bluuebunny/crossref_metadata_2025 huggingface dataset:
Complex Viscosity of a Kaolin Clay
Authors: Franklin Arley G. , Krizek Raymond J.
Published: August 2006

The complex viscosity of a material is a two-component quantity, comprising real and imaginary parts. The real part of the complex viscosity is often very useful because in many materials it approaches the ordinary steady-flow viscosity at low frequencies. Because many materials with high viscosities are very slow in reaching a steady-flow condition, the determination of the steady-flow viscosity may be very difficult; however, an approximation can often be obtained from low-frequency values of the real part of the complex viscosity. In this study, the complex viscosity of a Georgia kaolin has been determined by measurements made on specimens subjected to oscillatory simple shear, over three decades of frequency. Other independent variables in the study are the water content of the clay and the shear strain amplitude. Data were obtained from experimental measurements in the form of values of the magnitude, or absolute value, of the complex viscosity, and the phase angle between the imposed oscillatory strain and the stress response. Empirical functional relationships are developed to relate these quantities to the independent variables, and these are in turn used to obtain the real and imaginary parts of the complex viscosity as functions of the independent variables. The results of this study indicate that the complex viscosity is not linear, but decreases approximately as a power function of the strain amplitude; the relation between the complex viscosity and the water content is approximately an inverse logarithmic one, and changes very rapidly at water contents near the liquid limit; and the phase angle increases with increasing strain amplitude approximately as a power function.
Abrasion pH, an Index of Chemical Weathering
Authors: Grant Willard H.
Published: August 2006

If a series of rock samples with granitic composition in various stages of chemical weathering is ground in a mortar with distilled water and the pH of the slurry produced is determined, it will be evident that the pH declines as the weathering increases. This relationship can be made useful by plotting abrasion pH against some other index of weathering such as the percentage of clay mineral or the bulk density of the weathered rock. Factors controlling abrasion pH are the cations such as K, Na, Ca, and Mg and the amount of clay mineral present.
Kinetics of Acid-Dissolution of Palygorskite (Attapulgite) and Sepiolite
Authors: Abdul-Latif Numan , Weaver Charles E.
Published: August 2006

Palygorskite and sepiolite were digested with large excesses of hydrochloric acid at constant temperature for various periods of time. The reaction was found to be of first order with respect to the magnesium, aluminum and iron components in the clay and also with respect to hydrochloric acid concentration.

The reaction rate constant for Mg is larger than for Fe, which is larger than for Al. Approximately one-third of the octahedral-type cations are extraneous, suggesting that only three of the five octahedral positions are filled. The reaction rate constant of Mg in sepiolite is about 240 times that for palygorskite. This may be an indication that sepiolite is less stable to chemical weathering than palygorskite.

The activation energies for Mg, Al and Fe in palygorskite were found to be the same and equal to about 18·4 kcal per mole.

Treatment of partially acid-digested palygorskite with magnesium ions under alkaline conditions resulted in an increase in the X-ray intensity of the 10·5 Å spacing, suggesting some of the palygorskite was reconstituted.
New Data for Tosudite
Authors: Shimoda Susumu
Published: August 2006

Tosudite from the Takatama mine is found as an alteration mineral of the wall rocks (tuff and tuffaceous sediments of Tertiary age) of gold-silver-quartz veins. A specimen free from impurities was obtained by the sedimentation method. Chemical composition: SiO2 42·14%; Al2O3 37·38%; Fe2O3 0·30%; MgO 0·08%; CaO 1·65%; Na2O 0·15%; K2O 1·40%; H2O+ 11·22%; H2O− 6·16%; total 100·48%. A negligible amount of MgO indicates that both octahedral sheets of the chlorite structure are dioctahedral. Structural formula is given as (K0.58 Na0.09 Ca0.57)(Mg0.04 Fe3+0.07 Al12.05) (Al2.28 Si13.72) O40.00(OH)20.008.88H2O.

A reflection at 30 Å with its higher order reflections and another reflection at 1·493 Å are observed. After heating at 300°C, a 27 Å phase has appeared, in which a single plane of water molecules was confirmed as the interlayer water of montmorillonite. The structures in air-dried state and in dehydrated steps were proved by comparing the calculated and observed F-values, and by Fourier synthesis. The DTA and TG curves and the i.r. absorption spectrum are reported in this paper.
Surface Area of Vermiculite with Nitrogen and Carbon Dioxide as Adsorbates
Authors: Thomas Josephus , Bohor Bruce F.
Published: August 2006

Surface-area studies were made on several homoionic vermiculites with both nitrogen and carbon dioxide as adsorbates. These studies show that only very slight penetration occurs between individual vermiculite platelets. This is in contrast to an earlier investigation of montmorillonite where it was found that the degree of penetration between layers is quite high, particularly for carbon dioxide, and is governed by the size and charge of the interlayer cation. The inability of these adsorbates to penetrate substantially between vermiculite platelets is due primarily to this mineral’s high surface-charge density.

