bluuebunny/crossref_metadata_2025 huggingface dataset:
Nonmontmorillonitic Composition of Some Bentonite Beds
Authors: Schultz L. G.
Published: August 2006

Although the wide range of minerals resulting from alteration of tuffaceous rocks under hydrothermal and weathering conditions is well known, the extent of variation in composition of discrete bentonite beds subjected only to normal diagenesis and compaction is perhaps less well known.

Three bentonite samples from the Atoka Formation of Pennsylvanian age are predominantly mixed-layer illite-montmorillonite with subordinate kaolinite. Most bentonites in the Fierre Shale of Late Cretaceous age are entirely montmorillonite, but a few contain some kaolinite; one is predominantly kaolinite; some also contain appreciable interlayer Al(OH)3 or Mg(OH)2 forming a mixed-layer montmorillonite-chlorite clay; several are composed of considerable clinoptilolite, and one is largely phillipsite. Bentonite beds in the Carmel Formation of Middle and Late Jurassic age differ among themselves in composition; in a few, illite is the dominant clay; in others, mixed-layer chlorite-montmorillonite-illite in different proportions is the dominant clay; kaolinite is common and makes up nearly half of one sample. A rhyolite tuff near Denver, Colorado, has been altered to halloysite. Reasons for variation in the composition of these bentonites are only partly understood.
Compaction of Clay Sediments in the Range of Molecular Particle Distances
Authors: van Olphen H.
Published: August 2006

The physical process of compaction of clay sediments and the inverse process of swelling can be discussed in terms of particle interaction forces. The swelling pressure in a given situation equals the nct repulsive force per unit area between the particles. The net repulsive force is the resultant of various repulsive and attractive forces. Two stages of swelling or compaction can be distinguished, one in which the particles are relatively far apart, and a second in which they arc separated by only a few monomolecular layers of water.

In the first stage the swelling pressure is primarily due to double-layer repulsion (“osmotic swelling”). The pressures range from a fraction of one atmosphere to several times ten atmospheres. These pressures are of particular interest for foundation engineering problems.

In the second stage the swelling pressures are dominated by the work of adsorption of the water layers on the clay surfaces. Tile pressures may reach several thousand atmospheres. Quantitative data on the swelling pressures in this range are derived from water vapor sorption isotherms combined with X-ray data on the c-spacing of expanding clays during dehydration.

It is concluded that overburden pressures in nature will seldom be high enough to remove all adsorbed water from between parallel grain surfaces.
Mineralogy of Ordovician K-Bentonites in Kentucky
Authors: Huff Warren D.
Published: August 2006

Preliminary results of investigations of Trenton-Black River (Ordovician) K-bentonites from well cores in northern Kentucky and from outcrops along the Kentucky River illustrate the variations in some physical and chemical properties. It is hoped that some features may eventually be useful in stratigraphic correlation, considering that the very nature of these altered ash beds makes them ideal time-lines.

That these beds are derived from volcanic ash is evidenced by significant amounts of biotite, magnetite, leucoxene, apatite, and zircon.

The following means of investigation have been employed: X-ray diffraction, DTA, cation exchange, heavy mineral studies, and insoluble residue studies of adjacent limestones. X-ray analyses of untreated and glycolated clay samples indicate a mixed-layer, dioctahedral, illite-montmorillonite type structure with an I-M ratio varying from 4:1 to 3:2. The proportion of expandable layers in many samples is higher than that reported for Ordovician K-bentonites elsewhere. No evidence of chlorite is detected.

DTA data show a primary hydroxyl peak near 725°C suggesting a basic montmorillonite-type of hydroxyl bonding. Treatment with 1M solutions of various cations produces a slight expansion of the expandable layers with Ca2+, and contraction with Na+, K+, and NH4+ giving some indication of original environmental composition. The evidence supports suggestions by earlier authors that the clays are basically montmorillonites which have undergone partial contraction due to the adsorption of potassium in the interlayer positions.

While euhedral zircons are most likely non-detrital, recent work on zircons in igneous rocks suggests the same may also be true for some of the sub-rounded and fractured species.

