Mineralogical Analysis of Soil Clays Involving Vermiculite-Chlorite-Kaolinite Differentiation

Abstract

The content of kaolinite plus halloysite is differentiated quantitatively frorn chlorite by differential dissolution, even in those samples wlierein each mineral has 50OoC heat instability of the 7 a peak. Thib differentiation is possible because the structures of kaolinite and halloysite are destroyed on loss of the 7 A peak, producing amorphous material which is rapidly soluble in 0.5 N NaOH, whereas the chlorite structure remains largely intact with only partial dehydration of the octahedral layer. The amorphous residue of lcaolinite-halloysite is dissolved from the other mineral components of the heated sample with sodium hydroxide and the dissolved silica and alumina &re allocated to kaolinite. The percentages of kaolinite thus obtained for Elliott, B3-C horizon, 2-0.2 p. fraction, are 3.8 and 3.7 based on silica and alumina, respectively. Similarly, the percentages of kaolinite obtained for Buchanan, B1 horizon, 2-0.

Formation of Hydroxy-Al and -Fe Interlayers in Montmorillonite and Vermiculite: Influence of Particle Size and Temperature

“…The 2-0.2/x and 50-2 ~ size fractions were obtained by the wet sieve method in conjunction with centrifugation (Jackson, 1956). The selected samples were subjected to appropriate treatments in order to remove interlayer K (Carstea, 1965), "free iron" (Jackson, 1956) and amorphous, hydroxy interlayer and kaolinite components (Dixon and Jackson, 1960).…”

“…The chlorite-like intergrade minerals in soils have originated from montmorillonite (Singleton, 1966;Tamura, 1957Tamura, , 1958Dixon and Jackson, 1960), chlorite (Droste, 1956), beidellite (Singleton, 1966) or vermiculite (Brown, 1953;Sawhney, 1960;Dixon and Jackson, 1962). Their preferential formation in one or the other mineral matrix would depend primarily upon the intensity and duration of the weathering forces, mineralogical nature of the parent material, acidity of the medium and chemical environment.…”

Influence of Citric and Tannic Acids on Hydroxy-Al Interlayering in Montmorillonite

“…Aluminum interlayering of expandable 2:1 clay minerals is a well-known natural process (Pearson and Ensminger, 1949;Sawhney, 1958;Dixon and Jackson, 1960;Rich, 1968) and has been successfully reproduced in laboratory studies (Shen and Rich, 1962;Turner and Brydon, 1965;Violante and Violante, 1978). The formation of Al-interlayered clay is accompanied by changes in many properties of the original clay minerals, such as a reduction in the cation-exchange capacity (CEC) (Jackson, 1963;Rich, 1968;Hsu, 1968), the development ofpH-dependent layer charge (de Villiers and Jackson, 1967), the appearance ofa titratable third-buffer-range acidity (Schwertmann and Jackson, 1963), stable 14-~ X-ray powder diffraction spacings, modification to the retention and movement of certain anions, and changes in the physical and engineering properties of the clays (Barnhisel, 1977).…”

Sudoite in some Visean (Lower Carboniferous) K-bentonites from Belgium

“…Total Si, quartz content (Dixon & Jackson, 1960), and loss-on-ignition were determined by gravimetry. Ferrous and ferric iron were determined by potentiometry using the method of Ungethtim (1965).…”