Zeta-potentials of Na- and Ca-bentonites treated with varying amounts of Ca(OH)2 were measured by a Northrop-Kunitz horizontal cell and non-polarizing Zn-ZnSO4 electrodes. Influences of other factors such as particle size, clay concentration, and salt concentrations were also studied.

The results indicate a four-stage change in zeta-potential and viscosity when Ca(OH)2 is added in increasing amounts to Na-bentonite suspensions

In the first stage, the addition of small amounts of lime caused no change in zeta-potential suggesting a counteracting effect of Ca++ adsorbtion and reaction of OH-ions to increase the negative surface charge with only a slight change in viscosity. In the second stage, the addition of more lime resulted in a rapid decrease in zeta-potential accompanied by a rapid increase in viscosity and appearance of flocs. In the third stage, additional lime led to a slower decrease in zeta-potential but a continued rapid increase in viscosity and the formation of distinct large flocs. Apparently in all three stages the plentiful OH- ions caused dissociation of weakly acidic groups to provide additional negative sites for linking the clay particles by Ca++ ions. The dissociation of weakly acidic groups probably reached its full capacity by the end of the third stage, termed the “lime retention point”. In the fourth stage, the additional Ca(OH)2 in excess of the lime retention point caused a slight change in zeta-potential and a slight decrease in viscosity. In this stage free lime was available for slow pozzolanic reaction.

In the Ca-bentonite-Ca(OH), system, the first stage was an increase in zeta-potential due to dominant influence of OH- potential-determining ions. The second stage was a rapid decrease in zeta-potential and increase in viscosity, corresponding to the third stage in treatment in the Na+-clay. The end of the second stage is the lime retention point, after which excess lime is used for pozzolanic reaction.

Transmission electron microscopy-energy dispersive X-ray analysis (TEM-EDX) represents an effective tool for determining the stoichiometric composition of clay minerals, but the methodology is often hampered by analytical difficulties. Studies of beam-sensitive minerals, such as smectites, are associated with low count intensities and dynamic loss of cations (e.g. K+, Na+, and Al3+), which can lead to erroneous quantifications of composition. After exploring how to minimize cation migration by reducing the beam current density to <5 pA cm–2, the most reliable and consistent compositions were determined using 1 μm2 area measurements of particles acquired in normal TEM mode where the electron beam was parallel, the degree of specimen damage was at its minimum and good acquisition intensities (>10,000 cps) were acquired. Based on 528 TEM-EDX area analyses, the composition of Wyoming montmorillonites (SWy-1, SWy-2, and SWy-3) was studied in their natural and Ca-saturated states from thin (<50 nm thick) particle aggregates lying on lacey carbon films. Overall, the TEM-EDX results confirmed the heterogeneous charge distributions of montmorillonite at the particle and sample levels. The average composition per formula unit of SWy-1 to -3 was determined as: (Na0.12Ca0.04Mg0.03K0.02)(Si3.91Al0.09)(Al1.57Mg0.27Fe0.19)2.03 O10(OH)2 · nH2O, where the tetrahedral and octahedral layer charges are –0.09 and –0.19 per O10(OH)2, respectively, and the total layer charge ranges from –0.25 to –0.30 per O10(OH)2 (mean of –0.28). This study demonstrates how TEM-EDX can provide new insight into the natural heterogeneities of smectite chemistry as long as adequate calibration and specimen damage control procedures are implemented.

The weathering and fluvial transport stages of a sedimentation sequence of the Cheyenne River in Eastern Wyoming are discussed. The river heads in east-central Wyoming, crosses several rock units in its eastward path before reaching the Angostura Reservoir in southwestern South Dakota. The drainage area of the Cheyenne River above the Angostura Reservoir comprises about 9000 square miles.

Weathering profiles of the rock units traversed by the river in this drainage area were sampled to determine their respective contributions to the sediment load. Among these formations are the lithologically diverse Chadron, Brule, Fort Union, Lance, Pierre, and Spearfish. The textural and mineralogical analyses of the weathered outcrops were compared with those of sediment samples collected at gauging stations operated by the Water Resources Division of the U.S. Geological Survey.

X-ray diffraction studies of the weathered rock profiles and of the suspended sediment indicate a diverse clay mineral assemblage in the 2-1µ diameter size fraction. Kaolinite, illite, and vermiculite occur along with quartz and feldspar. However, the <1µ size fraction of the suspended sediment contained only montmorillonite. The kaolinite content of the 2-1µ size fraction of the suspended sediment increased in the direction of flow, at the expense of vermiculite and ilIite.

The computed and observed amounts of sediment contributions by the various rock units show a fairly good fit; the data indicate the importance of defining mineral composition in terms of discrete size separates, cven under 2µ diameter. The increase in kaolinite content in the 2-1µ size fraction of the suspended sediment may be due to bank contribution downstream from the gauging stations. The montmorillonite content of the < 1µ size fraction is unchangcd by transport.

