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This article in SSSAJ

  1. Vol. 33 No. 5, p. 684-690
    Received: Nov 25, 1968
    Accepted: June 9, 1969

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Ion Selectivity of Micas as Influenced by Degree of Potassium Depletion1

  1. J. Le Roux and
  2. C. I. Rich2,3



The Rb/Sr selectivity coefficient of muscovite and biotite reached a maximum at an intermediate degree of K-depletion of these micas. The Rb/Sr ratio of ions absorbed from a solution, initially containing equivalent amounts of Rb and Sr, was determined for the two micas altered to different degrees to Mg-vermiculite. X-ray diffraction of the Rb-Sr treated vermiculites gave nonintegral peaks for the basal reflections, indicating random interstratification of Rb and Sr + Mg saturated layers. The results support previous proposals that selective sites for K are probably situated at wedge-shaped zones occurring at frayed edges and deeper within the altered mica particles. As K is removed from mica, the number of such wedges should first increase and then decrease. Selectivity of K and other large monovalent ions should also follow this same trend.

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