Insoluble residues of limestones contain abundant chert and mixed-layer illite-montmorillonite clay directly adjacent to the ash beds, but farther away illite and chlorite dominate and are probably detrital in origin.
Clay Formation and Accumulation in Selected Oklahoma Soils
Authors: Gray Fenton , Reed L. W. , Molthan H. D.
Published: August 2006

The clay minerals were studied from eleven soil profiles representing three Great Groups of eastern and central Oklahoma. Montmorillonite and illite type clay minerals were found to be the dominant minerals; montmorillonite dominates the fine clays; illite is the chief constituent of the coarse clays. The fine clays dominated the clay fraction of most horizons, including the parent material. The results of the investigation indicate that the present régime of soil formation has had little effect in altering the clay minerals of the soil from those present in the original sediments.
Identification of Kaolin Minerals in the Presence of Chlorite by X-Ray Diffraction and Infrared Absorption Spectra
Authors: Kodama Hideomi , Oinuma Kaoru
Published: August 2006

Experimental data are presented to show that the current auxilliary procedures adopted for identification of kaolinite in the presence of chlorite are not generally valid because the procedures often fail to give an explicit condition for distinguishing both the minerals.

As the result of an examination of numerous infrared spectra in the OH region of clay minerals, obtained by using Nippon Bunko DS-401G Grating Speetrophotometer, it turned out that the absorption band at 3698±2 cm−1 is effective for distinguishing kaolinite from other clay minerals without the use of any additional techniques. The absorption band seems to be less affected by variation of particle size and crystallinity than is the X-ray diffraction pattern. The band is detectable to a few weight percent of kaolinite in total amounts of clay minerals. Identification of kaolinite by its absorption spectrum in clay samples from sedimentary rocks was successful.
Mechanism of NH3 Adsorption by Montmorillonite and Kaolinite
Authors: James D. W. , Harward M. E.
Published: August 2006

Dry, homoionic systems of two montmorillonites and a kaolinite were treated with NH3 and then evacuated exhaustively to eliminate any physically adsorbed ammonia. It was concluded that the NH3 retained by the minerals was associated with the exchangeable cations. The mechanism of this adsorption process is the same as that which leads to the formation of inorganic ammines, namely, the mutual attraction between unshared electrons in the NH3 molecules and ionic centers of positive charge. This sorption process is reversible at elevated temperatures and is described by the equation, nNH3 + CX ⇄ (nNH3 · C)X, where n is the number of NH3 molecules associated with each exchangeable cation, C, on exchange complex X. Accordingly, n is a coordination number and has the following values for the cations indicated: NH4, 0; K, 0; H, 1; Ca, 2; Mg, 2; Alin, 3; Alex, 6. Here in and ex refer to interior and exterior exchange sites respectively. The retention of NH3 by cations which saturate the exchange complex of clays was shown to be analogous to the formation of ammoniates by reaction of NH3 with inorganic salts.

A reduced retention of NH3 by the Mg and Al 1:1 systems was ascribed to the possibility that exchangeable Mg and Al on kaolinite occur as hydroxy complexes.

A significant amount of NH3 was adsorbed to the weak acid hydroxyl groups on the broken clay edges, Relative to exchange capacities this phenomenon was greater in magnitude on the 1:1 than on the 2:1 clays.

Energies of NH3 adsorption on CaCl2, Ca-bentonite and NH4-bentonite were determined. Values of △H as a function of temperature were shown to be different for the Ca and NH4-clay systems. The data indicated stronger energies of retention of NH3 by the Ca-clay than for the NH4 clay. The thermodynamic data thus support the mechanisms proposed here.
Crystallographic Aspects of High Temperature Transformations of Clay Minerals
Authors: Taylor H. F. W.
Published: August 2006

This paper deals with the dehydroxylation reactions of clay minerals and allied substances such as lamellar hydroxides, serpentine minerals, and amphiboles. Probably in all cases, these reactions occur topotaxially, that is, there is a three-dimensional similarity between the crystal structures of starting material and product, as a result of which each crystal of the starting material is changed into something approaching a single crystal of the product. Many investigators have studied the orientation relationships between starting materials and products, and their results have provided the main experimental foundation for hypotheses about the reaction mechanisms. These hypotheses have, however, rested also on assumptions, of which until recently three have usually been made. These are (i) loss of water occurs more or less uniformly from all parts of the crystal; (ii) the Si-O parts of the structure are more stable than the metal-oxygen parts; and (iii) the silica-rich material often presumed to be formed as a subsidiary product is pure SiO2. Recent work suggests, however, that none of these assumptions is securely based, and the purpose of this paper is to suggest an alternative approach to the problem.

The high temperature reactions of clay minerals are perhaps best understood by treating the latter as assemblies of close packed, or nearly close packed, oxygen ions with cations in the interstices. From this point of view, one might expect that the relatively small cations, such as Si4+, Al3+, Mg2+, and especially H+ would move more easily than the oxide ions. One would not expect the oxygen atoms that are lost as water to be necessarily those present initially as OH- groups; they are more likely to be those that can most easily escape from the structure, e.g. from near external surfaces or grain boundaries. On this hypothesis, a typical dehydroxylation reaction involves three types of process:

Loss of oxide ions from exposed or “donor” regions, and their combination with H+ ions from all regions, to form water. The donor regions are changed into pores.