The extent of penetration of nitrogen and carbon dioxide at the edges of vermiculite platelets, though slight, is influenced by the coordinated water retained within the sample at a given degassing temperature. Forces between layers are weakened with increasing water content, which permits slightly greater penetration by adsorbate gases. Thus, the surface area of vermiculite, as determined by gas adsorption, is larger than the calculated external surface area based upon particle size and shape considerations. In addition, “extra” surface is provided by the lifting and scrolling of terminal platelets. These morphological features are shown in scanning electron micrographs of a naturally occuring vermiculite.
Montmorillonite Deposits in Nevada
Authors: Papke Keith G.
Published: August 2006

Nevada has produced one-third million tons of montmorillonite clays; a major portion was natural adsorbent clay from the Ash Meadows district. Four properties, 3 with swelling and 1 with non-swelling montmorillonite, are currently producing.

Detailed geologic and laboratory studies were made of thirty Nevada montmorillonite deposits. Pyroclastic and other volcanic rocks, mainly Miocene and Pliocene in age, were the host for most of these. The montmorillonite deposits are believed to have been formed in four ways: (1) eleven deposits by alteration of volcanic ash shortly after it settled in lacustrine basins; (2) two deposits by deposition of fine-grained clastic materials; (3) eleven deposits by hydrothermal alteration of a variety of rock types near structural channelways; and (4) six deposits by partial leaching and alteration of glassy, rhyolitic volcanic rocks by ground water.

Montmorillonite is the predominant clay mineral in all the deposits except Ash Meadows, where saponite is present. Sodium is much more common as the exchangeable cation than calcium and/or magnesium. Kaolinite and illite are present in one-fifth of the samples; chlorite or mixed-layer material are rarely present. Quartz, cristobalite, feldspars, calcite, and gypsum are common impurities.

The tests performed on the clay samples were: color; texture; slaking reaction; percentage swelling in water; plastic viscosity, yield point and gel strength of clay-water slurry; colloid content; and pH. Some montmorillonites formed by incomplete alteration of pyroclastic rocks can be wet separated to yield a light-colored, — 2μ fraction with superior viscosity and thixotropy.
Multiple-Ion Diffusion—I. Techniques for Measuring and Calculating Apparent Self-Diffusion Coefficients in Heteroionic Systems
Authors: Brown D. A. , Dunn J. E. , Fuqua Ben
Published: August 2006

This investigation was designed to integrate the quick-freeze technique for ion diffusion with two computer programs to permit the simultaneous measurement and calculation of the diffus-ivity of a variable number of ions in heteroionic soil system. Kaolinite clay was prepared so as to have the following percentage saturations of the CEC, Sr2+65, Mg2+15, Rb+10, Na+5 and H+5. A quadruplicate radioisotope tag consisting of 85Sr, 28Mg, 86Rb, and 22Na was used to measure the diffusivity of each ion. The complex spectra were resolved by use of Schonfeld’s revised Alpha-M computer program. A probit-transformation procedure was formulated into a computer program to enable the calculation of each diffusion coefficient. These programs are described and illustrated with the diffusivity of 86Rb in kaolinite clay.
Chloritization of Montmorillonite by Its Coprecipitation with Magnesium Hydroxide
Authors: Gupta G. C. , Malik W. U.
Published: August 2006

A magnesium hydroxide-montmorillonite complex prepared at an OH/Mg molar ratio of 2 (16 meq Mg/g clay) and immediately cleaned of any free Mg(OH)2 behaves like magnesium-chlorite and shows no change during 3 months ageing. Magnesium hydroxide completely precipitates within the interlayer space of montmorillonite. X-ray diffraction analysis, thermal (DTA and TGA) studies, i.r. absorption analysis, polarographic reduction behaviour, and cation exchange capacity measurements confirm the transformation of montmorillonite to a chlorite-like structure. Further ageing of the complex results in the release of brucite from the interlayer space and expansion of the complex on glycerol treatment. X-ray analysis of the 6 months aged sample shows the presence of free brucite but not montmorillonite. A small but significant increase in CEC of the complex is observed on ageing. When the Mg(OH)2-montmorillonite complex is allowed to age in the presence of free Mg(OH)2 (external to montmorillonite unit layers) in a dry state, a “seeding” effect takes place and the “fixed” Mg(OH)2 starts coming out from the interlayer space after 10 days.
Analogues of Flint Clays in Soviet Literature
Authors: Chukhrov F. V.
Published: August 2006

