DSpace Repository :: Browsing by Author "Belotti, Fernanda Maria"

Browsing by Author "Belotti, Fernanda Maria"

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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, Érika
The 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..
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 Evangelista
Detailed 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.
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, Mauro
Colemanite 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.
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 Maria
Raman 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.
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, Mauro
The 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.
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, Andrés
Raman 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.
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 Maria
In 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.
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 Maria
An 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.
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 Dias
The 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.
Raman, infrared and near-infrared spectroscopic characterization of the herderite-hydroxylherderite mineral series.
(2014) Frost, Ray Leslie; Cipriano, Ricardo Augusto Scholz; López, Andrés; Xi, Yunfei; Queiroz, Camila de Siqueira; Belotti, Fernanda Maria; Cândido Filho, Mauro
Natural single-crystal specimens of the herderite–hydroxylherderite series from Brazil, with general formula CaBePO4(F,OH), were investigated by electron microprobe, Raman, infrared and near-infrared spectroscopies. The minerals occur as secondary products in granitic pegmatites. Herderite and hydroxylherderite minerals show extensive solid solution formation. The Raman spectra of hydroxylherderite are characterized by bands at around 985 and 998 cm_1, assigned to m1 symmetric stretching mode of the HOPO3_ 3 and PO3_ 4 units. Raman bands at around 1085, 1128 and 1138 cm_1 are attributed to both the HOP and PO antisymmetric stretching vibrations. The set of Raman bands observed at 563, 568, 577, 598, 616 and 633 cm_1 are assigned to the m4 out of plane bending modes of the PO4 and H2PO4 units. The OH Raman stretching vibrations of hydroxylherderite were observed ranging from 3626 cm_1 to 3609 cm_1. The infrared stretching vibrations of hydroxylherderites were observed between 3606 cm_1 and 3599 cm_1. By using a Libowitzky type function, hydrogen bond distances based upon the OH stretching bands were calculated. Characteristic NIR bands at around 6961 and 7054 cm_1 were assigned to the first overtone of the fundamental, whilst NIR bands at 10,194 and 10,329 cm_1 are assigned to the second overtone of the fundamental OH stretching vibration. Insight into the structure of the herderite–hydroxylherderite series is assessed by vibrational spectroscopy.
SEM, EDX and vibrational spectroscopic study of the phosphate mineral ushkovite MgFe2 3+(PO4)2(OH)2 8H2O – implications of the molecular structure.
(2015) López, Andrés; Cipriano, Ricardo Augusto Scholz; Frost, Ray Leslie; Belotti, Fernanda Maria
The mineral ushkovite has been analyzed using a combination of electron microscopy with EDX and vibrational spectroscopy. Chemical analysis shows the mineral contains P, Mg with very minor Fe. Thus, the formula of the studied ushkovite is Mg3 2+(PO4)2 8H2O. The Raman spectrum shows an intense band at 953 cm 1 assigned to the m1 symmetric stretching mode. In the infrared spectra complexity exists with multiple antisymmetric stretching vibrations observed, due to the reduced tetrahedral symmetry. This loss of degeneracy is also reflected in the bending modes. Strong infrared bands around 827 cm 1 are attributed to water librational modes. The Raman spectra of the hydroxyl-stretching region are complex with overlapping broad bands. Hydroxyl stretching vibrations are identified at 2881, 2998, 3107, 3203, 3284 and 3457 cm 1. The wavenumber band at 3457 cm 1 is attributed to the presence of FeOH groups. This complexity is reflected in the water HOH bending modes where a strong infrared band centered around 1653 cm 1 is found. Such a band reflects the strong hydrogen bonding of the water molecules to the phosphate anions in adjacent layers. Spectra show three distinct OH bending bands from strongly hydrogen-bonded, weakly hydrogen bonded water and non-hydrogen bonded water. Vibrational spectroscopy enhances our knowledge of the molecular structure of ushkovite.
SEM-EDX, Raman and infrared spectroscopic characterization of the phosphate mineral frondelite (Mn2+)(Fe3+)4(PO4)3(OH)5.
(2013) Frost, Ray Leslie; Xi, Yunfei; Cipriano, Ricardo Augusto Scholz; Belotti, Fernanda Maria; Beganovic, Martina
We have analyzed a frondelite mineral sample from the Cigana mine, located in the municipality of Conselheiro Pena, a well-known pegmatite in Brazil. In the Cigana pegmatite, secondary phosphates, namely eosphorite, fairfieldite, fluorapatite, frondelite, gormanite, hureaulite, lithiophilite, reddingite and vivianite are common minerals in miarolitic cavities and in massive blocks after triphylite. The chemical formula was determined as (Mn0.68, Fe0.32)(Fe3+)3,72(PO4)3.17(OH)4.99. The structure of the mineral was assessed using vibrational spectroscopy. Bands attributed to the stretching and bending modes of PO3_ 4 and HOPO3_ 3 units were identified. The observation of multiple bands supports the concept of symmetry reduction of the phosphate anion in the frondelite structure. Sharp Raman and infrared bands at 3581 cm_1 is assigned to the OH stretching vibration. Broad Raman bands at 3063, 3529 and 3365 cm_1 are attributed to water stretching vibrational modes.
