DEGEO - Departamento de Geologia
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73 resultados
Resultados da Pesquisa
Item Assessment of the molecular structure of an intermediate member of the triplite-zwieselite mineral series : a raman and infrared study.(2014) Frost, Ray Leslie; Xi, Yunfei; López, Andrés; Moreira, Viviane Amaral; Cipriano, Ricardo Augusto Scholz; Lima, Rosa Malena Fernandes; Gandini, Antônio LucianoThe mineral series triplite-zwieselite with theoretical formula (Mn2þ)2(PO4)(F)-(Fe2þ)2(PO4)(F) from the El Criolo granitic pegmatite, located in the Eastern Pampean Ranges of Cordoba Province, was studied using electron microprobe, thermogravimetry, and Raman and infrared spec- troscopy. The analysis of the mineral provided a formula of (Fe1.00, Mn0.85, Ca0.08, Mg0.06)P2.00(PO4)1.00(F0.80, OH0.20)P1.00. An intense Raman band at 981cm1 with a shoulder at 977cm1 is assigned to the PO3 4 n1 symmetric stretching mode. The observation of two bands for the phosphate symmetric stretching mode offers support for the concept that the phosphate units in the structure of triplite-zwieselite are not equivalent. Low-intensity Raman bands at 1012, 1036, 1071, 1087, and 1127 cm1 are assigned to the PO3 4 n3 antisymmetric stretching modes. A set of Raman bands at 572, 604, 639, and 684 cm1 are attributed to the PO3 4 n4 out-of-plane bending modes. A single intense Raman band is found at 3508 cm1 and is assigned to the stretching vibration of hydroxyl units. Infrared bands are observed at 3018, 3125, and 3358 cm1 and are attributed to water stretching vibrations. Supplemental materials are available for this article. Go to the publisher’s online edition of Spectroscopy Letters to view the supplemental file.Item Vibrational spectroscopic study of the phosphate mineral kryzhanovskite and in comparison with reddingite-implications for the molecular structure.(2016) Frost, Ray Leslie; Cipriano, Ricardo Augusto Scholz; Wang, LinaWe have studied the phosphate mineral kryzhanovskite (Fe3þ,Mn2þ)3(PO4)2(OH,H2O) which is a member of the phosphoferrite mineral group using a combination of scanning electron microscopy with energy dispersive spectroscopy and Raman and infrared spectroscopy. Chemical analysis shows the presence of P, Mn and Fe and confirms the formula given above. The presence of hydroxyl units in the structure is indicative of ferric iron in the formula that is an oxidised product. Raman spectroscopy coupled with infrared spectroscopy supports the concept of phosphate, hydrogen phosphate and dihydrogen phosphate units in the structure of kryzhanovskite -phosphoferrite. Infrared and Raman bands attributed to water and hydroxyl stretching modes are identified. Vibrational spectroscopy adds useful information to the molecular structure of kryzhanovskite -phosphoferrite.Item A vibrational spectroscopic study of the silicate mineral kornerupine.(2015) Frost, Ray Leslie; López, Andrés; Cipriano, Ricardo Augusto ScholzWe have studied the mineral kornerupine a boro-silicate mineral by using a combination of scanning electron microscopy with energy dispersive analysis and Raman and infrared spectroscopy. Qualitative chemical analysis of kornerupine shows a magnesium-aluminium silicate. Strong Raman bands at 925, 995 and 1051 cm-1 with bands of lesser intensity at 1035 and 1084 cm-1 are assigned to the silicon-oxygen stretching vibrations of the siloxane units. Raman bands at 923 and 947 cm-1 are attributed to the symmetrical stretching vibrations of trigonal boron. Infrared spectra show greater complexity and the infrared bands are more difficult to assign. Two intense Raman bands at 3547 and 3612 cm-1 are assigned to the stretching vibrations of hydroxyl units. In the infrared bands are observed at 3544 and 3610 cm-1. Water is also identified in the spectra of kornerupine.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 Vibrational spectroscopy of the borate mineral olshanskyite Ca3[B(OH)4]4(OH)2.(2013) Frost, Ray Leslie; Xi, Yunfei; Cipriano, Ricardo Augusto Scholz; Pereira, Matheus da Costa AlvesThe mineral olshanskyite is one of many calcium borate minerals which has never been studied using vibrational spectroscopy. The mineral is unstable and decomposes upon exposure to an electron beam. This makes the elemental analysis using EDX techniques difficult. Both the Raman and infrared spectra show complexity due to the complexity of the structure. Intense Raman bands are found at 989, 1,003, 1,025 and 1,069 cm-1 with a shoulder at 961 cm-1 and are assigned to trigonal borate units. The Raman bands at 1,141, 1,206 and 1,365 cm-1 are assigned to OH in-plane bending of BOH units. A series of Raman bands are observed in the 2,900–3,621 cm-1 spectral range and are assigned to the stretching vibrations of OH and water. This complexity is also reflected in the infrared spectra. Vibrational spectroscopy enables aspects of the structure of olshanskyite to be elucidated.Item Rockbridgeite inclusion in rock crystal from Galileia region, Minas Gerais, Brazil.