Micaceous Vermiculite, Glauconite, and Mixed-Layered Kaolinite-Montmorillonite Examination by Ultramicrotomy and High Resolution Electron Microscopy1
- S. Y. Lee,
- M. L. Jackson and
- J. L. Brown2
Electron optical fringes of the layer structures of micaceous vermiculite (Colorado), glauconite (Wisconsin), and mixed-lavered kaolinite-montmorillonite (Mexico) were observed after separation of clay fractions, saturation with various cations, embedment in Epoxy, thin sectioning normal to the (001) planes by a diamond-knife ultramicrotome, and high resolution, diffraction contrast electron microscopy.
In the thin section of Cs-saturated micaceous vermiculite, the electron optical fringes at 10Å may represent the basal crystallographic spacing of unweathered K mica; fringes at 11Å and 5.5Å may represent the (001) and (002) crystallographic basal orders of Cs vermiculite with the interlayers nearly closed; and fringes at 12.5Å may represent incompletely collapsed vermiculite (possibly lower layer charge and/or hydrous metal oxideinterlayered). The K-saturated glauconite particles occur as thin crystal packets consisting of 5 to 20 layers of mica + vermiculite + montmorillonite with 10Å spacing; occasional interstratified 14Å spacings are believed to represent the Raman-Jackson chlorite. A Mg-saturated, mixed-layer kaolinite-montmorillonite from Mexico showed interleaving among the electron optical (001) fringes of kaolinite (7Å), montmorillonite (12 to 14Å), micaceous vermiculite (10Å), and regularly interstratified kaolinite-montmorillonite (19Å). The mixing among the minerals in the Mexico sample appears to involve (i) a whole series of interstratifications along the Z axis, and (ii) mixing across planes defined by the X and Y axes, including regularly alternating, irregularly mixed, and zones of specific minerals.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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