DEGEO - Departamento de Geologia
URI permanente desta comunidadehttp://www.hml.repositorio.ufop.br/handle/123456789/8
Navegar
4 resultados
Resultados da Pesquisa
Item Infrared and Raman spectroscopic characterization of the silicate mineral olmiite CaMn^2+[SiO3(OH)](OH) – implications for the molecular structure.(2013) Frost, Ray Leslie; Cipriano, Ricardo Augusto Scholz; López, Andrés; Xi, Yunfei; Granja, Amanda; Gobac, Željka Žigovečki; Lima, Rosa Malena FernandesWe have studied the mineral olmiite CaMn[SiO3(OH)](OH) which forms a series with its calcium analogue poldervaartite CaCa[SiO3(OH)](OH) using a range of techniques including scanning electron microscopy, thermogravimetric analysis, Raman and infrared spectroscopy. Chemical analysis shows the mineral is purê and contains only calcium and manganese in the formula. Thermogravimetric analysis proves the mineral decomposes at 502 °C with a mass loss of 8.8% compared with the theoretical mass loss of 8.737%. A strong Raman band at 853 cm^-1 is assigned to the SiO stretching vibration of the SiO3(OH) units. Two Raman bands at 914 and 953 cm^-1 are attributed to the antisymmetric vibrations. Two intense Raman bands observed at 3511 and 3550 cm^-1are assigned to the OH stretching vibration of the SiO3(OH) units. The observation of multiple OH bands supports the concept of the non-equivalence of the OH units. Vibrational spectroscopy enables a detailed assessment of the molecular structure of olmiite.Item Raman and infrared spectroscopic characterization of the phosphate mineral paravauxite Fe2+Al2(PO4)2(OH)2. 8H2O.(2013) Frost, Ray Leslie; Cipriano, Ricardo Augusto Scholz; López, Andrés; Xi, Yunfei; Gobac, Željka ŽigovečkiWe have undertaken a vibrational spectroscopic study of paravauxite the Siglo XX mine, Bustillo Province, northern of Potosí department, Bolivia. This mine is important source for rare and unusual secondary phosphate minerals and is the type locality for a number of rare phosphates such as vauxite, sigloite, metavauxite and for jeanbandyite. The chemical formula of the studied sample was determined as Fe^2+0,95; (Al0:07)R1:02ðAlÞ2:09ðPO4Þ1:97ðOHÞ1:98.7:90(H2O).The Raman spectrum is dominated by an intense Raman band at 1020 cm^-1assigned to the PO4^-3 m1symmetric stretching mode. Low intensity Raman bands found at 1058, 1115 and 1148 cm^-1 are assigned to the PO4^-3 m3 antisymmetric stretching vibrations. Raman bands of paravauxite at 537, 570, 609 and 643 cm^-1 are assigned to the m4 PO4^-3 bending modes whilst the Raman bands at 393 and 420 cm^-1are due to the m2 PO4^-3 bending modes. The Raman spectral profile of paravauxite in the hydroxyl stretching region is broad with component bands resolved at 3086, 3215, 3315, 3421, 3505 and 3648 cm^-1. Vibrational spectroscopy enables the assessment of the molecular structure of paravauxite to be undertaken.Item Vibrational spectroscopy of the borate mineral gaudefroyite Ca4Mn3-x3+ (BO3)3 (CO3) (O;OH) from N’Chwaning II mine, Kalahari, Republic of South Africa.(2013) Frost, Ray Leslie; Cipriano, Ricardo Augusto Scholz; López, Andrés; Xi, Yunfei; Gobac, Željka Žigovečki; Lana, Cristiano de CarvalhoGaudefroyite Ca4Mn3-x^3+ (BO3)3 (CO3) (O;OH) is an unusual mineral containing both borate and carbonate groups and is found in the oxidation zones of manganese minerals, and it is black in color. Vibrational spectroscopy has been used to explore the molecular structure of gaudefroyite. Gaudefroyite crystals are short dipyramidal or prismatic with prominent pyramidal terminations, to 5 cm. Two very sharp Raman bands at 927 and 1076 cm^-1 are assigned to trigonal borate and carbonate respectively. Broad Raman bands at 1194, 1219 and 1281 cm^-1 are attributed to BOH in-plane bending modes. Raman bands at 649 and 670 cm^-1 are assigned to the bending modes of trigonal and tetrahedral boron. Infrared spectroscopy supports these band assignments. Raman bands in the OH stretching region are of a low intensity. The combination of Raman and infrared spectroscopy enables the assessment of the molecular structure of gaudefroyite to be made.Item Characterization of the sulphate mineral coquimbite, a secondary iron sulphate from Javier Ortega mine, Lucanas Province, Peru – Using infrared, Raman spectroscopy and thermogravimetry.(2014) Frost, Ray Leslie; Gobac, Željka Žigovečki; López, Andrés; Xi, Yunfei; Cipriano, Ricardo Augusto Scholz; Lana, Cristiano de Carvalho; Lima, Rosa Malena FernandesThe mineral coquimbite has been analysed using a range of techniques including SEM with EDX, thermal analytical techniques and Raman and infrared spectroscopy. The mineral originated from the Javier Ortega mine, Lucanas Province, Peru. The chemical formula was determined as (Fe1.37^3+; Al0.63)Σ2.00(SO4)3. 9H2O. Thermal analysis showed a total mass loss of ~73.4% on heating to 1000 °C. A mass loss of 30.43% at 641.4 °C is attributed to the loss of SO3. Observed Raman and infrared bands were assigned to the stretching and bending vibrations of sulphate tetrahedra, aluminium oxide/hydroxide octahedra, water molecules and hydroxyl ions. The Raman spectrum shows well resolved bands at 2994, 3176, 3327, 3422 and 3580 cm^-1 attributed to water stretching vibrations. Vibrational spectroscopy combined with thermal analysis provides insight into the structure of coquimbite.