Browsing by Author "Frost, Ray Leslie"
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Item An SEM, EDS and vibrational spectroscopic study of the silicate mineral meliphanite (Ca,Na)2Be[(Si,Al)2O6(F,OH)].(2015) Frost, Ray Leslie; López, Andrés; Theiss, Frederick L.; Romano, Antônio Wilson; Cipriano, Ricardo Augusto ScholzThe mineral meliphanite (Ca,Na)2Be[(Si,Al)2O6(F,OH)] is a crystalline sodium calcium beryllium silicate which has the potential to be used as piezoelectric material and for other ferroelectric applications. The mineral has been characterized by a combination of scanning electron microscopy (SEM) with energy dispersive spectroscopy (EDS) and vibrational spectroscopy. EDS analysis shows a material with high concentrations of Si and Ca and low amounts of Na, Al and F. Beryllium was not detected. Raman bands at 1016 and 1050 cm 1 are assigned to the SiO and AlOH stretching vibrations of three dimensional siloxane units. The infrared spectrum of meliphanite is very broad in comparison with the Raman spectrum. Raman bands at 472 and 510 cm 1 are assigned to OSiO bending modes. Raman spectroscopy identifies bands in the OH stretching region. Raman spectroscopy with complimentary infrared spectroscopy enables the characterization of the silicate mineral meliphanite.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 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 Assessment of the molecular structure of the borate mineral boracite Mg3B7O13Cl using vibrational spectroscopy.(2012) Frost, Ray Leslie; Xi, Yunfei; Cipriano, Ricardo Augusto ScholzBoracite is a magnesium borate mineral with formula: Mg3B7O13Cl and occurs as blue green, colorless, gray, yellow to white crystals in the orthorhombic – pyramidal crystal system. An intense Raman band at 1009 cm_1 was assigned to the BO stretching vibration of the B7O13 units. Raman bands at 1121, 1136, 1143 cm_1 are attributed to the in-plane bending vibrations of trigonal boron. Four sharp Raman bands observed at 415, 494, 621 and 671 cm_1 are simply defined as trigonal and tetrahedral borate bending modes. The Raman spectrum clearly shows intense Raman bands at 3405 and 3494 cm_1, thus indicating that some Cl anions have been replaced with OH units. The molecular structure of a natural boracite has been assessed by using vibrational spectroscopy.Item Characterization of the sulphate mineral amarantite - using infrared, Raman spectroscopy and thermogravimetry.(2013) Frost, Ray Leslie; López, Andrés; Cipriano, Ricardo Augusto Scholz; Xi, Yunfei; Silveira, Aléssio Jordan da; Lima, Rosa Malena FernandesThe mineral amarantite Fe3þ 2 (SO4)O _ 7H2O has been studied using a combination of techniques including thermogravimetry, electron probe analyses and vibrational spectroscopy. Thermal analysis shows decomposition steps at 77.63, 192.2, 550 and 641.4 _C. The Raman spectrum of amarantite is dominated by an intense band at 1017 cm_1 assigned to the SO2_ 4 m1 symmetric stretching mode. Raman bands at 1039, 1054, 1098, 1131, 1195 and 1233 cm_1 are attributed to the SO2_ 4 m3 antisymmetric stretching modes. Very intense Raman band is observed at 409 cm_1 with shoulder bands at 399, 451 and 491 cm_1 are assigned to the m2 bending modes. A series of low intensity Raman bands are found at 543, 602, 622 and 650 cm_1 are assigned to the m4 bending modes. A very sharp Raman band at 3529 cm_1 is assigned to the stretching vibration of OH units. A series of Raman bands observed at 3025, 3089, 3227, 3340, 3401 and 3480 cm_1 are assigned to water bands. Vibrational spectroscopy enables aspects of the molecular structure of the mineral amarantite to be ascertained.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.Item Chemistry, Raman and infrared spectroscopic characterization of the phosphate mineral reddingite : (MnFe)3(PO4)2(H2O,OH)3, a mineral found in lithium-bearing pegmatite.