Subjects of contemporary research in Benelux are enumerated.

In the first part of this paper the formation processes of pure octahedral hydroxides are investigated. Conditions of synthesis of aluminum, magnesium, iron and mixed Al-Mg, Al-Ca, Al-Fe systems are successively reviewed. In every case crystal growth in deionized medium allows one to figure out genetic conditions.

The second part deals with the conditions required for the development of the octahedral layer in the presence of silica, i.e. the clay mineral synthesis. Experimental conditions remain always as nearly as possible to those observed naturally.

Trioctahedral minerals are rather easily obtained at ordinary temperature and pressure. The evolution of the magnesium-silica system is described. Synthesis of dioctahedral layer lattices, such as those of the kaolin minerals, appears more difficult to perform under the same conditions. Initial organization of the starting materials plays an important role in this case and procedures are described.

Finally, interactions of octahedral and silica layers are studied. The study of infrared spectra in the 9–11μ region permits such observations. Characteristic changes in the spectral region of Si-O stretching allows one either to follow the octahedral destruction (by acid attack or dehydroxylation) or the octahedral layer formation in kaolinite synthesis.

Sediments of the Tuscaloosa Group, Upper Cretaceous Age, crop out in an arc that extends from North Carolina through the kaolin districts of South Carolina and Georgia, across Alabama, Tennessee, Kentucky and into southern Illinois. Deposits of clay, sand, and gravel were formed in a variety of geologic environments that include marine, lacustrine, lagoonal, fluvial and deltaic deposition. They accumulated on an eroded surface of pre-Triassic rocks.

In eastern Alabama clay beds within the Tuscaloosa Group that occur close to the contact of the pre-Cretaceous crystalline rocks comprise detrital accumulations derived from saprolite, and consist of kaolinite, montmorillonite, chlorite and quartz. Clays occurring somewhat stratigraphically higher in this section are mixtures of illite, kaolinite, quartz and minor amounts of montmorillonite and chlorite.

Westward in Alabama, clay in the Tuscaloosa Group occurs as thick irregular pockets and lenses of montmorillonite clay, whereas, in northwestern Alabama the clay is kaolinite with variable amounts of illite and montmorillonite. Some of the clay deposits in this area have been lateritized, resulting in the formation of bauxitic clay, which is a mixture of gibbsite and kaolinite.

Mineralogical and chemical properties of Madison soil derived from quartz mica schist reflected the degree of weathering. The Madison soil had sandy surface horizons and clayey B horizons. The clay in surface horizons contained more mica than clay in the subsoils; a maximum of about 40 per cent mica in the coarse clay of surface horizons. Intergradient chlorite-vermiculite was present in appreciable quantities in clays of surface horizons. The presence in the whole soil of B2 horizons of about 15 per cent gibbsite and 12 per cent free iron oxides indicated a high degree of weathering. Kaolinite and gibbsite increased with depth and were the major clay minerals in all clay fractions in the lower portion of the profiles. Kaolinite and gibbsite also were important accessory minerals of the coarse and medium silt fractions and increased in percentage with depth. The B3 horizons had much of the morphology of the schist. Results indicated a high weathering intensity in the subsoil and leaching of weathering products.

A substantially homogeneous mineral fraction from a Katy soil profile in Fort Bend County, Texas, consists of a tabular kaolin group mineral with the physical and chemical properties characteristic of a nearly dehydrated halloysite, retaining only a small excess of water.

Clays from two Reddish-Brown Lateritic soils from the southern Mississippi Coastal Plain were fractionated and the mineral associations and weathering transformations were examined. The clays were found to be dominated by well-chloritized expansible layer silicates, gibbsite and kaolinite, with smaller amounts of quartz, mica and anatase. The abundance of gibbsite appeared to be related to the presence of expansible layer silicates and to soil pH variations. This mineral and kaolinite were found in appreciable amounts in even the finest clay fractions. Quartz and mica decreased to insignificant amounts with soil depth and decreasing particle size whereas gibbsite content of the clays rose suggesting an interrrelationship between these minerals.

This paper describes a method and apparatus for separating clay particles according to their ability to store electrical energy. Separation is accomplished by opposing an electrical dielectrophoretic force by a mechanical centrifugal force. The apparatus used to create these forces consists of an axially rotating, fluid-filled cylinder in which a non-uniform electric field is maintained by means of radially disposed electrode vanes.

The behavior in this separator of illite, prochlorite, montmorillonite, halloysite, and kaolinite is reported. Observed differences in the dielectrophoretic force acting on these clays indicate that they can be separated one from another by this method.

The basic equations which govern the motion of particles in this separator are discussed. From these equations and known electrical properties of clays it is concluded that the large dielectrophoretic force which acts on a clay particle must have its primary origin in an interaction between the non-uniform electric field and induced ionic space-charge which presumably is created in the particle’s interlayer regions and in the loosely associated external surface layer.

Samples of altered volcanic materials, interbedded with dominantly carbonate sediments, were collected from Ordovician, Silurian, and Devonian strata in Michigan, Illinois, Kentucky, Pennsylvania, Virginia, and Alabama. These altered volcanics, originally called metabentonite and more recently K-bentonite, occur in thin seams commonly only a few inches thick and are generally believed to be altered Paleozoic volcanic ash falls because they contain typical igneous minerals in the heavy suite and retain textures and structures characteristic of ash deposits.

