Vibrational spectroscopic characterization of the phosphate mineral ludlamite (Fe,Mn,Mg)₃(PO₄)₂⋅4H₂O - a mineral found in lithium bearing pegmatites

A vibrational spectroscopic study of the phosphate mineral rimkorolgite (Mg,Mn2+)5(Ba, Sr)(PO4)4·8H2O from Kovdor massif, Kola Peninsula, Russia

We have studied aspect of the molecular structure of the phosphate mineral rimkorolgite from Zheleznyi iron mine, Kovdor massif, Kola Peninsula, Russia, using SEM with EDX and vibrational spectroscopy. Qualitative chemical analysis shows a homogeneous phase, composed by P, Mg, Ba, Mn and Ca. Small amounts of Si were also observed. An intense Raman peak at 975 cm(-1) is assigned to the PO4(3-) ν1 symmetric stretching mode. The Raman band at 964 cm(-1) is attributed to the HPO4(2-) ν1 symmetric stretching vibration. Raman bands observed at 1016, 1035, 1052, 1073, 1105 and 1135 cm(-1) are attributed to the ν3 antisymmetric stretching vibrations of the HPO4(2-) and PO4(3-) units. Complexity in the spectra of the phosphate bending region is observed. The broad Raman band at 3272 cm(-1) is assigned to the water stretching vibration. Vibrational spectroscopy enables aspects on the molecular structure of rimkorolgite to be undertaken.

The molecular structure of the phosphate mineral beraunite Fe(2+)Fe5(3+)(PO4)4(OH)5⋅4H2O--a vibrational spectroscopic study

The mineral beraunite from Boca Rica pegmatite in Minas Gerais with theoretical formula Fe(2+)Fe5(3+)(PO4)4(OH)5⋅4H2O has been studied using a combination of electron microscopy with EDX and vibrational spectroscopic techniques. Raman spectroscopy identifies an intense band at 990 cm(-1) and 1011 cm(-1). These bands are attributed to the PO4(3)(-) ν1 symmetric stretching mode. The ν3 antisymmetric stretching modes are observed by a large number of Raman bands. The Raman bands at 1034, 1051, 1058, 1069 and 1084 together with the Raman bands at 1098, 1116, 1133, 1155 and 1174 cm(-1) are assigned to the ν3 antisymmetric stretching vibrations of PO4(3-) and the HOPO3(2-) units. The observation of these multiple Raman bands in the symmetric and antisymmetric stretching region gives credence to the concept that both phosphate and hydrogen phosphate units exist in the structure of beraunite. The series of Raman bands at 567, 582, 601, 644, 661, 673, and 687 cm(-1) are assigned to the PO4(3-) ν2 bending modes. The series of Raman bands at 437, 468, 478, 491, 503 cm(-1) are attributed to the PO4(3-) and HOPO3(2-) ν4 bending modes. No Raman bands of beraunite which could be attributed to the hydroxyl stretching unit were observed. Infrared bands at 3511 and 3359 cm(-1) are ascribed to the OH stretching vibration of the OH units. Very broad bands at 3022 and 3299 cm(-1) are attributed to the OH stretching vibrations of water. Vibrational spectroscopy offers insights into the molecular structure of the phosphate mineral beraunite.

A vibrational spectroscopic study of the phosphate mineral whiteite CaMn(++)Mg2Al2(PO4)4(OH)2·8(H2O)

Vibrational spectroscopy enables subtle details of the molecular structure of whiteite to be determined. Single crystals of a pure phase from a Brazilian pegmatite were used. The infrared and Raman spectroscopy were applied to compare the molecular structure of whiteite with that of other phosphate minerals. The Raman spectrum of whiteite shows an intense band at 972 cm(-1) assigned to the ν1PO4(3-) symmetric stretching vibrations. The low intensity Raman bands at 1076 and 1173 cm(-1) are assigned to the ν3PO4(3-) antisymmetric stretching modes. The Raman bands at 1266, 1334 and 1368 cm(-1) are assigned to AlOH deformation modes. The infrared band at 967 cm(-1) is ascribed to the PO4(3-)ν1 symmetric stretching vibrational mode. The infrared bands at 1024, 1072, 1089 and 1126 cm(-1) are attributed to the PO4(3-)ν3 antisymmetric stretching vibrations. Raman bands at 553, 571 and 586 cm(-1) are assigned to the ν4 out of plane bending modes of the PO4(3-) unit. Raman bands at 432, 457, 479 and 500 cm(-1) are attributed to the ν2 PO4 and H2PO4 bending modes. In the 2600 to 3800 cm(-1) spectral range, Raman bands for whiteite are found 3426, 3496 and 3552 cm(-1) are assigned to AlOH stretching vibrations. Broad infrared bands are also found at 3186 cm(-1). Raman bands at 2939 and 3220 cm(-1) are assigned to water stretching vibrations. Raman spectroscopy complimented with infrared spectroscopy has enabled aspects of the structure of whiteite to be ascertained and compared with that of other phosphate minerals.

