Arsenic
keywords: Adsorbed water; Ardennite-(As); Infrared spectroscopy; Raman spectroscopy; Silicate