Structural characterization and vibrational spectroscopy of the arsenate mineral wendwilsonite.
(2014) Frost, Ray Leslie; Cipriano, Ricardo Augusto Scholz; López, Andrés; Belotti, Fernanda Maria; Xi, Yunfei
In this paper, we have investigated on the natural wendwilsonite mineral with the formulae Ca2(Mg,Co)(AsO4)2_2(H2O). Raman spectroscopy complimented with infrared spectroscopy has been used to determine the molecular structure of the wendwilsonite arsenate mineral. A comparison is made with the roselite mineral group with formula Ca2B(AsO4)2_2H2O (where B may be Co, Fe2+, Mg, Mn, Ni, Zn). The Raman spectra of the arsenate related to tetrahedral arsenate clusters with stretching region shows strong differences between that of wendwilsonite and the roselite arsenate minerals which is attributed to the cation substitution for calcium in the structure. The Raman arsenate (AsO4)3_ stretching region shows strong differences between that of wendwilsonite and the roselite arsenate minerals which is attributed to the cation substitution for calcium in the structure. In the infrared spectra complexity exists of multiple to tetrahedral (AsO4)3_ clusters with 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 450 cm_1 are assigned to m4 bending modes. Multiple bands in the 350–300 cm_1 region assigned to m2 bending modes provide evidence of symmetry reduction of the arsenate anion. Three broad bands for wendwilsonite found at 3332, 3119 and 3001 cm_1 are assigned to OH stretching bands. By using a Libowitzky empirical equation, hydrogen bond distances of 2.65 and 2.75 Å are estimated. Vibrational spectra enable the molecular structure of the wendwilsonite mineral to be determined and whilst similarities exist in the spectral patternsb with the roselite mineral group, sufficient differences exist to be able to determine the identification of the minerals.
The application of high-temperature X-ray diffraction and infrared emission spectroscopy to the thermal decomposition of krohnkite.
(2016) Testasicca, Leonardo Pena; Frost, Ray Leslie; Ruan, Xiuxiu; Lim, Jéssica; Belotti, Fernanda Maria; Cipriano, Ricardo Augusto Scholz
High-temperature X-ray diffraction and infrared emission spectroscopy have been applied to measure the thermal stability of the sulphate mineral kro¨hnkite Na2Cu(SO4)2 2H2O. Kro¨hnkite shows a low thermal stability. The mineral decomposes into a complex mixture of sulphates below 500 C and sulphides below 650 C, before melting. Broad emission infrared bands at 3350 and 3105 cm-1 are assigned to the stretching vibration of the water units. The intensity of these two bands decreases as the temperature is raised. The intensity of these bands is lost by 250 C. The sharp IES band at 992 cm-1 is assigned to the m1 SO4 2- symmetric stretching vibration. Intensity in this band is lost by 200 C. New IES bands are noted. The important aspect of this work is the use of hightemperature X-ray diffraction to determine the thermal decomposition of a mineral, in this case krohnkite.
The molecular structure of the borate mineral szaibelyite MgBO2(OH) : a vibrational spectroscopic study.
(2015) Frost, Ray Leslie; Cipriano, Ricardo Augusto Scholz; López, Andrés; Belotti, Fernanda Maria
We have studied the borate mineral szaibelyite MgBO2(OH) using electron microscopy and vibrational spectroscopy. EDS spectra show a phase composed of Mg with minor amounts of Fe. 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 1099 cm 1 with a shoulder band at 1093 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 836 and 988 cm 1 are attributed to the antisymmetric stretching modes of tetrahedral boron. The infrared bands at 3559 and 3547 cm 1 are assigned to hydroxyl stretching vibrations. Broad infrared bands at 3269 and 3398 cm 1 are assigned to water stretching vibrations. Infrared bands at 1306, 1352, 1391, 1437 cm 1 are assigned to the antisymmetric stretching vibrations of trigonal boron. Vibrational spectroscopy enables aspects of the molecular structure of the borate mineral szaibelyite to be assessed.
The phosphate mineral sigloite Fe3+Al2(PO4)2(OH)3 7(H2O), an exception to the paragenesis rule - a vibrational spectroscopic study.
