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 althausite Mg2(PO4)(OH,F,O) - implications for the molecular structure.(2014) Frost, Ray Leslie; López, Andrés; Xi, Yunfei; Cipriano, Ricardo Augusto ScholzNatural single-crystal specimens of althausite from Brazil, with general formula Mg2(PO4)(OH,F,O) were investigated by Raman and infrared spectroscopy. The mineral occurs as a secondary product in granitic pegmatites. The Raman spectrum of althausite is characterized by bands at 1020, 1033 and 1044 cm_1, assigned to m1 symmetric stretching modes of the HOPO3_ 3 and PO3_ 4 units. Raman bands at around 1067, 1083 and 1138 cm_1 are attributed to both the HOP and PO antisymmetric stretching vibrations. The set of Raman bands observed at 575, 589 and 606 cm_1 are assigned to the m4 out of plane bending modes of the PO4 and H2PO4 units. Raman bands at 439, 461, 475 and 503 cm_1 are attributed to the m2 PO4 and H2PO4 bending modes. Strong Raman bands observed at 312, 346 cm_1 with shoulder bands at 361, 381 and 398 cm_1 are assigned to MgO stretching vibrations. No bands which are attributable to water were found. Vibrational spectroscopy enables aspects of the molecular structure of althausite to be assessed.Item Vibrational spectroscopy of the phosphate mineral kovdorskite - Mg2PO4(OH)-3H2O.(2013) Frost, Ray Leslie; López, Andrés; Xi, Yunfei; Granja, Amanda; Cipriano, Ricardo Augusto Scholz; Lima, Rosa Malena FernandesThe mineral kovdorskite Mg2PO4(OH)_3H2O was studied by electron microscopy, thermal analysis and vibrational spectroscopy. A comparison of the vibrational spectroscopy of kovdorskite is made with other magnesium bearing phosphate minerals and compounds. Electron probe analysis proves the mineral is very pure. The Raman spectrum is characterized by a band at 965 cm_1 attributed to the PO3_ 4 m1 symmetric stretching mode. Raman bands at 1057 and 1089 cm_1 are attributed to the PO3_ 4 m3 antisymmetric stretching modes. Raman bands at 412, 454 and 485 cm_1 are assigned to the PO3_ 4 m2 bending modes. Raman bands at 536, 546 and 574 cm_1 are assigned to the PO3_ 4 m4 bending modes. The Raman spectrum in the OH stretching region is dominated by a very sharp intense band at 3681 cm_1 assigned to the stretching vibration of OH units. Infrared bands observed at 2762, 2977, 3204, 3275 and 3394 cm_1 are attributed to water stretching bands. Vibrational spectroscopy shows that no carbonate bands are observed in the spectra; thus confirming the formula of the mineral as Mg2PO4(OH)_3H2O.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 The molecular structure of matioliite NaMgAl5(PO4)4(OH)6 2(H2O) - a pegmatite mineral from Minas Gerais, Brazil.(2013) Cipriano, Ricardo Augusto Scholz; Xi, Yunfei; Frost, Ray LeslieDetailed spectroscopic and chemical investigation of matioliite, including infrared and Raman spectroscopy, scanning electron microscopy and electron probe microanalysis has been carried out on homogeneous samples from the Gentil pegmatite, Mendes Pimentel, Minas Gerais, Brazil. The chemical composition is (wt.%): FeO 2.20, CaO 0.05, Na2O 1.28, MnO 0.06, Al2O3 39.82, P2O5 42.7, MgO 4.68, F 0.02 and H2O 9.19; total 100.00. The mineral crystallize in the monoclinic crystal system, C2/c space group, with a = 25.075(1) Å, b = 5.0470(3) Å, c = 13.4370(7) Å, b = 110.97(3)_, V = 1587.9(4) Å3, Z = 4. Raman spectroscopy coupled with infrared spectroscopy supports the concept of phosphate, hydrogen phosphate and dihydrogen phosphate units in the structure of matioliite. Infrared and Raman bands attributed to water and hydroxyl stretching modes are identified. Vibrational spectroscopy adds useful information to the molecular structure of matioliite.Item The molecular structure of the phosphate mineral senegalite Al2(PO4)(OH)3-3H2O - a vibrational spectroscopic study.(2013) Frost, Ray Leslie; López, Andrés; Xi, Yunfei; Murta, Natália; Cipriano, Ricardo Augusto ScholzWe have studied the mineral senagalite, a hydrated hydroxy phosphate of aluminium with formula Al2(-PO4)(OH)3_3H2O using a combination of electron microscopy and vibrational spectroscopy. Senegalite crystal aggregates shows tabular to prismatic habitus and orthorhombic form. The Raman spectrum is dominated by an intense band at 1029 cm_1 assigned to the PO3_ 4 m1 symmetric stretching mode. Intense Raman bands are found at 1071 and 1154 cm_1 with bands of lesser intensity at 1110, 1179 and 1206 cm_1 and are attributed to the PO3_ 4 m3 antisymmetric stretching vibrations. The infrared spectrum shows complexity with a series overlapping bands. A comparison is made with spectra of other aluminium containing phosphate minerals such as augelite and turquoise. Multiple bands are observed for the phosphate bending modes giving support for the reduction of symmetry of the phosphate anion. Vibrational spectroscopy offers a means for the assessment of the structure of senagalite.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 series eosphorite-childrenite-(Mn,Fe)Al(PO4)(OH)2 (H2O).(2013) Frost, Ray Leslie; Xi, Yunfei; Cipriano, Ricardo Augusto Scholz; López, Andrés; Lima, Rosa Malena Fernandes; Ferreira, Claudiane MoraesThe phosphate mineral series eosphorite–childrenite–(Mn,Fe)Al(PO4)(OH)2•(H2O) has been studied using a combination of electron probe analysis and vibrational spectroscopy. Eosphorite is the manganese rich mineral with lower iron content in comparison with the childrenite which has higher iron and lower manganese content. The determined formulae of the two studied minerals are: (Mn0.72,Fe0.13,Ca0.01)(Al)1.04(PO4, OHPO3)1.07(OH1.89,F0.02)•0.94(H2O) for SAA-090 and (Fe0.49,Mn0.35,Mg0.06,Ca0.04)(Al)1.03(PO4, OHPO3)1.05(OH)1.90•0.95(H2O) for SAA-072. Raman spectroscopy enabled the observation of bands at 970 cm−1 and 1011 cm−1 assigned to monohydrogen phosphate, phosphate and dihydrogen phosphate units. Differences are observed in the area of the peaks between the two eosphorite minerals. Raman bands at 562 cm−1, 595 cm−1, and 608 cm−1 are assigned to the _4 bending modes of the PO4, HPO4 and H2PO4 units; Raman bands at 405 cm−1, 427 cm−1 and 466 cm−1 are attributed to the _2 modes of these units. Raman bands of the hydroxyl and water stretching modes are observed. Vibrational spectroscopy enabled details of the molecular structure of the eosphorite mineral series to be determined.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.