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Authors Atanasova, M. T. ; Vyalikh, A. ; Scheler, U. ; Focke, W. W.
Title Characterization of rectorite from the Beatrix Gold Mine in South Africa
Date 01.06.2016
Number 45491
Abstract Three rectorite samples from the Beatrix Gold Mine, South Africa were characterized. Scanning electron microscopy revealed a layered morphology. High resolution transmission microscopy showed well distinguished light and dark layers of about 2.20 nm consistent with the 1:1 interstratified mica-smectite nature. X-ray diffraction measurements confirmed the basal spacing d001 of 2.20 nm consistent with a one-water-layer structure. Unit cell parameters, for a monoclinic unit cell with primitive lattice, refined to a = 5.177 Å; b = 8.980 Å; c = 22.489 Å and ß = 97.335° with mean crystallite size around 14 nm and calculated cell volume of 1045 Å3. The Greene-Kelly test suggested that the expandable smectite layers have montmorillonite-beidellite composition. Nuclear magnetic resonance spectroscopy indicated a high degree of Al substitution and the presence of two different Al sites corresponding to six- and four-fold octahedral and tetrahedral aluminum respectively. The chemical composition and diffraction data suggest that the mica is Na-Ca-rich, i.e. of paragonite-margarite series. The fixed interlayer regions (mica interlayers) contains proportionally dominant Na+ and Ca2 + and minor amounts of K+. The exchangeable smectitic interlayers contain almost equal amounts of Na+ and Ca2 + ions. The distribution of the interlayer Na+ ions was quantified by 23Na solid-state NMR spectroscopy. It points to a three component mixed-layer structure with considerable variation in the composition of the mica layer of the different samples.
Publisher Applied Clay Science
Wikidata
Citation Applied Clay Science 126 (2016) 7-16
DOI https://doi.org/10.1016/j.clay.2016.02.028
Tags rectorite mixed-layer interstratification xrd sem solid-state nmr thermal analysis ftir

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