DEGEO - Departamento de Geologia
URI permanente desta comunidadehttp://www.hml.repositorio.ufop.br/handle/123456789/8
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Resultados da Pesquisa
Item Raman and infrared spectroscopic characterization of the arsenate-bearing mineral tangdanite– and in comparison with the discredited mineral clinotyrolite.(2013) Frost, Ray Leslie; Cipriano, Ricardo Augusto Scholz; López, AndrésTheminerals clinotyrolite and fuxiaotuite are discredited in terms of the mineral tangdanite. Themixed anionmineral tangdanite Ca2Cu9(AsO4)4(SO4)0.5(OH)9 9H2O has been studied using a combination of Raman and infrared spectroscopy. Characteristic bands associated with arsenate, sulphate and hydroxyl units are identified. Broad bands in the OH stretching region are observed and are resolved into component bands. These bands are assigned to water and hydroxyl stretching vibrations. Two intense Raman bands at 837 and approximately 734 cm 1 are assigned to the ν1 (AsO4)3 symmetric stretching and ν3 (AsO4)3 antisymmetric stretching modes. Infrared bands at 1023 cm 1 are assigned to the (SO4)2 ν1 symmetric stretching mode, and infrared bands at 1052, 1110 and 1132 cm 1 assigned to (SO4)2 ν3 antisymmetric stretching modes, confirming the presence of the sulphate anion in the tangdanite structure. Raman bands at 593 and 628 cm 1 are attributed to the (SO4)2 ν4 bending modes. Low-intensity Raman bands found at 457 and 472cm 1 are assigned to the (AsO4)3 ν2 bending modes. A comparison is made with the previously obtained spectral data on the discredited mineral clinotyrolite.Item A Raman spectroscopic study of the arsenate mineral chenevixite Cu2Fe23+(AsO4)2(OH)4-H2O.(2015) Frost, Ray Leslie; López, Andrés; Cipriano, Ricardo Augusto Scholz; Lana, Cristiano de Carvalho; Xi, YunfeiWe have studied the mineral chenevixite from Manto Cuba Mine, San Pedro de Cachiyuyo District, Inca de Oro, Chañaral Province, Atacama Region, Chile, using a combination of scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDX) and vibrational spectroscopy. Qualitative chemical analysis shows a homogeneous composition, with predominance of As, Fe, Al, Cu, Fe and Cu. Minor amounts of Si were also observed. Raman spectroscopy complimented with infrared spectroscopy has been used to assess the molecular structure of the arsenate minerals chenevixite. Characteristic Raman and infrared bands of the (AsO4)3_ stretching and bending vibrations are identified and described. The observation of multiple bands in the (AsO4)3_ bending region offers support for the loss of symmetry of the arsenate anion in the structure of chenevixite. Raman bands attributable to the OH stretching vibrations of water and hydroxyl units were analysed. Estimates of the hydrogen bond distances were made based upon the OH stretching wavenumbers.Item A vibrational spectroscopic study of the arsenate mineral bayldonite (Cu,Zn)3Pb(AsO3OH)2(OH)2 - a comparison with other basic arsenates.(2014) Frost, Ray Leslie; López, Andrés; Gonçalves, Guilherme de Oliveira; Cipriano, Ricardo Augusto Scholz; Xi, YunfeiWe have studied the vibrational spectra of the mineral bayldonite, a hydroxy arsenate of copper and lead of formula Cu3Pb(AsO3OH)2(OH)2 from the type locality, the Penberthy Croft Mine, St Hilary, Mount’s Bay District, Cornwall, England and relate the spectra to the mineral structure. Raman bands at 896 and 838 cm_1 are assigned to the ðAsO4Þ3_ m1 symmetric stretching mode and the second to the ðAsO4Þ3_ m3 antisymmetric stretching mode. It is noted that the position of the symmetric stretching mode is at a higher position than the antisymmetric stretching mode. It is proposed that the Raman bands at 889 and 845 cm_1 are symmetric and antisymmetric stretching modes of the (HOAsO3)2_ units. Raman bands of bayldonite at 490 and 500 cm_1 are assigned to the ðAsO4Þ3_ m4 bending modes. Raman bands for bayldonite are noted at 396, 408 and 429 cm_1 and are assigned to the ðAsO4Þ3_ m2 bending modes. A comparison is made with spectra of the other basic copper arsenate minerals, namely cornubite, olivenite, cornwallite.Item Structural characterization and vibrational spectroscopy of the arsenate mineral wendwilsonite.(2014) Frost, Ray Leslie; Cipriano, Ricardo Augusto Scholz; López, Andrés; Belotti, Fernanda Maria; Xi, YunfeiIn this paper, we have investigated on the natural wendwilsonite mineral with the formulae Ca2(Mg,Co)(AsO4)2_2(H2O). Raman spectroscopy complimented with infrared spectroscopy has been used to determine the molecular structure of the wendwilsonite arsenate mineral. A comparison is made with the roselite mineral group with formula Ca2B(AsO4)2_2H2O (where B may be Co, Fe2+, Mg, Mn, Ni, Zn). The Raman spectra of the arsenate related to tetrahedral arsenate clusters with stretching region shows strong differences between that of wendwilsonite and the roselite arsenate minerals which is attributed to the cation substitution for calcium in the structure. The Raman arsenate (AsO4)3_ stretching region shows strong differences between that of wendwilsonite and the roselite arsenate minerals which is