Publication: The effect of the octahedral cations on the
dimensions of the palygorskite cell
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Publication Date
2007
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Mineralogical Society
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Abstract
High-resolution synchrotron X-ray diffraction recorded on a collection of
palygorskites with different chemical compositions (obtained by analytical electron microscopy)
permits unambiguous correlation of the crystallographic parameters a (or a sin b if a monoclinic
phase is considered) with the nature of the octahedral sheet, i.e. with both the number of octahedral
positions that are occupied and the type of octahedral cation. No significant changes in the lattice
parameters b and c are observed. The unit cell modification consists essentially of an expansion in a
as the number of cations with larger ionic radii (Mg2+ and Fe3+) predominates over smaller cations
(Al3+). A linear dependency of a (or a sin b) on the chemical composition of the octahedral sheet was
obtained that can be used for classifying palygorskite into compositional groups, using only
conventional diffraction data, without the need for chemical analyses.