An investigation of the behavior of clay systems in drilling fluids was begun in 1958 to determine the cause of gelation in lime-treated muds with increased temperatures incurred during drilling operations. Mud systems were evaluated by physical property measurements, cation exchange data, X-ray diffraction analysis, and electron microscopy before and after hydrothermal treatment. Selected samples were rerun after two years' storage at laboratory temperatures.

High-temperature gelation of lime-caustic muds is caused by the synthesis of calcium silicate hydrates, hereafter referred to as CSH, in general and tobermorite (XCaO, SiO2, H2O) specifically. These materials are considered the principal cementing agents of Portland cement. Spheroidal poorly crystallized tobermorite was produced from interlayered illite-montmorillonite muds. Laths and needles of crystalline tobermorite (11.3–11.6 Å type) were synthesized from the pure montmorillonite systems. Zeolite minerals were synthesized concurrently and were the dominant alteration product when Ca(OH)2 was not added to the system.

Synthesized aged (2 years) mud systems were studied after 8 weeks of dialysis with distilled water. Corundum was observed in samples where tobermorite formed, and was the dominant insoluble residue after HCl treatment. Much sharper diffraction maxima were obtained of the CSH compounds after dialysis or glycerine washing.

“Al-chlorite,” “Al-vermiculite,” and “Al-micas” were synthesized when treatments included aluminum ions. The products formed were of varying stabilities after washing with distilled water and HCl. Glycerol expanded the montmorillonite which had not reacted, but no expansion from the 10 Å or 14 Å d(001) spacing of the new product occurrred.

Clays and their composites have been widely used for secondary containment walls for underground storage tanks and landfills. The pore-size changes occurring in the clay have a profound effect on its permeability. This study presents a new method for evaluating the use of an atomic force microscope (AFM) for studying wet clay in a non-aqueous state in order to determine the pore-size of clay at various water contents, a type of study typically performed by the more expensive environmental scanning electronic microscope. The method consists of mounting a sponge saturated with water under the sample in order to prevent drying by the heat generated by the AFM electronics. The micro-scale AFM image results show that the clay-particle separations reduce linearly as the water content increases. This change in pore-size is postulated to be attributed to the reduction in the size of the diffuse double layer and more extensive hydrogen bonds between clay particles and bipolar water molecules. The AFM was not able to produce nano-scale images due to excessive adhesion between the cantilever arm and the wet clay sample.

In the intermountain states, a region deficient in kaolinite and alumina clays, there is an increasing demand for refractory clay. In this arid region residual kaolins are not developed in quantity from feldspathic intrusives. Glassy, siliceous extrusives alter commonly to mont-morillonite of the montmorillonite-beidellite series. Zeolites, principally analcime and heu-landite, often are alteration products. Under certain conditions kaolinite, halloysite, or saponite will form; several tuffaceous deposits were investigated in an attempt to determine these environmental conditions, especially the physico-chemical environment necessary to produce kaolin clay.

Zeolites are developed where the pyroclastics are deposited in an alkaline lake; saponite is formed locally in this environment as a result of hot-spring activity. On river slopes and spurs the siliceous volcanics alter to kaolinite and montmorillonite; where associated with calcareous hot-spring activity in a fresh-water lake, halloysite results. Montmorillonite-beidellite develops where these special conditions do not obtain.

The prospects of finding a residual kaolinite deposit developed from siliceous volcanics are not good. Hydrothermal alteration appears to be the only means by which a siliceous volcanic will be converted to a sizeable refractory clay deposit in this region.

Sodium-saturated montmorillonite was used to prepare aqueous suspensions of varying concentration between 0.06% and 3.0%. Compacted columns of glass beads and carborundum constituted the porous media. The system was maintained under saturated flow conditions at hydraulic gradients of 2 and 4. In order to study the relationship of clay properties to those of the porous media, the zeta potential of both suspension and media was determined. A mathematical model of the system was developed that would predict the deposition of clay at various depths in the columns, given concentration and flow rate of the suspensions. In order to test this model, a procedure was developed for tagging the clay with 46Sc, sampling the columns, and determining the amount of deposition using a single-channel gamma-ray spectrometer. Using an activity level of 0.15 microcurie per liter of a 1% suspension it was possible to detect reliably 10 mg of clay in a 40 g sample of the porous media. The results indicate two mechanisms operating in the process of removal of the clay from suspension. One of these, interstitial straining, operates at the surface of the porous media column; while the second, a combination of diffusion and gravitational settling, operates below the surface.

The results of this research have potential applications in the solution of engineering problems relating to water resources conservation such as reservoir seepage control, infiltration of sediment-laden water into the soil, and ground water recharge. Also, the results may be important for answering questions concerning pollutant movement into the water supply through porous strata. All the above are examples in which a colloidal suspension is moving into or through porous media; therefore, an improved understanding of the principles of flow of colloidal suspensions in porous media can contribute to the solution of these engineering problems.