The term “flint clay” used in USA and several other countries, corresponds very closely to the term “toasted bread (sukhar) clay”. In both USA and U.S.S.R., the typical occurences of “toasted clays” are confined to deposits of the lower Carboniferous. In their properties and occurrence the well-studied toasted clays of the Borovichy deposit (Novgorod province) are highly similar to the flint clays of Missouri, differing significantly only in having lower bulk specific gravity and higher porosity than do Missouri flint clays. Varieties with excess free alumina (diaspore, boehmite) are observed both among “toasted” and flint clays. The author suggests the term “toasted complex” (sukharnii kompleks) which corresponds to W. D. Keller’s term “flint clay facies”. The clays of the “toasted complex” are sediments of ancient swamps and lakes which contained rich vegetation. Their source material was finaly dispersed silicate particles transported from dry land. The structure and properties of toasted clays are explained by the precipitation of kaolinite as colloidal clumps in which crystallization occurred with formation of intimate intergrowths and variously oriented segregations.
Potassium and Cesium Ion Selectivity in Relation to Clay Mineral Structure
Authors: Sawhney B. L.
Published: August 2006

Selectivity of a number of vermiculites, montmorillonites and micas for K and Cs ions was determined by sorption of these ions from equilibrium solutions of diverse concentrations. The selectivity coefficients were related to the layer charge density and the area of the frayed edges in layer silicates.

Montmorillonites had the smallest selectivity for the two ions, while biotite and illite had the greatest selectivity. Selectivity of biotite and illite was limited to small concentrations of K, however. At greater concentrations the selectivity of vermiculite for K exceeded the selectivity of the micas.

The greater selectivity of vermiculites than montmorillonites for K and Cs ions was attributed to the greater layer charge density in vermiculites. The greater selectivity of micas than montmorillonites and vermiculites was attributed to the frayed edges of micas in addition to their larger layer charge density. As the frayed edges in illite were increased in area by removal of the interlayer K, the selectivity of illite for K also increased; thus confirming the selectivity of frayed edges for the K ions.
Titanium as Free Oxide and Substituted Forms in Kaolinites and other Soil Minerals
Authors: Dolcater D. L. , Syers J. K. , Jackson M. L.
Published: August 2006

Titanium in TiO2 minerals was differentiated from that isomorphously substituted into minerals by the use of dihydrogen hexafluorotitanate (hydrofluotitanic acid, H2TiF6), which selectively dissolved minerals containing substituted Ti4+, leaving free crystalline TiO2 minerals in the residue. Titanium analyses on the original samples and the residues remaining after H2TiF6 treatment, by both wet chemical (Tiron) and neutron activation methods, indicated that an average of 86 per cent of the titanium in seven kaolinite samples was present in the residual TiO2 form (largely anatase), whereas only 28 per cent in two bentonites was present in the TiO2 form. Residual Ti accounted for 100 per cent of the Ti in synthetic anatase and for 92 per cent of the Ti in coarse clay sized rutile, the latter value suggesting that about 8 per cent amorphous TiO2 was removed from the mechanically dry ground rutile by the H2TiF6 reagent. The Ti present as residual TiO2 in a variety of other samples ranged from 0 to 100 per cent.
pH Dependent Ion Exchange Properties of Soils and Clays from Mazama Pumice
Authors: Chichester F. W. , Harward M. E. , Youngberg C. T.
Published: August 2006

Cation exchange capacity (CEC) measurements were made for whole pumice soil samples by several methods, including standard procedures involving cation saturation, excess salt removal, and cation displacement steps, and a 45Ca2+ radioisotope dilution procedure. Results indicated that the vesicular pores of the pumice soil material affected attainment of ion diffusion equilibria, and, hence, introduced a large source of error in the measurements. On this basis, the validity of ion exchange values obtained for these soils was concluded to be subject to considerable doubt. More important, however, the solute and/or solution exclusion or retention exhibited by pumice particles during the course of CEC procedures was thought to be highly significant with respect to the probable influence exerted on physical, chemical, and biological properties of the soils in the field situation.