(2013) Faulstich, Fabiano Richard Leite; Schnellrath, Jurgen; Oliveira, Luiz F. C. de; Cipriano, Ricardo Augusto ScholzA set of rock crystals with pleochroic inclusions were analyzed by optical microscopy, scanning electron microscopy, Raman spectroscopy and energy-dispersive spectrometry (EDS). The inclusions occur in fracture planes, have a discoid form with radial and concentric structure, diameters ranging from a few micrometers to several millimeters and thicknesses smaller than 50 mm. They have a pronounced pleochroism ranging from yellow to green when fresh and a brown color when oxidized. The Raman spectrum of the inclusion is characterized by a set of bands associated to the n1 and n3 PO4 tetrahedra stretching region (at 1186, 1137, 1061, 981 and 937 cm 1), overlapping bands associated to the n2 and n4 bending phosphate tetrahedra (at 638, 616, 576 and 463 cm 1), a suite of overlapping vibrations of XO6 octahedra (382, 333, 299 and 241 cm 1), a broad band between 3000 and 3500 cm 1 associated to the OH stretching vibration of molecular water and a sharp band at 3575 cm 1 corresponding to the stretching vibrations of OH groups. The spectrum and compositional data indicating iron, manganese and phosphorous as the main elements point to rockbridgeite, with the empirical formula (Fe2þ, Mn2þ)Fe3þ 4(PO4)3(OH)5 and an Fe2þ:Mn2þ ratio close to 1.Item A Raman and infrared spectroscopic study of the phosphate mineral laueite.(2016) Frost, Ray Leslie; Cipriano, Ricardo Augusto Scholz; López, AndrésA laueite mineral sample from Lavra Da Ilha, Minas Gerais, Brazil has been studied by vibrational spectroscopy and scanning electron microscopy with EDX. Chemical formula calculated on the basis of semi-quantitative chemical analysis can be expressed as (Mn2+0.85,Fe2+0.10Mg0.05)P1.00(Fe3+1.90,Al0.10)P2.00(PO4)2(OH)2_8H2O. The laueite structure is based on an infinite chains of vertex-linked oxygen octahedra, with Fe3+ occupying the octahedral centers, the chain oriented parallel to the c-axis and linked by PO4 groups. Consequentially not all phosphate units are identical. Two intense Raman bands observed at 980 and 1045 cm_1 are assigned to the n1 PO43_ symmetric stretching mode. Intense Raman bands are observed at 525 and 551 cm_1 with a shoulder at 542 cm_1 are assigned to the n4 out of plane bending modes of the PO43_. The observation of multiple bands supports the concept of non-equivalent phosphate units in the structure. Intense Raman bands are observed at 3379 and 3478 cm_1 and are attributed to the OH stretching vibrations of the hydroxyl units. Intense broad infrared bands are observed. Vibrational spectroscopy enables subtle details of the molecular structure of laueite to be determined.Item A SEM, EDS and vibrational spectroscopic study of the tellurite mineral : sonoraite Fe3+Te4+O3(OH) H2O.(2015) Frost, Ray Leslie; López, Andrés; Cipriano, Ricardo Augusto ScholzWe have undertaken a study of the tellurite mineral sonorite using electron microscopy with EDX combined with vibrational spectroscopy. Chemical analysis shows a homogeneous composition, with predominance of Te, Fe, Ce and In with minor amounts of S. Raman spectroscopy has been used to study the mineral sonoraite an examples of group A(XO3), with hydroxyl and water units in the mineral structure. The free tellurite ion has C3v symmetry and four modes, 2A1 and 2E. An intense Raman band at 734 cm 1 is assigned to the m1 (TeO3)2 symmetric stretching mode. A band at 636 cm 1 is assigned to the m3 (TeO3)2 antisymmetric stretching mode. Bands at 350 and 373 cm 1 and the two bands at 425 and 438 cm 1 are assigned to the (TeO3)2 m2 (A1) bending mode and (TeO3)2 m4 (E) bending modes. The sharp band at 3283 cm 1 assigned to the OH stretching vibration of the OH units is superimposed upon a broader spectral profile with Raman bands at 3215, 3302, 3349 and 3415 cm 1 are attributed to water stretching bands. The techniques of Raman and infrared spectroscopy are excellent for the study of tellurite minerals.Item A SEM, EDS and vibrational spectroscopic study of the clay mineral fraipontite.(2015) Theiss, Frederick L.; López, Andrés; Cipriano, Ricardo Augusto Scholz; Frost, Ray LeslieThe mineral fraipontite has been studied by using a combination of scanning electron microscopy with energy dispersive analysis and vibrational spectroscopy (infrared and Raman). Fraipontite is a member of the 1:1 clay minerals of the kaolinite-serpentine group. The mineral contains Zn and Cu and is of formula (Cu,Zn,Al)3(Si,Al)2O5(OH)4. Qualitative chemical analysis of fraipontite shows an aluminium silicate mineral with amounts of Cu and Zn. This kaolinite type mineral has been characterised by Raman and infrared spectroscopy; in this way aspects about the molecular structure of fraipontite clay are elucidated.Item SEM, EDX, Infrared and Raman spectroscopic characterization of the silicate mineral yuksporite.(2015) Frost, Ray Leslie; López, Andrés; Cipriano, Ricardo Augusto Scholz; Theiss, Frederick L.; Romano, Antônio WilsonThe mineral yuksporite (K,Ba)NaCa2(Si,Ti)4O11(F,OH) H2O has been studied using the combination of SEM with EDX and vibrational spectroscopic techniques of Raman and infrared spectroscopy. Scanning electron microscopy shows a single pure phase with cleavage fragment up to 1.0 mm. Chemical analysis gave Si, Al, K, Na and Ti as the as major elements with small amounts of Mn, Ca, Fe and REE. Raman bands are observed at 808, 871, 930, 954, 980 and 1087 cm 1 and are typical bands for a natural zeolite. Intense Raman bands are observed at 514, 643 and 668 cm 1. A very sharp band is observed at 3668 cm 1 and is attributed to the OH stretching vibration of OH units associated with Si and Ti. Raman bands resolved at 3298, 3460, 3562 and 3628 cm 1 are assigned to water stretching vibrations.