The tension phenomenon described herein occurs in a wide variety of porous materials, including sands, clays, agricultural soils and porous rocks. When some of the water is removed from a water-saturated porous system, the residual water evidently remains physically interconnected, judging from the fact that water can be transmitted through the system at reduced water content by suction.

The removal of water may result in contraction of the system, as in the case of clay, or in the entry of air, as in the case of sand. The liquid phase and the solid phase in contact with it comprise a closely linked force system. Equilibrium can be established between the system at reduced water content and a separate mass of water at reduced pressure through a porous membrane in contact with both.

The equilibrium tension required in the external water phase is considered an attribute of the moist, porous, system itself. From this point of view, the tension originates through the combined action of the internal forces of the system in a virtual displacement of water. It follows from this and from the principle of virtual work that the tension is numerically equal to the differential work done by the internal forces per unit volume of water absorbed.

The movement of water, under tension, through porous systems represents a special class of flow phenomena in which tensiometers or equivalent devices are required for measuring the hydraulic potential. Flow patterns can be determined in much the same way as in systems characterized by positive hydrostatic pressures, but special attention must be paid to the Darcy coefficient (the capillary conductivity) which varies with the tension.

The theoretical conditions for the equilibrium of water in the soil and for emergence from the soil have been developed in terms of the tension and certain applications have been indicated.

The phenomenon referred to in the soil science literature as moisture tension has been recognized for almost forty years and has been used as a means of explaining the absorption and movement of water in the soil. It is closely related to osmotic pressure but its mechanism cannot in general be identified with the traditional mechanisms of osmotic pressure. Moisture tension has been observed in wet clay soils and in other finely divided porous systems containing interstitial water, but the phenomenon is not confined to colloidal systems, since moist sand and moist porous rock, such as pumice, show similar effects.

Nodules of alunite and hydrated halloysite occur in the upper part of the Cretaceous Blue Hill shale at three localities in west-central Kansas. They have formed at the contact of septarian concretions with the shale and are associated with gypsum. The nodules are judged to have been formed by the action of sulfuric acid from pyrite on the potassium-bearing minerals of the Blue Hill shale, perhaps under special conditions of pH and Eh produced locally by the presence of septaria.

The minerals were studied and identified by x-ray diffraction, thermal data, chemical analysis, and electron and light microscopy.

The apparent porosity of flint, boehmite and diaspore clays bears no direct, consistent relation to the permeability of the same type of clay or to the alumina content of each type. The coefficient of permeability varies with the type and the structure of each flint clay. Diaspore clays have high permeability compared to flint clays, and the boehmite clays measured generally have a permeability intermediate between that of diaspore and that of flint clays. The apparent increase in permeability with increase in alumina content suggests that permeability has increased as silica was removed from flint clay to form boehmite and diaspore clays.

A vertical pipe of diaspore clay 1½ inches in diameter was collected by Fred Mertens of the Laclede Christy Company at the Shockley-Thompson diaspore pit at Belle, Missouri. The pipe contains 69.16 percent alumina compared with 55.30 percent alumina for the average of the walls a few inches from the pipe. Diaspore in the pipe has vertical banding indicating it was deposited along a vertical crack. The formation of cracks in brittle flint clay is an important process in increasing the permeability and providing openings along which ground water can migrate.

A restudy of boehmite and diaspore clays emphasizes not only a replacement of the colloform and oolitic structures of flint clays by diaspore and boehmite, a gradual alteration of flint clay to diaspore clay along fractures, and second-generation diaspore cutting early diaspore, but also the importance of secondary processes in the origin of diaspore and boehmite clays.

Crystallites of the finest fraction of a clay mineral from Rosamund, California, which account for over 50 per cent of the total weight, are identified as wairakite single crystals of 0·1–1 μ size. High-magnification electron microscopy revealed flat, almost perfectly square-shaped lamellae, which consist of superimposed layers of approximately < 50 Å thickness. Electron diffraction patterns from a selected single crystal proved that the basal plane of the crystallite aligned perpendicular to the electron beam is the (111) plane. It is suggested on the basis of the present study and the report of previous investigators that the pseudocubic wairakite crystals cleave along their (111) and ($\bar 1$11) planes. The indices of high order reflections, unpublished or previously reported as uncertain, are determined.