(2012) Frost, Ray Leslie; Xi, Yunfei; Cipriano, Ricardo Augusto Scholz; Belotti, Fernanda Maria; Lagoeiro, Leonardo EvangelistaDetailed investigation of an intermediate member of the reddingite–phosphoferrite series, using infrared and Raman spectroscopy, scanning electron microcopy and electron microprobe analysis, has been carried out on a homogeneous sample from a lithium-bearing pegmatite named Cigana mine, near Conselheiro Pena, Minas Gerais, Brazil. The determined formula is ðMn1:60Fe1:21Ca0:01 Mg0:01ÞP2:83ðPO4Þ2:12 ðH2O2:85F0:01ÞP2:86, indicating predominance in the reddingite member. Raman spectroscopy coupled with infrared spectroscopy supports the concept of phosphate, hydrogen phosphate and dihydrogen phosphate units in the structure of reddingite-phosphoferrite. Infrared and Raman bands attributed to water and hydroxyl stretching modes are identified. Vibrational spectroscopy adds useful information to the molecular structure of reddingite– phosphoferrite.Item Infrared and Raman spectroscopic characterisation of the sulphate mineral creedite - Ca3Al2SO4(F,OH) 2H2O - and in comparison with the alums.(2013) Frost, Ray Leslie; Xi, Yunfei; Cipriano, Ricardo Augusto Scholz; López, Andrés; Granja, AmandaThe mineral creedite is afluorinatedhydroxy hydrated sulphate of alumini um and calcium of formula Ca3Al2SO4(F,OH) _2H2O. The mineral has been studied by acombination of electron probe analysis to determine the molecular formula of the mineral and the structure assessed by vibrational spectroscopy. The spectroscopy of creedite may be compared with that of the alums. The Raman spectrum of creedite is characterised by an intense sharp band at 986 cm _1 assigned to the SO 24 _ m1 (Ag) symmetric stretching mode. Multiple bands of creedite in the antisymmetric stretching region support the concept of areduc- tion in symmetry of the sulphate anion. Multiple ban ds are also observed in the bending region with the three bands at 601, 629 and 663 cm _1 assigned to the SO 24 _ m4 (Ag) bending modes. The observation of multiple bands at 440, 457 and 483 cm _1 attributed to the SO 24 _ m2 (Bg) bending modes supports the con- cept that the symmetry of the sulphate is reduced by coordination to the water bonded to the Al 3+ in the creedite structure. The splitting of the m2, m3 and m4 modes is attributed to the reduction of symmetry of the SO 4 and it is proposed that the sulphate coordinates to water in the hydrated aluminium in bidentate chelation.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 Infrared and Raman spectroscopic characterization of the borate mineral colemanite CaB3O4(OH)3 H2O - implications for the molecular structure.(2013) Frost, Ray Leslie; Xi, Yunfei; Cipriano, Ricardo Augusto Scholz; Belotti, Fernanda Maria; Cândido Filho, MauroColemanite CaB3O4(OH)3_H2O is a secondary borate mineral formed from borax and ulexite in evaporate deposits of alkaline lacustrine sediments. The basic structure of colemanite contains endless chains of interlocking BO2(OH) triangles and BO3(OH) tetrahedrons with the calcium, water and extra hydroxide units interspersed between these chains. The Raman spectra of colemanite is characterized by an intense band at 3605 cm_1 assigned to the stretching vibration of OH units and a series of bands at 3182, 3300, 3389 and 3534 cm_1 assigned to water stretching vibrations. Infrared bands are observed in similar positions. The BO stretching vibrations of the trigonal and tetrahedral boron are characterized by Raman bands at 876, 1065 and 1084 cm_1. The OBO bending mode is defined by the Raman band at 611 cm_1. It is important to characterize the very wide range of borate minerals including colemanite because of the very wide range of applications of boron containing minerals.Item Infrared and Raman spectroscopic characterization of the borate mineral hydroboracite CaMg[B3O4(OH)3]2 3H2O – implications for the molecular structure.(2014) Frost, Ray Leslie; Cipriano, Ricardo Augusto Scholz; López, Andrés; Xi, Yunfei; Graça, Leonardo MartinsWe have studied the mineral hydroboracite CaMg[B3O4(OH)3]2 3H2O using electron microscopy and vibrational spectroscopy. Both tetrahedral and trigonal boron units are observed. The nominal resolution of the Raman spectrometer is of the order of 2 cm^-1 and as such is sufficient enough to identify separate bands for the stretching bands of the two boron isotopes. The Raman band at 1039 cm^-1 is assigned to BO stretching vibration. Raman bands at 1144, 1157, 1229, 1318 cm^-1 are attributed to the BOH in-plane bending modes. Raman bands at 825 and 925 cm^-1 are attributed to the antisymmetric stretching