Cation migrations. These may be of two kinds. Firstly, all cations other than H+ migrate from the donor regions into the remaining or “acceptor” regions, and H+ ions migrate in the opposite direction. Secondly, within the acceptor regions themselves, further migrations may cause differentiation into Si-rich and Si-poor parts to occur.

Changes in the type of oxygen packing in the acceptor regions, to complete the formation of the crystalline products. These last changes may occur throughout the acceptor regions, or only in certain parts of them.
Electrical Resistance Measurements of Kaolinite and Serpentine Powders During Dehydroxylation
Authors: Nakahira M.
Published: August 2006

Direct current resistance measurements were made of kaolinite and serpentine powders to follow the changes in resistances during their dehydroxylation processes in air. The resistance of kaolinite remained almost constant during the dehydroxylation, whereas that of serpentine showed a rapid decrease. The formation of distorted lattice sites where the charge carriers are scattered under an electric field was assumed in the former case. On the other hand, the result in the latter case was interpreted in terms of an increasing cation mobility.
Kinetics of the Thermal Dehydration of Hydrous Silicates
Authors: Holt J. Birch , Cutler Ivan B. , Wadsworth Milton E.
Published: August 2006

Generally, the rate of dehydroxylation of clay minerals may be controlled by reaction at the interface between the decomposed and undecomposed mineral, diffusion through the decomposed phase and/or nucleation of the decomposed phase. Only in rare instances are mineral decomposition reactions homogenous. Some examples are presented to illustrate these principles.

For macrocrystalline muscovite the initial sample weight rather than the external surface area was found to be a parameter of the rate of weight loss. Upon grinding the muscovite to particles smaller than — 65 mesh, an internal surface area factor strongly influenced the rate. This surface area was related to dislocations shown to be present in muscovite.

A rate equation is presented that explains the observed weight loss versus logarithm of time dependence based on a model involving a systematic relief of strain during dehydration.

The rate equation for pyrophyllite was exactly the same as that formulated for muscovite. As with muscovite there was a change in free energy of activation throughout the dehydration process. In contradiction to muscovite, the contribution to the free energy of activation was at least partly enthalpy while with muscovite it was an entropy of activation contribution.

The dehydration of kaolinite was carried out in vacuum. At pressures of one micron the reaction was found to be diffusion controlled with hydroxyl ions as the likely diffusing species.
Studies on the Properties and Formation of Quick Clays
Authors: Osterman Justus
Published: August 2006

In a natural clay, the occurrence of a high sensitivity, i.e. a high quotient between the shear strength of the undisturbed and remolded soils respectively, under undrained conditions, is connected to thixotropic effects and to “quickness”.

The general composition of the soils in which quick clay occurs is described, and mention is made of the occurrence of non-argillaceous rock fragments in a matrix of clay particles. Mite is the main clay mineral. Quickness occurs both in salt-leached, marine deposited clays and in clays deposited in fresh water. The pore water of these clays is low in electrolytes and undecomposed organic material. It is found that quick clays often occur near peat and similar humic deposits. Also briefly discussed is the internal stress distribution in natural clays under various consolidation conditions, the structure of quick clays and their conditions of formation. The consistency of clays is considered, as is the stability and coagulation conditions of suspensions. This is followed by a commentary on physico-chemical effects contributing to the formation of quick clays under natural conditions, and a discussion of the salt-leaching theory and the theory on the effect of peptizing agents.

In the discussion, the author draws parallels between the coagulation and the thixotropic phenomena, and between the stability and dispersion of suspensions and the quickness.
Clay Alteration in Copper Deposits Associated with Granodiorites
Authors: Meyer Charles
Published: August 2006

Recent development at deep levels in the Mt. Con Mine at Butte, Montana, has revealed a structurally early alteration type characterized by K-rich alkali feldspar, brown and green biotite, and 2M muscovite (sericite). This is similar to the K-rich biotite assemblage in numerous porphyry coppers as emphasized by Anderson, Gilluly, Creasey, and Rose. In Butte, and in some of the porphyry coppers, the assemblage is demonstrably earlier than the common feldspar-free, muscovite-quartz-pyrite assemblage which envelops pyrite-rich veinlets. On the other hand, few consistent mineral assemblages or detailed distribution patterns have yet emerged for argillic alteration, where illite, kaolinite, montmorillonite, and locally allophane and pyrophyllite are prominent phases. Probably much of the confusion results from extensive supergene alteration, though even this cannot be proved at present.

