Navegando por Autor "Beganovic, Martina"
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Item 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, MartinaWe 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.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.