modes of tetrahedral boron. The sharp Raman peak at 925 cm^-1 is from the 11-B component such a mode, then it should have a smaller 10-B satellite near (1.03) x (925) = 952 cm^-1, and indeed a small peak at 955 is observed. Four sharp Raman bands observed at 3371, 3507, 3563 and 3632 cm^-1 are attributed to the stretching vibrations of hydroxyl units. The broad Raman bands at 3076, 3138, 3255, 3384 and 3551 cm^-1 are assigned to water stretching vibrations. Infrared bands at 3367, 3505, 3559 and 3631 cm^-1 are assigned to the stretching vibration of the hydroxyl units. Broad infrared bands at 3072 and 3254 cm^-1 are assigned to water stretching vibrations. Infrared bands at 1318, 1349, 1371, 1383 cm^-1 are assigned to the antisymmetric stretching vibrations of trigonal boron.Item Infrared and Raman spectroscopic characterization of the carbonate mineral huanghoite - and in comparison with selected rare earth carbonates.(2013) Frost, Ray Leslie; López, Andrés; Cipriano, Ricardo Augusto Scholz; Xi, Yunfei; Belotti, Fernanda MariaRaman spectroscopy complimented with infrared spectroscopy has been used to study the rare earth based mineral huanghoite with possible formula given as BaCe(CO3)2F and compared with the Raman spectra of a series of selected natural halogenated carbonates from different origins including bastnasite, parisite and northupite. The Raman spectrum of huanghoite displays three bands are at 1072, 1084 and 1091 cm^-1 attributed to the (CO3)^2- symmetric stretching vibration. The observation of three symmetric stretching vibrations is very unusual. The position of (CO3)^2- symmetric stretching vibration varies with mineral composition. Infrared spectroscopy of huanghoite show bands at 1319, 1382, 1422 and 1470 1091 cm^-1. No Raman bands of huanghoite were observed in these positions. Raman spectra of bastnasite, parisite and northupite show a single band at 1433, 1420 and 1554 1091 cm^-1 assigned to the m3 (CO3)^2- antisymmetric stretching mode. The observation of additional Raman bands for the m3 modes for some halogenated carbonates is significant in that it shows distortion of the carbonate anion in the mineral structure. Four Raman bands for huanghoite are observed at 687, 704, 718 and 730 1091 cm^-1 and assigned to the (CO3)^2- m2 bending modes. Raman bands are observed for huanghoite at around 627 1091 cm^-1 and are assigned to the (CO3)^2- m4 bending modes. Raman bands are observed for the carbonate m4 in phase bending modes at 722 1091 cm^-1 for bastnasite, 736 and 684 1091 cm^-1 for parisite, 714 1091 cm^-1 for northupite. Raman bands for huanghoite observed at 3259, 3484 and 3589 1091 cm^-1 are attributed to water stretching bands. Multiple bands are observed in the OH stretching region for bastnasite and parisite indicating the presence of water and OH units in their mineral structure. Vibrational spectroscopy enables new information on the structure of huanghoite to be assessed.Item Infrared and Raman spectroscopic characterization of the carbonate mineral weloganite - Sr3Na2Zr(CO3)6 3H2O and in comparison with selected carbonates.(2013) Frost, Ray Leslie; Xi, Yunfei; Cipriano, Ricardo Augusto Scholz; Belotti, Fernanda Maria; Cândido Filho, MauroThe mineral weloganite Na2Sr3Zr(CO3)6_3H2O has been studied by using vibrational spectroscopy and a comparison is made with the spectra of weloganite with other carbonate minerals. Weloganite is member of the mckelveyite group that includes donnayite-(Y) and mckelveyite-(Y). The Raman spectrum of weloganite is characterized by an intense band at 1082 cm_1 with shoulder bands at 1061 and 1073 cm_1, attributed to the CO2_ 3 symmetric stretching vibration. The observation of three symmetric stretching vibrations is very unusual. The position of CO2_ 3 symmetric stretching vibration varies with mineral composition. The Raman bands at 1350, 1371, 1385, 1417, 1526, 1546, and 1563 cm_1 are assigned to the m3 (CO3)2_ antisymmetric stretching mode. The observation of additional Raman bands for the m3 modes for weloganite is significant in that it shows distortion of the carbonate anion in the mineral structure. The Raman band observed at 870 cm_1 is assigned to the (CO3)2_ m2 bending mode. Raman bands observed for weloganite at 679, 682, 696, 728, 736, 749, and 762 cm_1 are assigned to the (CO3)2_ m4 bending modes. A comparison of the vibrational spectra is made with that of the rare earth carbonates decrespignyite, bastnasite, hydroxybastnasite, parisite, and northupite.