In supergene and in hypogene alteration at least below 300°C, supersaturation of SiO2 in the aqueous phase may play an important role in determining alteration assemblages. Some reactions affected ar. (1) the hydrolysis of K-spar to K-mica. (2) albite to montmorillonite. (3) silica-rich illite or montmorillonite to kaolinite, an. (4) pyrophyllite to kaolinite.

The encroachment of the sericitic zone on the argillic zone at Butte may be controlled by changes in ionic species of the veinward migrating SiO2 liberated by argillization of plagioclase. Within the sericitic zone and the veins, silica in solution is probably in equilibrium with quartz.
The Origin of High-Alumina Clay Minerals—A Review
Authors: Keller W. D.
Published: August 2006

High-alumina minerals refer, in this paper, to Al-rich, normal sedimentary phases, including gibbsite, boehmite, diaspore, possibly “proto-diaspore” and “proto-alunite”, “Al-chlorite”, and corundum, in association with kaolin minerals. They may be derived from any common Al-containing rock. Processes of origin include direct bauxitization of non-clay silicate minerals and rocks, and the desilication of any of the common clay minerals, particularly of the kaolin group. Apparently aluminous gels were formed within certain marshy basins, and/or were transported into basins, giving rise to concretionary masses of high-alumina minerals. Concretionary deposits were formed by dissolution of Al and reprecipitation.

Alumina is probably more soluble, inherently, than is interpreted from geologic occurrences. Even after Al is dissolved under appropriate pH, or complexing reactions, its solubility is obscured by Al-immobilization through fixation within 3-layer clay minerals, or absorbed by other phases. A 14Å phase, probably aluminous, is not uncommon in certain soils, and in flint and boehmite-diaspore-containing clays. Subtraction of silica by plants, is accompanied by concentration of alumina.
Genesis of Kaolinite from Montmorillonite by Weathering: Structural and Morphological Evidence of Transformation
Authors: Altschuler Z. S. , Dwornik E. J. , Kramer Henry
Published: August 2006

Kaolinite originating by the low-temperature subaerial transformation of montmoril-lonite occurs extensively in Tertiary clayey sands of central and northern Florida. It occurs in gray iron-stained weathering zones, as much as several feet thick, that transgress primary green clays of the Bone Valley and other formations over hundreds of square miles. Subjacent deposits of opal and chert, clearly post-depositional, are a widespread byproduct of the transformation.

Kaolinization begins as a hexagonal modification of the edges of montmorillonite flakes. X-ray study reveals that montmorillonite degrades and disappears up-section, with the appearance of the 7.2 kaolinite reflection and a very small 20–21 Å reflection. The altered clay loses silica and gains alumina and water.

The clay transformation apparently proceeds by intracrystalline leaching of tetrahedral silica layers by slightly acid ground water. Approximately regular interposition of resultant stripped packets within montmorillonite creates a regular 1:1 mixed-layered montmorillonite-kaolinite, which responds as montmorillonite does to glycolation and heating. The stripped kaoline-like packets develop hexagonal outgrowths of true kaolinite by lateral epitaxy. Nourished by the decomposing montmorillonite, the outgrowths enlarge and nucleate new vertical growth, observed as oriented crystallites, 40–50 Å thick.

Transformation of montmorillonite to kaolinite is a major geochemical process: creating goethite-stained kaolinitic sands of regional extent, liberating much silica for chert deposition and ground-water enrichment, and constituting an eluvial process that leads, in some areas, to residual quartz sand plains.
High-Temperature Phase Development in Illitic Clays
Authors: Bohor Bruce F.
Published: August 2006

Five illitic clays were treated with various inorganic cations and heated to over 1400°C in a high-temperature X-ray diffraction furnace.

The illite lattice undergoes dehydroxylation from 475–600°C, and the resulting anhydrides begin to disappear at 850°C. The major high-temperature phases formed from untreated illites are β-quartz (1000–1300°C), spinel (1000–1400°C), and mullite (1150–1400 +°C). Minor amounts of cordierite, kalsilite, feldspar, corundum, iron oxide and forsterite may also occur with various adsorbed cations at temperatures above 1000°C. β-cristobal-ite was never observed in any of the runs, contrasting strongly with its prominent development among the high-temperature phases of montmorillonite.