attributed to the cation substitution for calcium in the structure. In the infrared spectra complexity exists of multiple to tetrahedral (AsO4)3_ clusters with antisymmetric stretching vibrations observed indicating a reduction of the tetrahedral symmetry. This loss of degeneracy is also reflected in the bending modes. Strong Raman bands around 450 cm_1 are assigned to m4 bending modes. Multiple bands in the 350–300 cm_1 region assigned to m2 bending modes provide evidence of symmetry reduction of the arsenate anion. Three broad bands for wendwilsonite found at 3332, 3119 and 3001 cm_1 are assigned to OH stretching bands. By using a Libowitzky empirical equation, hydrogen bond distances of 2.65 and 2.75 Å are estimated. Vibrational spectra enable the molecular structure of the wendwilsonite mineral to be determined and whilst similarities exist in the spectral patternsb with the roselite mineral group, sufficient differences exist to be able to determine the identification of the minerals.Item Raman spectroscopy of the arsenate minerals maxwellite and in comparison with tilasite.(2014) Frost, Ray Leslie; Cipriano, Ricardo Augusto Scholz; López, Andrés; Xi, YunfeiMaxwellite NaFe3+(AsO4)F is an arsenate mineral containing fluoride and forms a continuous series with tilasite CaMg(AsO4)F. Both maxwellite and tilasite form a continuous series with durangite NaAl3+(AsO4)- F. We have used the combination of scanning electron microscopy with EDS and vibrational spectroscopy to chemically analyse the mineral maxwellite and make an assessment of the molecular structure. Chemical analysis shows that maxwellite is composed of Fe, Na and Ca with minor amounts of Mn and Al. Raman bands for tilasite at 851 and 831 cm_1 are assigned to the Raman active m1 symmetric stretching vibration (A1) and the Raman active triply degenerate m3 antisymmetric stretching vibration (F2). The Raman band of maxwellite at 871 cm_1 is assigned to the m1 symmetric stretching vibration and the Raman band at 812 cm_1 is assigned to the m3 antisymmetric stretching vibration. The intense Raman band of tilasite at 467 cm_1 is assigned to the Raman active triply degenerate m4 bending vibration (F2). Raman band at 331 cm_1 for tilasite is assigned to the Raman active doubly degenerate m2 symmetric bending vibration (E). Both Raman and infrared spectroscopy do not identify any bands in the hydroxyl stretching region as is expected.Item Infrared and Raman spectroscopic characterization of the arsenate mineral ceruleite Cu2Al7(AsO4)4(OH)13 11.5(H2O).(2013) Frost, Ray Leslie; López, Andrés; Cipriano, Ricardo Augusto Scholz; Xi, YunfeiThe molecular structure of the arsenate mineral ceruleite has been assessed using a combination of Raman and infrared spectroscopy. The most intense band observed at 903 cm^-1 is assigned to the (AsO4)^3- symmetric stretching vibrational mode. The infrared spectrum shows intense bands at 787, 827 and 886 cm^-1, ascribed to the triply degenerate m3 antisymmetric stretching vibration. Raman bands observed at 373, 400, 417 and 430 cm^-1 are attributed to the m2 vibrational mode. Three broad bands for ceruleite found at 3056, 3198 and 3384 cm^-1 are assigned to water OH stretching bands. By using a Libowitzky empirical equation, hydrogen bond distances of 2.65 and 2.75 Å are calculated. Vibrational spectra enable the molecular structure of the ceruleite mineral to be determined and whilst similarities exist in the spectral patterns with the roselite mineral group, sufficient differences exist to be able to determine the identification of the minerals.Item A Raman and infrared spectroscopic characterisation of the phosphate mineral phosphohedyphane Ca2Pb3(PO4)3Cl from the Roote mine, Nevada, USA.(2014) Frost, Ray Leslie; Cipriano, Ricardo Augusto Scholz; López, Andrés; Souza, Bárbara Emilly Vieira Firmino e; Lana, Cristiano de Carvalho; Xi, YunfeiPhosphohedyphane Ca2Pb3(PO4)3Cl is rare Ca and Pb phosphate mineral that belongs to the apatite supergroup. We have analysed phosphohedyphane using SEM with EDX, and Raman and infrared spectroscopy. The chemical analysis shows the presence of Pb, Ca, P and Cl and the chemical formula is expressed as Ca2Pb3(PO4)3Cl. The very sharp Raman band at 975 cm^-1 is assigned to the PO4^3- v1 symmetric stretching mode. Raman bands noted at 1073, 1188 and 1226 cm^-1 are to the attributed to the PO4^3- v3 antisymmetric stretching modes. The two Raman bands at 835 and 812 cm^-1 assigned to the AsO4^3- v1 symmetric stretching vibration and AsO4^3- v3 antisymmetric stretching modes prove the substitution of As for P in the structure of phosphohedyphane. A series of bands at 557, 577 and 595 cm^-1 are attributed to the v4 out of plane bending modes of the PO4 units. The multiplicity of bands in the v2, v3 and v4 spectral regions provides evidence for the loss of symmetry of the phosphate anion in the phosphohedyphane structure. Observed bands were assigned to the stretching and bending vibrations of phosphate tetrahedra. Some Raman bands attributable to OH stretching bands were observed, indicating the presence of water and/or OH units in the structure.