The mobility of rare-earth elements (REE) in low-grade diagenetic regimes, potentially leading to their clay-mediated fractionation, remains poorly understood. This study draws evidence from the argillitized Miocene tuff of the Southwestern Pannonian Basin (SPB) and adjacent Dinarides intramontane basins (DIB) to investigate the role of illite-smectite (I-S) in controlling early diagenetic REE behavior. The present research relies on detailed mineralogical, geochemical, and gas adsorption characterization of altered tuff, focusing on comparative analyses of the REE chemistry obtained by in situ laser ablation inductively coupled plasma mass spectrometry of glass shards and that of spatially related authigenic clay minerals. The depositional environment, in which the volcanic glass alteration took place, gave rise to the composition of secondary paragenesis, revealing a dominance of I-S. The normalized REE geochemistry of clay separates show similarities to unaltered glass, but notable differences indicate fluctuations in fluid/rock ratio environments. The redox conditions during glass alteration are reflected in Ce and Eu anomalies and indicate the ranges from oxic to anoxic across the analyzed tuffs. The results showed that I-S, formed through volcanic glass diagenesis, inherits magmatic REE signatures but also fractionates REE based on more reducing physiochemical conditions. The strong correlation between smectite content of I-S and a total budget of fractionated REE posits the smectite interlayers as prime factors controlling the REE fractionation during volcanic ash diagenesis. Furthermore, greater specific surface area values and development of slit-shaped porosity along the non-basal edges of I-S particles contributed to REE adsorption. These findings contribute to our understanding of REE behavior in low-temperature diagenetic environments, emphasizing the significance of clay minerals in retaining and fractionating these elements which may lead ultimately to the formation of economically viable ion-adsorption clay deposits.

Replacement of alumina by ferric iron in the lattice structure features the nontronite member of the montmorillonite group. Chromium, in significant amounts, replaces ferric iron in the lattice structure of some nontronites.

Effect of migration of clay minerals under colloidal suspension and the transfer of true solutions complicate correlations of the chemical composition. Moreover, many nontronites are secondary and occur in fracture zones associated with kaolinitic and halloysitic clay. A tendency of certain nontronites to form lathlike crystals is well known.

Chemical composition of 15 selected nontronites from the United States of America, Germany, and Russia indicate a range of 30 to 60 percent SiO2, and a range of from 25 to 40 percent Fe2O3. Minor constituents are the oxides of magnesium, titanium, ferrous iron, and calcium, and the alkalis, potassium and sodium.

Magnesium percentages found in nontronites are proportional to the value of sigma for octahedral coordination. Ferrous iron is proportional to titanium in montmorillonite, and a similar relationship is observed in the nontronites.

A deficiency in alkalis typifies the composition of montmorillonite and this condition is likewise true in most nontronites. Potassium is limited to a narrow statistical range of between 0.5 to 0.6 ions of Al in tetrahedral coordination against an extreme deficiency of ferric iron and magnesium (combined) of less than 0.05 ion in octahedral coordination. Thus calcium occurs as the principal large cation and is present in nearly all the nontronites studied.

Comparison was made between a sample of Wyoming bentonite and its synthetic analogue. Equivalent decomposition temperatures and mineral phases were obtained in hydrothermal environments and by calcinations.

In spite of the fact that the kaolinite-mullite reaction series had been the subject of extensive investigations since the work of Le Chatelier in 1887, nevertheless many-problems are still remaining. One of the major problems is the interpretation of the first exothermic peak at 980°C.

Based on sufficiently accurate thermodynamic data of kaolinite and its high temperature products, equations were derived, expressing the changes of free energy with temperature for all various possible reactions of kaolinite between 298°K and 2300°K.

The most favourable reaction at 980°C, (1253°K), is that which yields mullite and ß quartz.

The exothermic peak at 980°C is neither due to crystallization of γAl2O3 and SiO2 nor to mullite, γAl2O3 and SiO2 but most probably due to crystallization of mullite and silica. The values of ΔG1250°K are: -40,919, -88,991 and -105,022 cal/mol respectively.

The clay deposits of eastern Washington and northern Idaho are along the eastern edge of the Columbia River Plateau physiographic province. Three types of clay occur in the area: (a) residual clay derived from the Columbia River basalt of Tertiary age; (b) residual clay derived from the Cretaceous granodiorite and related intrusive rocks of the Idaho batholith; and (c) transported clay. The two types of residual clay were formed during a protracted lull in the outpouring of the Columbia River basalt, when the relief of land surface was low to moderate and the climate was warm and humid. The topography and climate during this interval were probably ideal for leaching and oxidation. The transported clay is chiefly a product of the weathered granodiorite and related intrusive rocks. Most of it accumulated in basins formed by damming of streams by basalt flows.

Kaolinite and halloysite are the principal clay minerals found in the area. The residual clay derived from basalt is chiefly composed of halloysite. Most of this clay is colored blue, gray or grayish black by finely disseminated ilmenite and locally it is stained blown by limonite; most of it has a relict basaltic texture.

The residual clay derived from granodiorite and related intrusive rocks contains both kaolinite and halloysite, and the transported clay is predominantly kaolinite. Both of these clays are white and contain abundant quartz grains and mica flakes. The residual clay has a relict granitic texture, and the transported clay has a well-developed bedding and is interbedded with elastic material.