Certain adsorbed cations act as repressors of high-temperature phase development, while others seem to have the opposite effect. The order of decreasing repressive effect— K+> Na+> Li+> Ca+2> Mg+2> Be+2> Sn+2,4—also represents the sequence of increasing electronegativity and ionic potential of these cations. It is postulated that the degree of electronegativity and ionic potential of the adsorbed cations is proportional to the rapidity and degree of mullite crystallization, because of the influence of these factors in ion transfer and reaction product removal in the critical liquid phase at the clay mineral surface.
The Structure of Organic Montmorillonites and Their Adsorptive Properties in the Gas Phase
Authors: White D.
Published: August 2006

Previous work has shown that dimethyldioctadecyl ammonium montmorillonite is a very effective adsorbent in the gas phase for the separation of aromatic compounds from the paraffins, and for the separation of the disubstituted isomers of benzene. The present paper describes an investigation into this phenomenon.

For this purpose a method of calculating entropies of adsorption from gas chromatographic data was derived, and results are given for relevant organic vapours adsorbed on the quaternary ammonium derivative, and on octadecyl ammonium montmorillonite. These results throw considerable light on the basis of the selectivity shown by the quaternary ammonium derivative, and a possible explanation of the mechanism is given.

The effect of the method of preparation on the gas phase activity of this adsorbent is very large, and experimental work on the correlation of this with the structure of the derivative is described.
Electrokinetic Properties of Lime-Treated Bentonites
Authors: Ho Clara , Handy R. L.
Published: August 2006

Zeta-potentials of Na- and Ca-bentonites treated with varying amounts of Ca(OH)2were measured by a Northrop-Kunitz horizontal cell and non-polarizing Zn-ZnSO4electrodes. 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)2is 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)2in 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.
Potentiometric, Electrical Conductance and Self-Diffusion Measurements in Clay-Water Systems
Authors: Gast R. G. , East Peggy J.
Published: August 2006

Potentiometric measurements using commercially available cationic glass electrodes, electrical conductance and self-diffusion measurements of cations and water were made in electrolyte-free 3–5 per cent Li, Na, K, Cs, Ca and Sr bentonite-water systems and bi-ionic systems with varying ratios of K and Ca. Activation energies for conductance in the homoionic clays were calculated using the Arrhenius equation.

The agreement between cation mobilities measured by diffusion and conductance indicates that the underlying mechanism is essentially the same for the two processes. But the activation energies for ion movement determined for conductance measurements do not explain the observed reduction in mobility. Only two clays, Li and Cs, gave values significantly higher than for the measured solution conductance and only the Cs clay gave a value higher than those calculated for ion conductance at infinite dilution.

Increasing Ca saturation in K-Ca clays from 1 to 99 per cent increased the self-diffusion coefficient or mobility of K by a factor of about 1.7 and Ca by a factor of about 30 reflecting the effect of the predominate accumulation of the divalent cation in regions of highest negative potential. The reduction in activity of monovalent cations calculated from the potentiometric measurements, although of the same order of magnitude, was consistently less than the corresponding reduction in mobility in both the homoionic and bi-ionic clays. This difference became greater with increasing mobility of K in the bi-ionic clays.
Transformation of Clay Minerals by Calcium Hydroxide Attack
Authors: Diamond Sidney , White Joe L. , Dolch W. L.
Published: August 2006

Calcium hydroxide was allowed to react with various clays, other silicates, and quartz at slightly elevated temperatures for several months. The reaction products were examined by X-ray diffraction, DTA, and electron microscopy, and were shown to be poorly-crystallized calcium silicate hydrates of the tobermorite family, and calcium aluminate hydrates. Quaternary phases were not detected, but some isomorphous substitution probably occurred. The extent of reaction was shown to be such that under appropriate conditions almost all of the clay mineral was decomposed. Electron micrographs of the reacted materials indicated that attack occurred from the edges of the particles, and in general the remaining unattacked portion of the clay did not suffer appreciable loss of crystallinity. It was postulated that the reaction involved progressive dissolution of the mineral at the edges of the particles in the strongly basic environment maintained by calcium hydroxide solution, followed by separate precipation of the reaction products.

In these experiments the calcium silicate hydrate generated by the reaction between lime and quartz was uniformly calcium silicate hydrate gel (CSH (gel)); reaction with kaolinite and montmorillonite produced either CSH (gel) or calcium silicate hydrate (I) (CSH (I)) depending on the conditions of the reaction. At 60°C the alumina-bearing phase was tricalcium aluminate hexahydrate; at lower temperature the phase produced was a hexagonal material closely resembling 4CaO.Al2O3.13H2O (C4AH13) but retaining a constant 7.6Å basal spacing regardless of its state of wetness or dryness.