Petrographic, differential thermal, and X-ray analyses were made of these samples to determine the clay mineralogy. Mixed-layer illite-montmorillonite occurs in the majority of samples. Illite is present in all samples and chlorite occurs in a few samples. This is in general accord with findings of previous studies. The mixed-layer clay is believed to have been deposited as montmorillonite in a marine environment and subsequently altered largely to illite through fixation of K in the interlayer position.

K-bentonites from Michigan and Illinois contain a constituent which has a 7.6 Å d-spacing. It is suggested that this material may be of regional significance because its occurrence was confined to the Upper Mississippi Valley K-bentonites in samples of this study.

The electron microprobe has been used to analyse mixtures of fine-grained silicates such as clay minerals in order to determine directly how cations distribute themselves between mixtures of two fine-grained ion-exchanging materials in pure water and in dilute solutions.

Cation distributions have been determined for mixtures of:

1. (a) a zeolite, faujasite, and the clay mineral in an Arizona bentonite

2. (b) the clay mineral in an Arizona bentonite and hectorite; and

3. (c) three synthetic beidellites of varying charge density.

Distributions have been found for varying ratios of Ca to K ions in the suspensions. The results for the faujasite-bentonite mixture show complex behavior and exhibit curves with maxima and minima. For the system bentonite-hectorite most of the Ca goes to the montmorillonite in the bentonite. For the mixture of synthetic beidellites, the results are rather confusing but it appears that the calcium is more associated with the beidellite with the highest exchange capacity. In all these systems, hydrolysis takes place and the hydronium ion plays a part in determining the equilibrium.

X-ray diffraction techniques were used to identify the clay mineral assemblages of Pennsylvanian underclay samples taken mainly from beneath the Colchester (No. 2) and Herrin (No. 6) Coals of Illinois and the Middle Kittanning Coal of Ohio. The clay minerals present are kaolinite, illite, chlorite, vermiculite, montmorillonite, and mixed-layer clay minerals. The minerals are not restricted to any particular stratigraphic unit, and their areal distribution is related to paleogeographic position in the original basin of deposition. Kaolinite shows a decrease in abundance from near shore to more basinward areas; illite is not present in near shore regions, becomes common basinward, and then shows a decrease with increasing distance from shore; chlorite is not found in near shore or in extreme basinward areas but is most common slightly basinward of the illite maximum; montmorillonite is fairly rare but is prominent in the most basinward positions; vermiculite is uncommon but usually occurs where kaolinite is the dominant mineral; mixed-layer clay minerals are present in all samples, constituting a small fraction of the clay minerals in the near shore regions but increases to the major constituent in the most basinward areas.

Clay minerals entering the basin of deposition during underclay formation were mainly kaolinite and mixed-layer clay minerals. As the mixed-layer clays were carried basinward into waters of increasing salinity, some of the mixed-layer clays, formed from weathered illite and chlorite, preferentially adsorbed potassium and magnesium and were regraded. Mixed-layer clay minerals that had undergone severe structural damage during weathering were not regraded and were deposited further basinward.

Maps showing lateral variation of clay minerals in an underclay also show the paleogeography. These maps may be used in outlining positive areas and deltas, or specific types of clay deposits.

Novel polymer-clay compositions were synthesized by neutralizing hydrogen montmorillonite and hydrogen kaolinite with amine-terminated polystyrene. The latter was obtained by the amide ion-initiated polymerization of styrene in liquid ammonia at −33°C. The neutralization reactions were carried out in methyl ethyl ketone, acetone, N,N-dimethylformamide and their aqueous solutions. As a result of their chemical modifications, the clays change from hydrophilic to hydrophobic, organophilic substances. Polystyrene-montmorillonite compositions containing about 50 per cent by weight of combined polymer formed dispersions in hydrocarbon oils which were similar to high temperature lubricating greases. The basal spacings of the organo-montmorillonites indicate the deposition of a polymer layer one molecule thick.

Distinction between the non-expanding three-layer clay minerals, illites, and the expanding three-layer clay minerals montmorillonites is accomplished by glycolation treatment. Distinction among the montmorillonites can be accomplished if the interlayer cation, type and amount of adsorbed liquid, and particle size are kept constant. With these variables constant, the expansion of montmorillonites can be correlated with particle size and/or charge on the tetrahedral layer.

Sodium saturated montmorillonite samples taken from 0–100 per cent relative humidity generally exhibit three hydration levels. Coarse fractions and fractions that possess high charge densities per unit area, compared to fine fractions and fractions that possess low charge densities per unit area, expand the most at low humidities and expand the least at high humidities. This is explained by cation or surface hydration and the strength of the bond between the layers. Introduction of potassium into the interlayer positions of the montmorillonite lattice decreases the ability of the silicate layers to expand. Examination of the diffraction patterns reveals that physical combinations of particles with different hydrations, interlayer mixtures of hydrates, and interlayer mixtures within the physical combinations have been produced.

A working definition for allophane includes amorphous silica and alumina that are quickly soluble in boiling n/2 NaOH. Kinetic studies are used to differentiate and to make a rough estimation of the amount of allophane and certain other impurities present in some kaolin minerals.

Solution rate studies on opal, gibbsite, two allophanes, volcanic ash, quartz, two halloysites, and two kaolinites are presented and in most cases the reaction rate orders with respect to the hydroxide treatment are determined. No interpretation of the observed rate orders are presented.

The decomposition of the two kaolinites followed a third order rate law and their rate constants varied approximately by a factor of ten. The decomposition of the two halloysites followed a second order rate law and their rate constants varied approximately by a factor of five. It is not known why specimens of the same mineral species from different localities should have such large variations in their dissolution rates. Differences in their degree of crystallinity and the resulting surface area may be responsible.

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.