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A Raman spectroscopic study of copiapites Fe 2+ Fe 3+ (SO 4 ) 6 (OH) 2 · 20H 2 O: environmental implications
Author(s) -
Frost Ray L.
Publication year - 2011
Publication title -
journal of raman spectroscopy
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.748
H-Index - 110
eISSN - 1097-4555
pISSN - 0377-0486
DOI - 10.1002/jrs.2795
Subject(s) - raman spectroscopy , chemistry , pyrite , mineral , analytical chemistry (journal) , sulfate , crystallography , zinc , inorganic chemistry , mineralogy , physics , organic chemistry , chromatography , optics
Raman spectroscopy has been used to study selected mineral samples of the copiapite group. Copiapite (Fe 2+ Fe 3+ (SO 4 ) 6 (OH) 2 · 20H 2 O) is a secondary mineral formed through the oxidation of pyrite. Minerals of the copiapite group have the general formula AFe 4 (SO 4 ) 6 (OH) 2 · 20H 2 O, where A has a + 2 charge and can be either magnesium, iron, copper, calcium and/or zinc. The formula can also be B 2/3 Fe 4 (SO 4 ) 6 (OH) 2 · 20H 2 O, where B has a + 3 charge and may be either aluminium or iron. For each mineral, two Raman bands are observed at around 992 and 1029 cm −1 , assigned to the (SO 4 ) 2− ν 1 symmetric stretching mode. The observation of two bands provides evidence for the existence of two non‐equivalent sulfate anions in the mineral structure. Three Raman bands at 1112, 1142 and 1161 cm −1 are observed in the Raman spectrum of copiapites, indicating a reduction of symmetry of the sulfate anion in the copiapite structure. This reduction in symmetry is supported by multiple bands in the ν 2 and ν 4 (SO 4 ) 2− spectral regions. Copyright © 2010 John Wiley & Sons, Ltd.