Abstract: Analyses were made of 12 clay fractions and one silt fraction taken from 10 different soil horizons and clay deposits. The analyses presented were selected to represent a wide variety of analytical problems with materials containing 2:1 layer silicates, 2:2 (chlorite) layer silicates, varying amounts of 1:1 layer silicates, and in some cases with appreciable amounts of quartz, feldspars, gibbsite, hematite, magnetite, and (or) anatase.
The analyses were performed by x-ray diffraction, specific surface, integral heating weight loss, and elemental analyses. The x-ray diffraction analyses included both wedge-powder (film recorded) and oriented (Geiger counter recorded) techniques. Vermiculites of soils were found to vary in the degree to which K-saturation would close the interlayer space, but vermiculite is established by: (a) a 14 A spacing when solvated (even with glycerol); (b) closure of the interlayer spacing on heating to 500°C; and (c) an interlayer surface of about 800 m2 per gm. In the absence of adequate criteria, vermiculites can be mistakenly identified as chlorites.
The data obtained from the various techniques were combined by a system of allocation so that the minerals reported represented a unique fit of all the data. The specific surface measurement, including the measurement of interlayer surface, is a key criterion in the allocation. Interstratified (“mixed layer”) layer silicates are determined as the individual component minerals.
The beidellite of Iron River and Putnam soil clay finer than 0.08 microns is extensively interstratified with chlorite, mica, and vermiculite. No discrete x-ray crystalline zones of any of the latter three minerals were observed, but a 19.6 to 19.2 A spacing may be indicative of a superlattice of these materials and beidellite with mica and chlorite at the electron density nodes. A titaniferous ceramic clay contains 43 percent mica (as determined by allocating the 5.03 percent K2O to muscovite), 20 percent kaolinite (water loss in 300–525°C range), 21 percent TiO2 and 17 percent of other constituents (by elemental and surface analysis). This occurrence of the full complement of K2O in clay micas (both biotite and muscovite type) is general for the various clays examined, when the interlayer surface is calculated to halloysite, vermiculite, and montmorin. A general occurrence of interstratification of layer silicates is proposed.