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A crystal-chemical study of natural and synthetic anionic clays.

Christina de la Calle 1 Charles-Henri Pons 1 Jacques Roux 1 V. Rives 1
1 ISTO - Institut des Sciences de la Terre d'Orléans
Abstract : A comparative crystallochemical study was performed on natural and synthetic hydrotalcitelike compounds with similar compositions. The nature of the brucite-like sheet stacking was addressed by means of powder X-ray diffraction. From the resulting electron diffraction patterns it was possible to establish the order-disorder of the cations in the brucite-like sheet. The results show that a natural sample from Snarum is an intergrowth of hydrotalcite (3R1 polytype) and manasseite (2H1 polytype) at a ratio of 77:23 (wt.%). An aluminian serpentine is associated with the hydrotalcite and manasseite minerals. The structure of a synthetic sample, Mg:Al = 2:1, was determined as space group R3¯m. For a few crystals in this sample, the octahedral cation distribution is compatible with the observed supercell (a=a3). A second synthetic sample showed the presence of stacking faults and was described as a random layer sequence of two polytypes (3R and 2H).
Keywords : ANIONIC CLAYS CRYSTAL STRUCTURE HYDROTALCITE-LIKE GROUP POLYTYPE SNARUM STACKING FAULTS SYNTHETIC DOUBLE HYDROXIDES X-RAY DIFFRACTION
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https://hal-insu.archives-ouvertes.fr/hal-00069466
Contributor : Nathalie Pothier <>
Submitted on : Wednesday, May 17, 2006 - 5:33:46 PM
Last modification on : Friday, April 5, 2019 - 8:08:23 PM

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Christina de la Calle, Charles-Henri Pons, Jacques Roux, V. Rives. A crystal-chemical study of natural and synthetic anionic clays.. Clays and Clay Minerals, Clay Minerals Society, 2003, 51, pp.(2) 121-132. ⟨10.1346/CCMN.2003.0510201⟩. ⟨hal-00069466⟩

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