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Iron-bearing smectites: a revised relationship between structural Fe, b cell edge lengths and refractive indices

Published online by Cambridge University Press:  09 July 2018

M. Heuser*
Affiliation:
Clay and Interface Mineralogy, RWTH Aachen University, Bunsenstrasse 8, D-52072 Aachen, Germany
P. Andrieux
Affiliation:
Université de Poitiers, CNRS UMR 7285 IC2MP, HydrASA, 6 rue Michel Brunet, F-86022 Poitiers Cedex, France
S. Petit
Affiliation:
Université de Poitiers, CNRS UMR 7285 IC2MP, HydrASA, 6 rue Michel Brunet, F-86022 Poitiers Cedex, France
H. Stanjek
Affiliation:
Clay and Interface Mineralogy, RWTH Aachen University, Bunsenstrasse 8, D-52072 Aachen, Germany

Abstract

Structural iron in smectites correlates with the cell edge length b and increases the refractive index. The cell edge length b is usually obtained from the position of the (060) reflection, but in this work we show that such b values differ from the values obtained from Rietveld fits because contributions from (hkl) reflections shift the position of the (060) reflection. The correlation between Fe and cell edge length b was significant (r2 > 0.99); the relationship is b [Å] = 8.9977(0.0035) + 0.1117(0.0032) × Fetot. Furthermore, we present for the first time measurements of the refractive index n of Fe-bearing smectites, applying a recently published turbidity method (Weidler & Friedrich, 2007). The refractive index correlates both with structural iron (r2 = 0.64) and with b (r2 = 0.94).

Type
Research Article
Copyright
Copyright © The Mineralogical Society of Great Britain and Ireland 2013

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