(2013) Frost, Ray Leslie; Xi, Yunfei; Cipriano, Ricardo Augusto Scholz; Belotti, Fernanda Maria; Cândido Filho, Mauro
The secondary phosphate mineral sigloite Fe3+Al2(PO4)2(OH)3_7H2O is the exception to the rule that phosphate mineral paragenesis is related to the final phase of hydrothermal mineralization at low temperatures. Sigloite was formed as an oxidation pseudomorph after paravauxite, during the last supergene paragenetic stage. We have studied the secondary phosphate mineral sigloite Fe3+Al2(PO4)2(OH)3_7H2O using vibrational spectroscopic techniques. Because the mineral is a phosphate mineral, it is readily studied by spectroscopic techniques as the phosphate and hydrogen phosphate units are readily measured. Indeed, sigloite shows the presence of both phosphate and hydrogen phosphate units in its structure. Raman bands at 1009 cm_1 with shoulders at 993 and 1039 cm_1 are assigned to stretching vibrations of PO3_ 4 and HPO2_ 4 units. The Raman band at 993 cm_1 is assigned to the m1 symmetric stretching mode of the POH units, whereas the Raman band at 1009 cm_1 is assigned to the m1 PO3_ 4 symmetric stretching mode. Raman bands observed at 506, 528, 571, 596, 619 and 659 cm_1 are attributed to the m4 out of plane bending modes of the PO4 and H2PO4 units. The Raman bands at 2988, 3118 and 3357 cm_1 are assigned to water stretching vibration. The series of bands at 3422, 3449, 3493, 3552 and 3615 cm_1 are assigned to the OH stretching vibrations of the hydroxyl units. The observation of multiple bands gives credence to the non-equivalence of the OH units in the sigloite structure.
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 Maria
Bermanite 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.
Vibrational spectroscopic characterization of the phosphate mineral hureaulite - (Mn, Fe)5(PO4)2(HPO4)2.4(H2O).
(2013) Frost, Ray Leslie; Xi, Yunfei; Cipriano, Ricardo Augusto Scholz; López, Andrés; Belotti, Fernanda Maria
This research was done on hureaulite samples from the Cigana claim, a lithium bearing pegmatite with triphylite and spodumene. The mine is located in Conselheiro Pena, east of Minas Gerais. Chemical analysis was carried out by Electron Microprobe analysis and indicated a manganese rich phase with partial substitution of iron. The calculated chemical formula of the studied sample is: (Mn3.23, Fe1.04, Ca0.19, Mg0.13)(PO4)2.7(HPO4)2.6(OH)4.78. The Raman spectrum of hureaulite is dominated by an intense Sharp band at 959 cm−1 assigned to PO stretching vibrations of HPO4 2− units. The Raman band at 989 cm−1 is assigned to the PO4 3− stretching vibration. Raman bands at 1007, 1024, 1047, and 1083 cm−1 are attributed to both the HOP and PO antisymmetric stretching vibrations of HPO4 2− and PO4 3− units. A set of Raman bands at 531, 543, 564 and 582 cm−1 are assigned to the _4 bending modes of the HPO4 2− and PO4 3− units. Raman bands observed at 414, and 455 cm−1 are attributed to the _2 HPO4 2− and PO4 3− units. The intense A series of Raman and infrared bands in the OH stretching region are assigned to water stretching vibrations. Based upon the position of these bands hydrogen bond distances are calculated. Hydrogen bond distances are short indicating very strong hydrogen bonding in the hureaulite structure. A combination of Raman and infrared spectroscopy enabled aspects of the molecular structure of the mineral hureaulite to be understood.
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 Maria
The 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.
A vibrational spectroscopic study of the anhydrous phosphate mineral sidorenkite Na3Mn(PO4)(CO3).
(2015) Frost, Ray Leslie; López, Andrés; Cipriano, Ricardo Augusto Scholz; Belotti, Fernanda Maria; Xi, Yunfei
Sidorenkite is a very rare low-temperature hydrothermal mineral, formed very late in the crystallization of hyperagpaitic pegmatites in a differentiated alkalic massif (Mt. Alluaiv, Kola Peninsula, Russia). Sidorenkite Na3Mn(PO4)(CO3) is a phosphate–carbonate of sodium and manganese. Such a formula with two oxyanions lends itself to vibrational spectroscopy. The sharp Raman band at 959 cm 1 and 1012 cm 1 are assigned to the PO43 stretching modes, whilst the Raman bands at 1044 cm 1 and 1074 cm 1 are attributed to the CO32 stretching modes. It is noted that no Raman bands at around 800 cm 1 for sidorenkite were observed. The infrared spectrum of sidorenkite shows a quite intense band at 868 cm 1 with other resolved component bands at 850 and 862 cm 1. These bands are ascribed to the CO32 out-of-plane bend (m2) bending mode. The series of Raman bands at 622, 635, 645 and 704 cm 1 are assigned to the m4 phosphate bending modes. The observation of multiple bands supports the concept of a reduction in symmetry of the carbonate anion from D3h or even C2v.

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