Clays and Clay Minerals

, Volume 3, Issue 1, pp 146–173 | Cite as

Effect of Exchangeable Cation on X-Ray Diffraction Patterns and Thermal Behavior of a Montmoril-Lonite Clay

  • Richard C. Mielenz
  • N. Cyril Schieltz
  • Myrle E. King


A stratum of bentonite in the North Park (?) formation near Granby, Colorado, is composed largely of a dioctahedral Ca-rnontmorillonite whose formula is calculated to be
$$\left( {A{l_{2.84}}F{e_{0.50}}M{g_{0.72}}M{n_{0.04}}} \right)\left( {\mathop {A{l_{0.40}}S{i_{7.60}}}\limits^{\mathop \uparrow \limits^{{X_{0.86}}} } } \right){O_{20}}{\left( {OH} \right)_4}.$$
Na+, K+, Li+, H+, NH4+, Ca++, and Mg++ modifications were stored at 52 percent relative humidity and at 105° C-110° C. Results of X-ray diffraction, differential thermal, and thermal balance analysis depend upon the exchangeable cation and prior treatment. As with many montmorillonoids, d(001) = 22.7−30.1 Å under room conditions; ao = 5.20 Å and b0= 9.00 Å. The (001 ) interference indicates that the unit cell typically includes two packets, or possibly more, which may be derived geometrically from each other by a glide of 1.73 Å along (110) and 180° rotation. Weight loss above 190° C-3670 C exceeds that indicated by the Hofmann structure but conforms reasonably with loss indicated by a structure after that proposed by Edelman. Inverted Si-O tetrahedra are presumed to equal the number of univalent cations

It is suggested that the exchangeable cations form hydroxides during thermal analysis by reaction with (OH) at the apex of inverted Si-0 tetrahedra. The resulting H2O and NH4OH are lost during thermal analysis, thus explaining excessive weight loss. Ca (OH)2 and Mg(OH)2 so produced release one mole of H2O during thermal analysis. KOH, NaOH, and LiOH are not decomposed below 1,000° C.

Thermal products vary with exchangeable cation and crystallinity increases with prior drying. The Li+ and Ca++ modifications produce beta-quartz and alpha-cristobalite with spinel and glass, whereas the other modifications produce only spinel and glass.


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. Barshad, Isaac (1950) The effect of the interlay er cations on the expansion of the mica type of crystal lattice: Am. Mineral., vol. 35, pp. 225–238.Google Scholar
  2. Cornet, I. (1943) Sorption of NHS on montmorillonite clay: Jour. Chem. Physics, vol. 11, pp. 217–226.CrossRefGoogle Scholar
  3. Edelman, C. H. (1947) Relation entre les propriétés et la structure de quelques minéraux argileux: Verre et Silicates, vol. 12, pp. 3–6.Google Scholar
  4. Edelman, C. H., and Favajee, J. C. L. (1940) On the crystal structure of montmorillonite and halloysite: Zeitschr. Krist., vol. 102A, pp. 417–431.Google Scholar
  5. Glasstone, Samuel (1946) Textbook of physical chemistry: D. van Nostrand Co., New York, N.Y., Second Edition, 1320 pp.Google Scholar
  6. Grim, R. E., Bradley, W. F., and Brown, G. (1951) The mica clay minerals. Chapter V of X-ray identification and crystal structures of clay minerals, edited by G. W. Brindley: The Mineralogical Soc., London, England, pp. 138–172.Google Scholar
  7. Hofmann, Ulrich; Endell, Kurd; and Wilm, Diederich (1933) Krisiallstruktur und quellung von montmorillonit: Zeitschr. Krist.,vol. 86 A, pp. 340–347.Google Scholar
  8. Hofmann, Ulrich; Endell, Kurd; and Wilm, Diederich (1934) Röntg enographische und kolloidschemische Untersuchungen über Ton: Zeitschr. Angew. Chemie, vol. 47, pp. 539–547.CrossRefGoogle Scholar
  9. Lipson, H., and Cochran, W. (1953) The crystalline state, Vol. III, The determination of crystal structures: G. Bell and Sons, Ltd., London, England, 345 pp.Google Scholar
  10. MacEwan, D. M. C. (1951) The montmorillonite minerals (montmorillonoids), Chapter IV of X-ray identification and crystal structures of clay minerals, edited by G. W. Brindley: The Mineralogical Soc, London, England, pp. 86–137.Google Scholar
  11. McConnell, Duncan (1950) The crystal chemistry of montmorillonite: Am. Mineral., vol. 35, pp. 166–172.Google Scholar
  12. McConnell, Duncan (1951) The crystal chemistry of montmorillonite: Clay Minerals Bull, vol. 1, pp. 179–188.CrossRefGoogle Scholar
  13. Mielenz, R. C., Schieltz, N. C, and King, M. E. (1954) Thermo gravimetric analysis of clay and clay-like minerals: Second National Clay Minerals Conference, Proc., pp. 285–314.Google Scholar
  14. Richards, L. A. (1954) Diagnosis and improvement of saline and alkali soils: U.S. Department of Agriculture, Agriculture Handbook No. 60, 160 pp.CrossRefGoogle Scholar
  15. Smith, J. V. (1954) A revietv of the Al-O and Si-O distances: Acta Cryst., vol. 7, pp. 479–481.CrossRefGoogle Scholar
  16. Winkler, H. G. F. (1943) Kristallstruktur von montmorillonite: Zeitschr. Krist, vol. 105A, pp. 291–303.Google Scholar

Copyright information

© The Clay Minerals Society 1954

Authors and Affiliations

  • Richard C. Mielenz
    • 1
  • N. Cyril Schieltz
    • 1
  • Myrle E. King
    • 1
  1. 1.Petrographic LaboratoryU.S. Bureau of ReclamationUSA

Personalised recommendations