title: Vibrational spectroscopy of the phosphate mineral lazulite--(Mg, Fe)Al2(PO4)2·(OH)2 found in the Minas Gerais, Brazil.
abstract: This 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 HPO4(2-) 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 ν1PO4(3-) symmetric stretching modes. The intense bands at 1035, 1054, 1081, 1118 and 1154 cm(-1) are assigned to the ν3PO4(3-) 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 ν4 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 ν2 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.
authors: School of Chemistry, Physics and Mechanical Engineering, Science and Engineering Faculty, Queensland University of Technology, GPO Box 2434, Brisbane, Queensland 4001, Australia. r.frost@qut.edu.au
authors: Ray L
authors: RL
authors: Frost
authors: Yunfei
authors: Y
authors: Xi
authors: Martina
authors: M
authors: Beganovic
authors: Fernanda Maria
authors: FM
authors: Belotti
authors: Ricardo
authors: R
authors: Scholz
mesh_terms: D001938:Brazil; D007501:Iron / Q000737:chemistry; D008274:Magnesium / Q000737:chemistry; D008903:Minerals / Q000737:chemistry*; D010710:Phosphates / Q000737:chemistry*; D013055:Spectrophotometry, Infrared; D013059:Spectrum Analysis, Raman
chemical_list: D008903:Minerals; D010710:Phosphates; D007501:Iron; D008274:Magnesium