It was found that under appropriate conditions the formation of CSH(I) resulted in as effective a cementation as did the formation of CSH (gel).
Cation-Exchange Constants for Clays from Electrochemical Measurements
Authors: Hanshaw Bruce B.
Published: August 2006

Ion exchange constants for various cations adsorbed on clays were determined using compacted-clay samples as membrane electrodes and theory for the membrane response of glass electrodes. The electrochemical cell used is conventionally written:

A static electrical potential is developed between the reference electrodes. The potential is a function of the cation species and of the cation activities in the two solutions and is given by an adaptation of the Nernst equation. From measurements of the electrical potential, the free energy of reactions or exchange constants for a series of reactions between various cation species were obtained. These determinations indicate that compacted clays prefer monovalent over divalent cations.

Some exchange constants were determined for the same clays in a non-compacted state. Not only the magnitude but also the order of cation selectivity changed for the same clay when determinations were made in the dispersed state and compared with those obtained by electrochemical means using compacted clay. Publication authorized by the Director, U.S. Geological Survey.
Vermiculite Surface Morphology
Authors: Raman K. V. Venkata , Jackson M. L.
Published: August 2006

A study of the surface morphology of vermiculites from several different sources by the electron microscope has indicated that, unlike the smooth surfaces of micas, the vermiculite surfaces show micromorphological structural variations such as small humps, prominent crystallographic steps on the basal cleavage planes, marginal rolling of the layers and layer buckling. The production of layer buckling may result from the inhomogeneity of interlayer population caused by the introduction of hydrated cations replacing potassium during weathering. The (110) steps on the surface of the cleavage can be observed and these are visualized as nuclei for weathering in addition to the particle edges.

The surface morphology of vermiculites is closely related to the nature of the interlayer cation. When treated with potassium or ammonium salts, the surfaces assume smooth morphology, the K and NH4 ions occupying interlayer sites and collapsing the mineral. When treated with Na or Li salts, the complex surface morphology persists, and in some cases is enhanced, possibly by the slow exchange of residual potassium from the interlayer. On this basis, the presence of unweathered mica cores have been identified in natural vermiculites which show varying amounts of residual K2O content. It is possible to offer an explanation from structural considerations for the complex morphology of the vermiculite surfaces including the curling of the layers on depletion of potassium. The morphological features of vermiculites have been produced on biotite mica by leaching with salt solutions.
Clay Deposits of the Tuscaloosa Group in Alabama
Authors: Clarke Otis M.
Published: August 2006

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.
Occurrence of a Tabular Halloysite in a Texas Soil
Authors: Kunze G. W. , Bradley W. F.
Published: August 2006

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.
NaOH Dissolution of Some Oxide Impurities from Kaolins
Authors: Langston R. B. , Jenne E. A.
Published: August 2006

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.
Weathering and Transport of Sediment in the Cheyenne River Basin, Eastern Wyoming
Authors: Rolfe B. N. , Hadley R. F.
Published: August 2006

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.
Kaolinite Stability in the Central Piedmont of Georgia
Authors: Grant Willard H.
Published: August 2006

A study of weathered profiles from fresh rock to the
surface in granitic rocks and biotite-plagioclase gneiss shows the
following: 1. The particle size of the kaolin increases from not subject to
estimate in fresh rock to a maximum of approximately 60
μ in the vicinity of the contact between the
B horizon and the saprolite, then it decreases to approximately 13
μ in the A horizon. 2. Gibbsite occurs most
abundantly when the abrasion pH of rock slurries is greater than 6 or less
than 5.5. In outcrop, gibbsite is abundant in the upper soil horizons and in
the partially weathered rock but is sparse in the intervening saprolite. 3.
The total amount of kaolin increases steadily upward from zero in fresh rock
to a maximum in the B horizon then declines sharply in the A
horizon.

These data are interpreted to mean that kaolin forms, grows and is
stable in saprock, saprolite and B horizon, but it is not stable in the
upper B and A horizons or in the very basic environment of incipient
weathering.
Interstratified Montmorillonite-Mica Clays from Subsoils of the Prairie
Provinces, Western Canada
Authors: Kodama H. , Brydon J. E.
Published: August 2006

Samples of glacial till and lacustrine soil clays
selected over a distance of 900 miles across the Canadian Prairie Provinces
were examined in detail by X-ray, chemical, thermal, infrared-absorption and
electron-microscope methods. All of the experimental evidence indicated a
marked similarity among the samples. The dominant component was an 18 Å
phase when glycerol-solvated, which was identified as a randomly
interstratified montmorillonite-mica. This was associated with minor amounts
of a 10 Å phase (randomly interstratified mica-montmorillonite), kaolinite
and quartz. Fourier transforms of the basal series of reflections gave
contents of expanded material (montmorillonite) near 55 per cent, whereas
calculation of the chemical formula gave near 80 per cent montmorillonite in
the interstratified component. The Fourier transforms confirmed the random
nature of the interstratification but also showed a tendency to zonal
segregation of the mica and montmorillonite layers. On the basis of the
chemical formula, the Greene-Kelly test and the infrared spectra, the
swelling layer composition was intermediate between that of beidellite and
that of Wyoming bentonite.