A road log of a 37-mile field trip is presented. The route passed over a group of Early Tazewell moraines and the till plains in between. Stops were made at Flanagan, Drummer and Elliot soil profiles and the type Fithian illite locality. The soil profiles and Fithian cyclothem are described.

Discussions and recommendations of The Clay Mineral Society, Nomenclature Committee, 1965-6, are summarized.

A review of mineralogical and geochemical studies on Recent sediments indicates that the clay fraction of marine sediments is not in isotopic or chemical equilibrium with the oceanic reservoir and will not reflect the chemical environment of deposition. Consideration of the sedimentary geochemistry of the alkali metals suggests that fractionation of these elements, which may be one of the major features of the chemical evolution of ocean water, occurs in the terrestrial weathering environment during the formation of clay minerals and in the subsurface environment during clay mineral diagenesis. It is proposed that during the initial stages of oceanic development the Na/K ratio of ocean water was adjusted to a value of forty to fifty by the extensive diagenesis of the existing natural water. With an increase in oceanic volume and a major change in the hydrologic cycling of natural waters the chemical evolution of alkali metals in ocean water has now become primarily controlled by mixing with continental drainage water.

The Middle Paleozoic shales of northern Ohio contain a well-crystallized variety of illite as their main constituent. Powder diagrams relate the illite to the two-layer monoclinic muscovite crystallization. The low asymmetry of the 10 A reflection indicates that inter-layering of non-mica or hydrated-mica units is small. The relative intensities of the basal reflections show that the illites approach the ideal muscovite composition but have about one-fourth the octahedral aluminum replaced by iron and are deficient about one-half or less the interlayer potassium. The interlayer positions are essentially anhydrous. One-dimensional Fourier syntheses made before and after thermal treatment of the illites indicate that intensity changes of the basal reflections due to thermal treatment are related to electron density changes confined to the octahedral layer. Dehydroxylization begins at moderately low temperatures and continues until an anhydride structure is formed.

The purpose of this study was to investigate the structural and chemical modifications of phyllosilicates that occur under natural conditions, using the progressive deformation of chlorite (sudoite) present in quartz-rich veins from the Internal Zone of the Rif range (Morocco) as the model system. Signs of chlorite deformation include kinks, chevron-like folds, and fractures. The samples also contain later, undeformed grains, which sealed the fractures or grew with (001) perpendicular to the compressive stress. Deformation-induced structural changes consist mainly of basal cleavages associated with ordered replacement of brucite sheets by hydrated layers, thus leading to irregular microdomains of mixed-layer chlorite-vermiculite and sudoite. Such structural modifications represent a mechanism for accommodating the compressive stress. Structural changes were accompanied by minor chemical ones, which lead from di,tri-chlorite (sudoite) to phases with a more trioctahedral character (mixed-layer chlorite-vermiculite). The hydration reaction occurred throughout a topotactic replacement of the pre-existing sudoite grains. Later, undeformed grains consist of mixed-layer chlorite-vermiculite intergrown with retrogressive kaolinite and minor Fe oxide, and are interpreted as having formed through a dissolution-precipitation process, during deformation. Retrogression of sudoite probably occurred during the latest stage of exhumation, in low-temperature conditions.

Data on montmorillonite and illite collected by A. Kahn were further analyzed to show the relationship between particle geometry and the optical density (OD) of the clay suspensions. A correction was introduced to the calculations of the minor dimension of the montmorillonite particles which took into account the volume of water between unit layers.

The assumption of disc geometry which was used by A. Kahn in the calculations of the clay particle dimension was found to be consistent with his OD measurements, thus showing that optical measurements can be used to find an equivalent radius of montmorillonite and illite when the general geometry of the particles is the same.

The hydrogen isotopic composition (δ2H) of authigenic clay minerals has been used extensively in paleoclimate studies. The separation of clay minerals from sediments/soils, using various chemicals, is a prerequisite for isotope ratio measurements, where carbonate, Fe-(oxyhydr)oxides, and organic matter are removed successively from the sediments for a greater clay yield. The commonly adopted organic matter-removal method using hydrogen peroxide (H2O2) is thought to either alter directly the pristine δ2H values of the smectite clay minerals or to introduce organic hydrogen-bearing impurities through the ineffective removal of organic matter. The objective of the present study was to test whether H2O2 treatment can alter the δ2H values of kaolinite (Kln) by comparing two organic matter-removal methods, namely, H2O2 and disodium peroxodisulfate (Na2S2O8) combined with a neutral buffer. In doing so, kaolinite-rich, old (~56 Ma) sediment samples and pure kaolinite internal laboratory reference materials were used to understand the effectiveness and suitability of the above-mentioned methods in clay-sample preparation for δ2H measurements. The δ2H values of the H2O2-treated aliquots show smaller δ2H values than those for the Na2S2O8-treated aliquots. Estimated ambient water δ18O values (−4‰) from the Na2S2O8-treated aliquots agreed well with the bio-phosphate (fish vertebrae) based environmental water δ18O estimation (−3.3‰). The present study indicated, therefore, that δ2H values obtained after Na2S2O8 treatment are likely to be more realistic for paleoclimate reconstruction.