Regularly interstratified chlorite/smectite (corrensite) occurs as grain coatings in marine and eolian sandstones of the Permian Cutler Formation in Lisbon Valley, Utah. Corrensite dominates the <2-μm clay size fraction along with lesser amounts of regularly interstratified illite/smectite in bleached, permeable sandstones that are interbedded with smectite-dominated arkosic, red, laterally discontinuous fluvial sandstones. Chemical and X-ray powder diffraction analyses of the corrensites show them to be di/dioctahedral with 060 spacings of 1.501 to 1.508 Å and to contain significantly higher Al:Mg ratios than more common trioctahedral types. Calculated structural formulae are: corrensite, M0.6(Fe3+0.2Mg1.6Al4.6)(Al0.2Si7.8)O20(OH)10; illite/smectite, M1.5(Fe3+0.1Mg1.7Al2.8)(Al1.6Si6.4)O20(OH)4; and smectite, M0.9(Fe3+0.3Mg1.2Al2.8)(Al0.6Si7.4)O20(OH)4.

Chemical similarity between the smectite and the corrensite and pervasive distribution of smectite in low-permeability shales and siltstones suggest that the smectite was a precursor of the corrensite. Three stages of mineral precipitation in the Cutler Formation have been recognized. Quartz precipitated early as grain overgrowths, followed by the formation of authigenic clay minerals, and later calcite cementation which destroyed much of the original rock fabric. Calculations show that aluminous corrensite was favored by elevated temperature (∼ 100°C), low pH, and low dissolved silica. Local hydrothermal fluids rising along the Lisbon fault apparently permeated the Cutler red bed section and precipitated the clay minerals. The assemblage corrensite + illite/smectite in the sandstones probably formed by interaction of formation fluids with smectite and an Al-bearing phase, such as K-feldspar or kaolinite.

Nine hematites and 22 goethites were synthesized by a variety of methods to obtain monomineralic samples having a range of Al substitutions and particle sizes. The second derivative of absorbance and Munsell color designations were calculated from visible reflectance spectra obtained from the dry powders. Unit-cell dimensions, Al substitution, infrared band positions, mean crystallite dimensions (MCD) from X-ray powder diffraction, and particle size from fiber-optic Doppler anemometry (FODA) were determined. Previously reported correlations between Al substitution, goethite unit-cell dimensions, and OH-stretching and -bending band positions were confirmed. For hematite, the position of the second derivative peak at ∼600 nm was negatively correlated with Al substitution (r = −.86). Munsell value and chroma were positively correlated with Al substitution (r =.94 for both), but hue was not related to Al substitution. Hue appeared to become redder, however, as particle size measured either by FODA or MCD increased. For goethite, the position of the second derivative minimum at ∼485 nm was negatively correlated with Al substitution (r = −.99). Munsell hue appeared to be related to both Al substitution and MCD perpendicular to (110), MCD110, with hues becoming redder with increasing Al substitution and yellower with increasing MCD110. Correlations between Munsell value and chroma and parameters such as Al substitution, particle size, and OH-stretching and -bending band positions were poor, but goethites synthesized by oxidation of Fe2+ solutions at room temperature had higher chromas than goethites synthesized hydrothermally from an Fe3+ system. Visually determined colors agreed well with calculated ones. Second-derivative spectra and color designations calculated from visible spectra appear to be potentially useful for quickly estimating other properties of goethite and hematite, such as Al substitution and particle size.

Intercalates of Georgia well-crystallized kaolinite with formamide, N-methylformamide (NMF), and dimethylsulfoxide (DMSO) were prepared at room temperature by dispersing the clay in the organic liquid. Several physical and chemical properties of the intercalated organic molecules and the clay, while intercalated and after de-intercalation, were examined using nuclear magnetic resonance (NMR), infrared (IR), and electron paramagnetic resonance spectroscopy (EPR), and specific heat (Cp) measurements. The chemical bonding between the inner-surface hydroxyls and the organic molecules, as indicated by IR, was strongest for DMSO and weakest for formamide. The distortion of the kaolinite layer, as shown by EPR, also was greatest for DMSO and least for formamide. NMR T1 measurements indicated a relatively strong DMSO-kaolinite surface interaction that slowed down the methyl group reorientation comparable to that in bulk solid DMSO. T1 measurements indicated a weaker interaction for NMF. De-intercalation by mild heating did not return the kaolinite to its original structural state as shown by EPR and Cp. The greatest disorder was found for the DMSO de-intercalate and the least for the formamide de-intercalate. These experiments show that for sufficiently strong bonding between the clay inner surface and the intercalating molecule, the structure of the clay is capable of distortion, which is partly temporary and partly permanent. The permanent changes probably involve the introduction of stacking faults.