Although there were no large differences between the samples, the small
differences suggested two trends differentiating the till samples and the
lacustrine samples: (1) The proportion of the expanded component of the
interstratified mineral tended to be less in the lacustrine than in the till
samples. (2) The composition of the expanding layers in the lacustrine
samples tended to be nearer to the Wyoming bentonite composition than were
the till samples. These trends are likely related to K fixation during or
after deposition of the lacustrine materials, whereby the expanding layers
with a beidellitic composition would be pre-empted leaving layers more
similar to Wyoming bentonite.
Clay Mineral Weathering in Southern Wisconsin Soils Developed in Loess
and in Shale-Derived Till
Authors: Fanning D. S. , Jackson M. L.
Published: August 2006

Loess is the dominant soil parent material covering
the western and central portions of southern Wisconsin. Glacial till derived
mainly from Devonian shales and Silurian dolomite is the most extensive
parent material in extreme southeastern Wisconsin. The soils developed in
loess are coarser in texture, leached of carbonates to greater depths and
more acid and contain a higher percentage of zirconium in their coarse silt
than those developed in the till. The clay of the soils developed in loess
contains a higher proportion of minerals of more advanced weathering indices
(montmorillonite, “pedogenic” chlorite and kaolinite) formed by weathering.
The clay mineralogy was fairly uniform in the four soils developed from
loess, but the two Gray-Brown Podzolic soils were found to contain only
about one-half as high a percentage of total clay and one-fourth as high a
percentage of medium and fine clay in their A horizons (which were also 7
in. less in thickness) than the A horizons of their prairie soil analogues.
The Varna soil developed in the till contains clay with a higher proportion
of minerals of less-advanced weathering indices (mafic chlorite and
dioctahedral mica), largely inherited from the parent material. There has
been some transformation of mica and mafic chlorite to expansible layer
silicates and amorphous material in the Varna solum and the ratio of ferrous
to total iron decreased both with decreasing particle size (from fine silt
through fine clay) and with approach to the soil surface (in the whole
clay).
The Occurrence of Sepiolite and Attapulgite in the Calcareous Zone of a
Soil Near Las Cruces, New Mexico
Authors: Vanden Heuvel Richard C.
Published: August 2006

Sepiolite and attapulgite were identified by X-ray
diffraction, elemental, and thermal analyses in the calcareous zone of a
soil formed on a relict basin-fill plain in Dona Ana County, New Mexico.
Sepiolite occurs in the lower part of the zone of calcium carbonate
accumulation; attapulgite occurs above, in, and below the sepiolite
zone.

The sepiolite was observed as whitish aggregates remaining after the
carbonate was dissolved with sodium acetate buffer (pH 5). Extended
treatment with this buffer dissolved a significant amount of the sepiolite
but did not appear to dissolve much attapulgite. Sepiolite was concentrated
for analysis without significant solution by separating the <100 mesh
material from the crushed soil, treating it with pH 5 buffer for a short
time and separating the carbonate-free clay. The sepiolite is relatively
high in aluminum compared to most sepiolites.

The sequence of dominant clay mineral with depth in the profile is
montmorillonite, attapulgite, sepiolite, attapulgite, montmorillonite. No
sepiolite or attapulgite was found above the calcareous zone; a little
attapulgite was found at the base of the profile, which was not totally free
of carbonates. Thin sections showed sepiolite and attapulgite occurring as
aggregates, as coatings on mineral grains and as small fibers. The
distribution of these minerals in the profile and the arrangement of the
small fibers in the calcrete suggest that these minerals crystallized during
the period of caliche formation.

As will be seen (Table 5) the sepiolite is present mainly in the nodular
calcareous zone; the attapulgite, mainly in the blocky calcareous zone and
in the transition zone below the calcareous zone (C6).
Infrared Absorption of O-H Bonds in Some Micas and Other
Phyllosilicates
Authors: Jørgensen Per
Published: August 2006

The frequencies, relative intensities and pleochroism
of OH stretching bands in some micas and chlorites were studied, and the
following conclusions are drawn

Trioctahedral 2:1 and 2:1:1 phyllosilicates, where all octahedral
positions are filled with Mg, will have an absorption band about 3700
cm−1. These OH-groups have their axes normal to the
mineral’s cleavage.