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 Infrared and Raman spectroscopic characterization of the phosphate mineral kosnarite KZr2(PO4)3 in comparison with other pegmatitic phosphates.(2012) Frost, Ray Leslie; Xi, Yunfei; Cipriano, Ricardo Augusto Scholz; Belotti, Fernanda MariaIn this research, we have used vibrational spectroscopy to study the phosphate mineral kosnarite KZr2(PO4)3. Interest in this mineral rests with the ability of zirconium phosphates (ZP) to lock in radioactive elements. ZP have the capacity to concentrate and immobilize the actinide fraction of radioactive phases in homogeneous zirconium phosphate phases. The Raman spectrum of kosnarite is characterized by a very intense band at 1,026 cm-1 assigned to the symmetric stretching vibration of the PO4 3- m1 symmetric stretching vibration. The series of bands at 561, 595 and 638 cm-1 are assigned to the m4 out-of-plane bending modes of the PO4 3- units. The intense band at 437 cm-1 with other bands of lower wavenumber at 387, 405 and 421 cm-1 is assigned to the m2 in-plane bending modes of the PO4 3- units. The number of bands in the antisymmetric stretching region supports the concept that the symmetry of the phosphate anion in the kosnarite structure is preserved. The width of the infrared spectral profile and its complexity in contrast to the wellresolved Raman spectrum show that the pegmatitic phosphates are better studied with Raman spectroscopy.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 Infrared and Raman spectroscopic characterization of the silicate-carbonate mineral carletonite - KNa4Ca4Si8O18(CO3)4(OH,F) H2O.(2013) Frost, Ray Leslie; Xi, Yunfei; Cipriano, Ricardo Augusto Scholz; López, Andrés; Belotti, Fernanda MariaAn assessment of the molecular structure of carletonite a rare phyllosilicate mineral with general chemical formula given as KNa4Ca4Si8O18(CO3)4(OH,F).H2O has been undertaken using vibrational spectroscopy. Carletonite has a complex layered structure. Within one period of c, it contains a silicate layer of composition NaKSi8O18 H2O, a carbonate layer of composition NaCO3 0.5H2O and two carbonate layers of composition NaCa2CO3(F,OH)0.5. Raman bands are observed at 1066, 1075 and 1086 cm 1. Whether these bands are due to the CO2 3 m1 symmetric stretching mode or to an SiO stretching vibration is open to question. Multiple bands are observed in the 300–800 cm 1 spectral region, making the attribution of these bands difficult. Multiple water stretching and bending modes are observed showing that there is much variation in hydrogen bonding between water and the silicate and carbonate surfaces.Item A Raman and infrared spectroscopic analysis of the phosphate mineral wardite NaAl3(PO4)2(OH)4 .2(H2O) from Brazil.(2014) Frost, Ray Leslie; Cipriano, Ricardo Augusto Scholz; López, Andrés; Lana, Cristiano de Carvalho; Xi, YunfeiA wardite mineral sample from Lavra Da Ilha, Minas Gerais, Brazil has been examined by vibrational spectroscopy. The mineral is unusual in that it belongs to a unique symmetry class, namely the tetragonal-trapezohedral group. The structure of wardite contains layers of corner-linked –OH bridged MO6 octahedra stacked along the tetragonal C-axis in a four-layer sequence and linked by PO4 groups. Consequentially not all phosphate units are identical. Two intense Raman bands observed at 995 and 1051 cm^-1 are assigned to the m1 PO4^3- symmetric stretching mode. Intense Raman bands are observed at 605 and 618 cm^-1 with shoulders at 578 and 589 cm^-1 are assigned to the m4 out of plane bending modes of the PO4^3- . The observation of multiple bands supports the concept of non-equivalent phosphate units in the structure. Sharp infrared bands are observed at 3544 and 3611 cm^-1 are attributed to the OH stretching vibrations of the hydroxyl units. Vibrational spectroscopy enables subtle details of the molecular structure of wardite to be determined.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.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.