The electron spin resonance (ESR) spectra and the natural and gamma-induced thermoluminescence (TL) glow curves of a series of variably cation-exchanged Fe-Ca-clays prepared from SWy-1 montmorillonite were examined. The ESR signal (g = 2) intensity associated with the surface Fe was found to increase linearly with surface Fe content up to a nominal concentration of 50% exchangeable Fe. At > 50% exchangeable Fe, no appreciable increase in the signal was noted. The TL intensity decreased linearly with increasing surface Fe up to 50% nominal exchangeable Fe. At > 50%, the signal was not appreciably further diminished. The natural TL showed only a high-temperature peak, but irradiation produced an additional low-temperature peak. One month after gamma-irradiation, the integrated TL signal was still 10–100 times higher than that from the non-irradiated material. Thus, (1) surface iron clusters may form above a certain critical Fe concentration; (2) the Fe clusters are probably less effective in quenching TL than are single Fe atoms, implying interaction between surface Fe and the stored energy content of the material; and (3) the electronic energy stored in the material as the result of gamma-irradiation is only slowly dissipated.

Published chemical data for suites of mixed-layer minerals from diagenetic sedimentary rocks, hydrothermally altered tufts, and a metasomatic bentonite bed indicate that the layer charge and composition of the different components of illite/smectite (I/S) differ from one geological environment to another. It appears that the composition of the elemental smectite and illite layers in the I/S is more or less constant for samples within each geologic setting. In the examples considered, the smectite layers are predominantly montmorillonitic in character (i.e., the charge is in the octahedral site), whereas the illite layers show different types of charge sites, depending upon the suite studied. Illite layers appear to have about the same charge in all three suites studied, slightly more than 0.7 per O10(OH)2 unit, whereas the smectite layers in the different suites range in charge from about 0.3 to 0.7 per O10(OH)2 unit. Cation-exchange capacities reflect these differences in charge, although not ideally. The differences in the composition of the component layers in each geologic suite of mixed-layer clays are probably due either to differences in the bulk chemistry of the rocks in the different suites or to differences in intensive variables, such as temperature and pressure, of the regime under which they have formed.

Titanium was introduced into the montmorillonite structure by cation exchange with polymeric Ti cations, formed by partial hydrolysis of TiCl4 in HCl. On further hydrolysis and heating, TiO2 pillars in the form of anastase were formed between the montmorillonite layers. The resulting TiO2-cross-linked montmorillonites possessed surface areas in the range 200–350 m2/g and pore volumes of about 0.2 cm3/g and were thermally and hydrothermally stable to 700°C. The basal spacing of products heated at temperatures > 200°C was about 28Å, as determined by X-ray powder diffraction and by N2-desorption pore-size analysis. The surface area increased and the pore volume decreased with increasing HCl-concentration in the Ti-solution. The uptake of TiO2 by the montmorillonite, the surface area, and the pore volume increased with increasing amount of Ti added in the preparation, to about 10 mmoles of Ti/g of montmorillonite. A further increase in the amount of Ti added resulted in a decrease in surface area, but the pore volume and the uptake of TiO2 remained almost constant. The high porosity and the interlayer spacing of the product are consistent with a structure similar to that previously proposed for smectites, cross-linked with hydroxy-Al oligocations.

Low-angle X-ray powder diffraction (XRD) measurements of soil samples, made at controlled relative humidities, showed the presence of major reflections at 20–33, 10–27, and 7–8 Å. The first reflection, which increased in intensity but did not shift in spacing with decreasing relative humidity, represents curved smectite layers. This spacing was also observed by high-resolution transmission electron microscopy. The value of 10–27 Å for the second reflection, the 001 reflection of smetite, is unusually high, probably due to poorly stacked, irregularly curved layers. The 7–8-Å reflection originates from kaolinite or dehydrated halloysite, which also contain curved layers. The more curved the layer structure of the smectite, the more difficult it is to detect this phase; therefore the XRD relative peak heights are not directly proportional to the percentages of the smectite.

The effect of heating on montmorillonites containing exchangeable Na and K has been studied by X-ray photoelectron spectroscopy (XPS). The surface composition of the unheated montmorillonite was consistent with the bulk composition, but after the sample recrystallized at 1100°C, the surface abundance of Na increased, whereas that of K decreased. Because Na and K were not present in the high-temperature crystalline products, this behavior suggests that a noncrystalline material separated from the crystalline products. The Na 1s binding energy and KL23L23 Auger kinetic energy of montmorillonite were comparable with those of Na in typically ionic compound, such as NaCl. These electron energies became smaller and larger, respectively, on heating and approached those of feldspar (albite). The K 2p3/2 binding energy of montmorillonite increased slightly on heating. The K 2p3/2 binding energy of heated sample of montmorillonite was also comparable with that of feldspar (orthoclase). These results suggest that Na and K were incorporated into feldspar-like noncrystalline materials.

Batch cation-exchange experiments were performed on chlorite, using synthetic ground water containing cesium in the concentration range 10−9–10−3 M. The sorption behavior was complex; with increasing Cs concentration, the distribution ratio of Cs decreased at first, but passed through a pronounced maximum at high Cs loadings. The desorption data differed from the sorption data only by a shift towards larger distribution ratios in the region of the maximum. The distribution ratios for isotope exchange were even larger, but varied less with Cs loadings. Similar results were obtained for KCl-treated chlorite; however, grinding or acid-treatment of the chlorite considerably altered its behavior, the absence of the maximum being the most striking change. Most of the effects at higher Cs loadings can be explained by postulating structural changes induced by the sorption of Cs.