DEGEO - Departamento de Geologia
URI permanente desta comunidadehttp://www.hml.repositorio.ufop.br/handle/123456789/8
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Resultados da Pesquisa
Item Vibrational spectroscopic characterization of the phosphate mineral ludlamite (Fe,Mn,Mg)3(PO4)2 4H2O - a mineral found in lithium bearing pegmatites.(2013) Frost, Ray Leslie; Xi, Yunfei; Cipriano, Ricardo Augusto Scholz; Belotti, Fernanda MariaThe objective of this work is to analyze ludlamite (Fe,Mn,Mg)3(PO4)2_4H2O from Boa Vista mine, Galiléia, Brazil and to assess the molecular structure of the mineral. The phosphate mineral ludlamite has been characterized by EMP-WDS, Raman and infrared spectroscopic measurements. The mineral is shown to be a ferrous phosphate with some minor substitution of Mg and Mn. Raman bands at 917 and 950 cm_1 are assigned to the symmetric stretching mode of HOPO2_ 3 and PO3_ 4 units. Raman bands at 548, 564, 599 and 634 cm_1 are assigned to the m4 PO3_ 4 bending modes. Raman bands at 2605, 2730, 2896 and 3190 cm_1 and infrared bands at 2623, 2838, 3136 and 3185 cm_1 are attributed to water stretching vibrations. By using a Libowitzky empirical function, hydrogen bond distances are calculated from the OH stretching wavenumbers. Strong hydrogen bonds in the structure of ludlamite are observed as determined by their hydrogen bond distances. The application of infrared and Raman spectroscopy to the study of ludlamite enables the molecular structure of the pegmatite mineral ludlamite to be assessed.Item Infrared and Raman spectroscopic characterization of the phosphate mineral fairfieldite Ca2(Mn2+,Fe2+)2(PO4)2 2(H2O).(2013) Frost, Ray Leslie; Xi, Yunfei; Cipriano, Ricardo Augusto Scholz; Belotti, Fernanda Maria; López, AndrésRaman spectroscopy complimented with infrared spectroscopy has been used to determine the molecular structure of the phosphate mineral fairfieldite. The Raman phosphate ðPO4Þ3_ stretching region shows strong differences between the fairfieldite phosphate minerals which is attributed to the cation substitution for calcium in the structure. In the infrared spectra complexity exists with multiple ðPO4Þ2_ 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 600 cm_1 are assigned to m4 phosphate bending modes. Multiple bands in the 400–450 cm_1 region assigned to m2 phosphate bending modes provide further evidence of symmetry reduction of the phosphate anion. Three broadbands for fairfieldite are found at 3040, 3139 and 3271 cm_1 and are assigned to OH stretching bands. By using a Libowitzky empirical equation hydrogen bond distances of 2.658 and 2.730 Å are estimated. Vibrational spectroscopy enables aspects of the molecular structure of the fairfieldite to be ascertained.Item Vibrational spectroscopy of the phosphate mineral lazulite - (Mg, Fe)Al2(PO4)2 (OH)2 found in the Minas Gerais, Brazil.(2013) Frost, Ray Leslie; Xi, Yunfei; Beganovic, Martina; Belotti, Fernanda Maria; Cipriano, Ricardo Augusto ScholzThis research was done on lazulite samples from the Gentil mine, a lithium bearing pegmatite located in the municipality of Mendes Pimentel, Minas Gerais, Brazil. Chemical analysis was carried out by electron microprobe analysis and indicated a magnesium rich phase with partial substitution of iron. Traces of Ca and Mn, (which partially replaced Mg) were found. The calculated chemical formula of the studied sample is: (Mg0.88, Fe0.11)Al1.87(PO4)2.08(OH)2.02. The Raman spectrum of lazulite is dominated by an intense Sharp band at 1060 cm_1 assigned to PO stretching vibrations of of tetrahedral [PO4] clusters presents into the HPO2_ 4 units. Two Raman bands at 1102 and 1137 cm_1 are attributed to both the HOP and PO antisymmetric stretching vibrations. The two infrared bands at 997 and 1007 cm_1 are attributed to the m1 PO3_ 4 symmetric stretching modes. The intense bands at 1035, 1054, 1081, 1118 and 1154 cm_1 are assigned to the m3 PO3_ 4 antisymmetric stretching modes from both the HOP and tetrahedral [PO4] clusters. A set of Raman bands at 605, 613, 633 and 648 cm_1 are assigned to the m4 out of plane bending modes of the PO4, HPO4 and H2PO4 units. Raman bands observed at 414, 425, 460, and 479 cm_1 are attributed to the m2 tetrahedral PO4 clusters, HPO4 and H2PO4 bending modes. The intense Raman band at 3402 and the infrared band at 3403 cm_1 are assigned to the stretching vibration of the OH units. A combination of Raman and infrared spectroscopy enabled aspects of the molecular structure of the mineral lazulite to be understood.Item Assessment of the molecular structure of natrodufrénite – NaFe^2+Fe^3+(PO4)4(OH)6.2(H2O), a secondary pegmatite phosphate mineral from Minas Gerais, Brazil.