title: Vibrational spectroscopic study of poldervaartite CaCa[SiO3(OH)(OH)].
abstract: We have studied the mineral poldervaartite CaCa[SiO3(OH)(OH)] which forms a series with its manganese analogue olmiite CaMn[SiO3(OH)](OH) using a range of techniques including scanning electron microscopy, thermogravimetric analysis, Raman and infrared spectroscopy. Chemical analysis shows the mineral is reasonably pure and contains only calcium and manganese with low amounts of Al and F. Thermogravimetric analysis proves the mineral decomposes at 485°C with a mass loss of 7.6% compared with the theoretical mass loss of 7.7%. A strong Raman band at 852 cm(-1) is assigned to the SiO stretching vibration of the SiO3(OH) units. Two Raman bands at 914 and 953 cm(-1) are attributed to the antisymmetric vibrations. Intense prominent peaks observed at 3487, 3502, 3509, 3521 and 3547 cm(-1) are assigned to the OH stretching vibration of the SiO3(OH) units. The observation of multiple OH bands supports the concept of the non-equivalence of the OH units. Vibrational spectroscopy enables a detailed assessment of the molecular structure of poldervaartite.
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: 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
authors.affiliation: Geology Department, School of Mines, Federal University of Ouro Preto, Campus Morro do Cruzeiro, Ouro Preto, MG 35,400-00, Brazil.
authors.forename: Ricardo
authors.initials: R
authors.lastname: Scholz
authors.affiliation: Mining Engineering Department, School of Mines, Federal University of Ouro Preto, Campus Morro do Cruzeiro, Ouro Preto, MG 35,400-00, Brazil.
authors.forename: Rosa Malena Fernandes
authors.initials: RM
authors.lastname: Lima
mesh_terms: D000535:Aluminum / Q000737:chemistry; D002118:Calcium / Q000737:chemistry*; D017610:Calcium Compounds / Q000737:chemistry*; D005461:Fluorine / Q000737:chemistry; D008855:Microscopy, Electron, Scanning; D017640:Silicates / Q000737:chemistry*; D013053:Spectrophotometry; D013055:Spectrophotometry, Infrared; D013059:Spectrum Analysis, Raman; D013696:Temperature; D013818:Thermogravimetry; D014732:Vibration
chemical_list: D017610:Calcium Compounds; D017640:Silicates; C000600910:poldervaartite; D005461:Fluorine; D000535:Aluminum; D002118:Calcium
keywords: Infrared and Raman spectroscopy; Poldervaartite; Scanning electron microscopy; Silicate; Thermogravimetric analyses