A vibrational spectroscopic study of the phosphate mineral minyulite KAl2(OH,F)(PO4)2⋅4(H2O) and in comparison with wardite

Vibrational spectroscopy enables subtle details of the molecular structure of minyulite KAl2(OH,F)(PO4)2⋅4(H2O). Single crystals of a pure phase from a Brazilian pegmatite were used. Minyulite belongs to the orthorhombic crystal system. This indicates that it has three axes of unequal length, yet all are perpendicular to each other. The infrared and Raman spectroscopy were applied to compare the structure of minyulite with wardite. The reason for the comparison is that both are Al containing phosphate minerals. The Raman spectrum of minyulite shows an intense band at 1012 cm(-1) assigned to the ν1PO4(3-) symmetric stretching vibrations. A series of low intensity Raman bands at 1047, 1077, 1091 and 1105 cm(-1) are assigned to the ν3PO4(3-) antisymmetric stretching modes. The Raman bands at 1136, 1155, 1176 and 1190 cm(-1) are assigned to AlOH deformation modes. The infrared band at 1014 cm(-1) is ascribed to the PO4(3-) ν1 symmetric stretching vibrational mode. The infrared bands at 1049, 1071, 1091 and 1123 cm(-1) are attributed to the PO4(3-) ν3 antisymmetric stretching vibrations. The infrared bands at 1123, 1146 and 1157 cm(-1) are attributed to AlOH deformation modes. Raman bands at 575, 592, 606 and 628 cm(-1) are assigned to the ν4 out of plane bending modes of the PO4(3-) unit. In the 2600-3800 cm(-1) spectral range, Raman bands for minyulite are found at 3661, 3669 and 3692 cm(-1) are assigned to AlOH/AlF stretching vibrations. Broad infrared bands are also found at 2904, 3105, 3307, 3453 and 3523 cm(-1). Raman bands at 3225, 3324 cm(-1) are assigned to water stretching vibrations. A comparison is made with the vibrational spectra of wardite. Raman spectroscopy complimented with infrared spectroscopy has enabled aspects of the structure of minyulite to be ascertained and compared with that of other phosphate minerals.

A study of the phosphate mineral kapundaite NaCa(Fe3+)4(PO4)4(OH)3⋅5(H2O) using SEM/EDX and vibrational spectroscopic methods

Vibrational spectroscopy enables subtle details of the molecular structure of kapundaite to be determined. Single crystals of a pure phase from a Brazilian pegmatite were used. Kapundaite is the Fe(3+) member of the wardite group. The infrared and Raman spectroscopy were applied to compare the structure of kapundaite with wardite. The Raman spectrum of kapundaite in the 800-1400 cm(-1) spectral range shows two intense bands at 1089 and 1114 cm(-1) assigned to the ν1PO4(3-) symmetric stretching vibrations. The observation of two bands provides evidence for the non-equivalence of the phosphate units in the kapundaite structure. The infrared spectrum of kapundaite in the 500-1300 cm(-1) shows much greater complexity than the Raman spectrum. Strong infrared bands are found at 966, 1003 and 1036 cm(-1) and are attributed to the ν1PO4(3-) symmetric stretching mode and ν3PO4(3-) antisymmetric stretching mode. Raman bands in the ν4 out of plane bending modes of the PO4(3-) unit support the concept of non-equivalent phosphate units in the kapundaite structure. In the 2600-3800 cm(-1) spectral range, Raman bands for kapundaite are found at 2905, 3151, 3311, 3449 and 3530 cm(-1). These bands are broad and are assigned to OH stretching vibrations. Broad infrared bands are also found at 2904, 3105, 3307, 3453 and 3523 cm(-1) and are attributed to water. Raman spectroscopy complimented with infrared spectroscopy has enabled aspects of the structure of kapundaite to be ascertained and compared with that of other phosphate minerals.