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Identification by RAMAN Microscopy of magnesian vivianite formed from Fe2+, Mg, Mn2+ and P043-’ in a Roman camp near fort Vechten, Utrecht, The Netherlands
Published online by Cambridge University Press: 01 April 2016
Abstract
The presence of a magnesian vivianite (Fe2+)2.5(Mg,Mn,Ca)0.5(PO4)2·8H2O, has been identified in a soil sample from a Roman camp near Fort Vechten, The Netherlands, using a combination of Raman microscopy and scanning electron microscopy. An unsubstituted vivianite and baricite were characterised for comparative reasons. The split phosphate-stretching mode is recognised around 1115, 1062 and 1015 cm−1, while the corresponding bending modes are found around 591, 519, 471 and 422 cm−1. The substitution of Mg and Mn for Fe2+ in the crystal structure causes a shift towards higher wavenumbers compared to pure vivianite. As shown by the baričite sample substitution causes a broadening of the bands. The observed broadening however is larger than can be explained by substitution alone. The low intensity of the water bands, especially in the OH-stretching region between 2700 and 3700 cm−1 indicates that the magnesian vivianite is partially dehydrated, which explains the much larger broadening than the observed broadening caused by substitution of Mg and Mn in vivianite and baričite.
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- Copyright © Stichting Netherlands Journal of Geosciences 2003
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Present address: Goudse Steen 15, 3961 XS Wijk bij Duurstede, The Netherlands
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