(2013) López, Andrés; Frost, Ray Leslie; Xi, Yunfei; Cipriano, Ricardo Augusto Scholz; Belotti, Fernanda Maria; Ribeiro, ÉrikaThe mineral natrodufrénite a secondary pegmatite phosphate mineral from Minas Gerais, Brazil, has been studied by a combination of scanning electron microscopy and vibrational spectroscopic techniques. Electron probe analysis shows the formula of the studied mineral as(Na0.88Ca0.12)P1.00(Fe2þ0:72Mn0.11Mg0.08Ca0.04Zr0.01Cu0.01)P0.97 (Fe3þ4:89Al0.02)P4.91(PO4)3.96(OH6.15F0.07)6.22.2.05(H2O). Raman spectroscopy identifies an intense peak at 1003 cm^-1 assigned to the PO4^-3 m1 symmetric stretching mode. Raman bands are observed at 1059 and 1118 cm^-1 and are attributed to the PO4^-3 m3 antisymmetric stretching vibrations. A comparison is made with the spectral data of other hydrate hydroxy phosphateminerals including cyrilovite andwardite. Raman bands at560, 582,619 and 668 cm^-1 are assigned tothe m4PO3 4 bendingmodes and Ramanbands at425,444, 477 and 507 cm^-1 are due to the m2PO3 4 bendingmodes. Raman bands inthe 2600–3800 cm^-1 spectral range are attributed towater and OH stretching vibrations. Vibrational spectroscopy enables aspects of themolecular structure of natrodufrénite to be assessed..Item Vibrational spectroscopic characterization of the phosphate mineral bermanite Mn2+Mn23+(PO4)2(OH)2 4(H2O).(2012) Frost, Ray Leslie; Xi, Yunfei; Cipriano, Ricardo Augusto Scholz; Belotti, Fernanda MariaBermanite Mn^2+Mn2^3+(PO4)2(OH)2.4(H2O) is a mixed valent hydrated hydroxy phosphate mineral. The mineral is reddish-brown and occurs in crystal aggregates and as lamellar masses. Bermanite is a common mineral in granitic pegmatites. The chemical composition of bermanite was obtained using EDS techniques. We have studied the molecular structure of bermanite using vibrational spectroscopy. The mineral is characterized by a Raman doublet at 991 and 999 cm^-1 attributed to the phosphate stretching mode of two non-equivalent phosphate units. Raman bands at 1071, 1117 and 1142 cm^-1 are assigned to the phosphate antisymmetric stretching modes. The hydroxyl stretching spectral region is complex with overlapping bands attributed to water and hydroxyl stretching vibrations. Vibrational spectroscopy proves most useful for the study of the mineral bermanite.Item Raman and infrared spectroscopic characterization of beryllonite, a sodium and beryllium phosphate mineral - implications for mineral collectors.(2012) Frost, Ray Leslie; Xi, Yunfei; Cipriano, Ricardo Augusto Scholz; Belotti, Fernanda Maria; Menezes Filho, Luiz Alberto DiasThe mineral beryllonite has been characterized by the combination of Raman spectroscopy and infrared spectroscopy. SEM–EDX was used for the chemical analysis of the mineral. The intense sharp Raman band at 1011 cm_1, was assigned to the phosphate symmetric stretching mode. Raman bands at 1046, 1053, 1068 and the low intensity bands at 1147, 1160 and 1175 cm_1 are attributed to the phosphate antisymmetric stretching vibrations. The number of bands in the antisymmetric stretching region supports the concept of symmetry reduction of the phosphate anion in the beryllonite structure. This concept is supported by the number of bands found in the out-of-plane bending region. Multiple bands are also found in the in-plane bending region with Raman bands at 399, 418, 431 and 466 cm_1. Strong Raman bands at 304 and 354 cm_1 are attributed to metal oxygen vibrations. Vibrational spectroscopy served to determine the molecular structure of the mineral. The pegmatitic phosphate minerals such as beryllonite are more readily studied by Raman spectroscopy than infrared spectroscopy.