Clays and Clay Minerals

, Volume 41, Issue 3, pp 280–287 | Cite as

Nature of the Illitic Phase Associated with Randomly Interstratified Smectite/Illite in Soils

  • D. A. Laird
  • E. A. Nater


A dispersion-centrifugation-decantation procedure was used to isolate various particle size fractions from a sample of clay (<2 µm fraction) separated by sedimentation from the Ap horizon of a Webster soil (fine-loamy, mixed, mesic Typic Haplaquoll). The 0.02–0.06 µm size fraction was found to be enriched in an illitic phase associated with randomly interstratified smectite/illite. X-ray powder diffraction, chemical analysis, and high-resolution transmission electron microscopy confirmed that most of the illitic material in the 0.02–0.06 µm size fraction was composed of two-layer elementary illite particles with a layer charge of −0.47 per formula unit. The results demonstrate that this low-charge illitic phase can be physically separated from soil materials and that the low-charge illitic phase has chemical, morphological, and mineralogical properties that are uniquely different from those of smectite and illite.

Key Words

Chemical analysis Elementary particle High-resolution transmission electron microscopy Illite Interstratified Smectite Smectite/illite 


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Copyright information

© The Clay Minerals Society 1993

Authors and Affiliations

  • D. A. Laird
    • 1
  • E. A. Nater
    • 2
  1. 1.National Soil Tilth LaboratoryUSDA-ARSAmesUSA
  2. 2.Department of Soil ScienceUniversity of MinnesotaSt. PaulUSA

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