title: SEM, EDX and vibrational spectroscopy of the phosphate mineral vauxite from Llallagua, Bolívia.
abstract: We have undertaken a vibrational spectroscopic study of vauxite from Llallagua, Bolívia. This source is important source for rare and unusual secondary phosphate minerals and is the type locality for a number of rare phosphates such as vauxite, sigloite, metavauxite and for jeanbandyite. The chemical formula was determined as (Fe0.98 Mn0.01)∑0.99(Al2.00)(PO4)∑2.03(OH)1.98·5.95(H2O). The Raman spectrum is dominated by intense Raman bands at 978, 1000, 1009, 1027 cm(-1) assigned to the PO4(3-) and HPO4(2-) stretching modes. Low intensity Raman bands are found at 1046, 1059, 1070, 1105, 1122, 1134 and 1150 cm(-1) and are assigned to the PO4(3-) ν3 antisymmetric stretching vibrations. Raman bands of at 498, 502, 517, 523 and 535 cm(-1) are assigned to the ν4 PO4(3-) bending modes while the Raman bands at 418, 451, 461 and 470 cm(-1) are due to the ν2 PO4(3-) bending modes. The Raman spectral profile of vauxite in the hydroxyl stretching region is broad with component bands resolved at 2918, 3103, 3328, 3402, 3555 and 3648 cm(-1). Vibrational spectroscopy enables the assessment of the molecular structure of vauxite to be undertaken.
authors.affiliation: Geology Department, School of Mines, Federal University of Ouro Preto, Campus Morro do Cruzeiro, Ouro Preto, MG 35400-00, Brazil.
authors.forename: Ricardo
authors.initials: R
authors.lastname: Scholz
authors.affiliation: School of Chemistry, Physics and Mechanical Engineering, Science and Engineering Faculty, Queensland University of Technology, GPO Box 2434, Brisbane, Queensland 4001, Australia. Electronic address: r.frost@qut.edu.au.
authors.forename: Ray L
authors.initials: RL
authors.lastname: Frost
authors.affiliation: Geology Department, School of Mines, Federal University of Ouro Preto, Campus Morro do Cruzeiro, Ouro Preto, MG 35400-00, Brazil.
authors.forename: Laura
authors.initials: L
authors.lastname: Frota
authors.affiliation: Federal University of Itajubá, Campus Itabira, Itabira, MG 35903-087, Brazil.
authors.forename: Fernanda Maria
authors.initials: FM
authors.lastname: Belotti
authors.affiliation: School of Chemistry, Physics and Mechanical Engineering, Science and Engineering Faculty, Queensland University of Technology, GPO Box 2434, Brisbane, Queensland 4001, Australia.
authors.forename: Andrés
authors.initials: A
authors.lastname: López
keywords: Infrared; Llallagua; Paravauxite; Phosphate; Raman spectroscopy; Vauxite