Substitution of Fe2+ for Mg results in a band about
3665 cm−1. Intensity ratios indicate that two
Fe2+ most commonly substitute for two Mg in the
same polyhedral group (pyramid).

Decreasing octahedral occupancy in the phlogopite-lepidomelane group,
with increasing substitution of R3+ for Mg, causes
bands with lower frequencies. These are not very sensitive to the incident
angle for the infrared beam. In Li-micas where less than 50 per cent of the
octahedral positions are filled with Li, and the rest of the positions are
filled with Al and Fe2+, it seems probable that
OH-groups residing in a pyramid with two Li and one Al cause a band about
3580 cm−1. Combinations of two Al and one Li or one Li,
one Al and one Fe2+ cause absorption about 3480
cm−1.

Dioctahedral 2:1 phyllosilicates having Al or Fe3+
in octahedral positions cause absorption about 3620
cm−1.
Early Reaction Determination in Two Hydroxide-Kaolinite Systems by
Electron Microscopy and Diffraction
Authors: Sloane Richard L.
Published: August 2006

Results of the study of the kaolinite-sodium
hydroxide interaction showed extensive dissolution of the kaolinite
structure at particle edges, with some production of “silicate relicts” as a
secondary effect. The method of specimen preparation for electron
micro-scopy precluded electron-diffraction study of soluble reaction
products. The study of the kaolinite-calcium hydroxide interaction revealed
a similar attack on particle edges and formation of “silicate relics” and,
in addition, formation of an insoluble reaction product that was tentatively
identified by electron diffraction as prehnite,
Ca2Al2Si3O10(OH)2.
Both studies showed an ephemeral phase that, by selected area elec- tron
diffraction, appeared to be a layer lattice silicate in (001) orientation.
In the calcium hydroxide-treated kaolinite, formation of the reaction
product was followed from nucleation along particle edges, after 24 hr, to
growth of particles about 0.5 to 1 μ in size
after 15 days. The combination of electron microscopy of surface replicas to
detect changes in morphology with selected area electron diffraction of
parallel pseudoreplicas for identification shows promise as a tool for study
of the early stages in mineral- chemical interaction.
Long-Term Settling Characteristics of Some Clays
Authors: Tobias T. J. , Ruotsala A. P.
Published: August 2006

A series of experiments was set up, the purpose of
which was to determine factors affecting long-term settling characteristics
of some suspensions of clay-sized materials. Suspensions of approximately 8
g per 1. were prepared using Georgia kaolin, Mississippi bentonite, Wyoming
bentonite, Iowa illite and finely ground quartz. In addition, 2 g and 16 g
per 1. suspensions of kaolinite were prepared. All suspensions were observed
for 2-week periods at constant temperatures of 19°C; kaolinite suspensions
were also observed at 2°, 10°, 25° and 31°C.

After settling 3–4 days at 19°C, layering formed in all clay
suspensions, and all the tops of the layers contained higher concentrations
of suspensoid than bottoms. Tops and bottoms of the layers were parallel to
liquid top surfaces.

At 2°C, no stratification developed in kaolinite suspensions. At 10°C,
layering formed only in 2 g per 1. suspensions after 3 months of settling.
At higher temperatures, layering formed after 3–4 days of undisturbed
settling. Two grams per liter kaolinite suspensions formed five distinct
layers; 8 g per 1., nine layers; and 16 g per 1. suspensions formed a
many-layered, banded structure after approximately 2 weeks.

If layered suspensions were cooled, the layers were not disturbed.
However, layering was very responsive to heating: they expanded and tilted
downward away from the heat source. With prolonged heating, layering
disappeared.

These experiments show that temperature and concentration markedly
affect long-term settling characteristics of fine-grained suspensions.
Layering forms most readily in water with relatively low viscosity and
density. If such layered suspensions were formed in nature, such features as
graded bedding, lamination, or varving probably would result after complete
settling.
Thermodynamics of the Various High Temperature Transformations of
Kaolinite
Authors: Schieltz N. C. , Soliman M. R.
Published: August 2006

Thermodynamic calculations of
ΔG for all possible transformations of
metakaolin at the temperature of the first DTA exothermic peak indicates
that the most stable transformation is the one that yields mullite rather
than γ-alumina.

The energy of crystallization of γ-alumina is
quite small—36,513 cal per mol, compared with the energy of crystallization
of mullite—336,180 cal per mol. Furthermore, the crystallization of
γ-alumina is very slow, and the crystal
growth never produces crystallite sizes much larger than the lower end of
the colloidal region. Hence, the gradual release of the small amounts of
energy liberated during the crystallization of
γ-alumina would be extremely difficult to detect
by DTA methods.