Interpretation of pH dependent cation and anion exchange capacity measurements of the <2μ clay fraction of the pumice soils was confounded by the occurrence of hydroxy interlayered 2: 1 phyllosilicate materials in admixture with the amorphous components. Since the interlayered materials contributed an indeterminate proportion of the total pH dependent charge of the mixture, it was further concluded that the measurement of this property was of little direct value in assessing the relative amounts of amorphous and crystalline components in the clay fractions of the soils investigated. However, the values obtained revealed fundamental aspects of ion exchange behavior which are important to understanding the complex systems involved.
Adsorption of Surfactants on Montmorillonite
Authors: Hower Wayne F.
Published: August 2006

Some authors have stated that anionic surfactants are not adsorbed by montmorillonite while others indicate very minor adsorption. Attempts to quantitatively determine the degree of adsorption have shown that certain problems exist which, unless recognized, will completely mask results. Some of these difficulties have been overcome but exact data have not yet been obtained. However, enough information has been gathered to prove that adsorption of anionic surfactants on montmorillonite is real and substantial. Reliable adsorption data for cationic and nonionic surfactants and one having both nonionic and anionic character have been obtained. It is indicated that 550 mg of these surfactants are adsorbed by 1 g of montmorillonite. X-ray diffraction data for complexes of all surfactants investigated confirm positive adsorption. However, the thickness of the adsorbed surfactant layers cannot always be quantitatively related to the amount of adsorbed surfactant.
Rectorite and the Rectorite-Like Layer Structures
Authors: Henderson G. V. , Bradley W. F.
Published: August 2006

Recurrent reports of analyses of X-ray diffraction data from regularly alternating and nearly regularly alternating structures like rectorite provide opportunity for a descriptive discussion of their nature. MacEwan-transform-based analyses have uniformly shown higher incidence of unlike adjacent layers than would be expected from random distribution.

The continuous Fourier transforms for pairs of 2: 1 layer silicate structures evaluated normal to the layers, provide a family of similar curves that are differently stretched out in reciprocal space for different assumed intervals between the two members of a pair.

For each exactly alternating example the relative amplitudes of the ordered reciprocal nodes distinguish the instances for which fixed interlayer populations are Na+ from those for which they are K+.

For sequences not exactly alternating scattering maxima are displaced from exact incremental positions in conformity with the Hendricks and Teller mixing functions, but relative intensities of adjacent observations still distinguish the alkali identities.
Burial Diagenesis in Gulf Coast Pelitic Sediments
Authors: Perry Ed , Hower John
Published: August 2006

Subsurface samples of shales ranging in age from Pleistocene to Eocene obtained from five Gulf Coast oil wells were examined mineralogically and chemically to determine the nature and extent of burial diagenesis in pelitic sediments. Illite/montmorillonite dominates the mineralogy and undergoes a monotonic decrease in expandability from about 80 to a limit of 20 per cent montmorillonite layers with increasing depth. The interstratification changes from random to ordered at about 35 per cent expanded layers. Discrete illite and kaolinite phases are ubiquitous and judged detrital. The discrete illite (mica) content of the whole rock decreases with depth, while the kaolinite shows no systematic variation. Chlorite occurs in appreciable amounts in only one well and there only in samples from the shallow water facies. This chlorite is also considered detrital.

Whole rock chemical analyses show no systematic variation with depth except for a decrease in calcium and magnesium caused by solution of carbonate. In contrast, potassium increases progressively with depth in the clay-size fraction, indicating a redistribution of potassium within the rock. Detrital illite (mica) seems to break down with increasing depth, thereby supplying potassium for interlayer fixation in illite/montmorillonite as the proportion of illite layers increases. The diagenetic reaction is independent of the geologic age of the sediments and of stratigraphic boundaries. Temperature seems to be more important than pressure in governing the reaction.
Effects of Potassium Removal on the b-Dimension of Phlogopite
Authors: Leonard R. A. , Weed S. B.
Published: August 2006

Potassium was removed from 5 to 20-μ size fractions of two phlogopites by treatment with sodium tetraphenylboron and replaced with various exchange ions. The b-dimension of the mica increased with K+ removal, which suggests that the K+ ion in phlogopite acts to constrain b. This being the case, the K—O bond in phlogopite must be lengthened and weakened relative to the K—O bond in dioctahedral micas.
The Origin of Pyrophyllite Rectorite in Shales of North Central Utah
Authors: Henderson G. V.
Published: August 2006

Pyrophyllite is widespread in pelitic rocks of the Manning Canyon Shale in north central Utah, and the association of this mineral with other clay minerals, especially rectorite is related to the origin. The regular mixed-layer clay mineral rectorite seems to form as a result of the alteration of muscovite-paragonite during late stages of diagenesis and represents an intermediate metastable phase in the mineral paragenetic sequence. Pyrophyllite subsequently formed from the alteration of rectorite during advancing metamorphism and is the stable end member of the clay mineral assemblage.

Structural interpretations of rectorite found in the Manning Canyon Shale shows a regular, alternating sequence which consists of a fixed layer of 9.6 Å and an expandable layer, varying from 10 Å to 17 Å. With ethylene glycol saturation in the natural state a basal reflection of 26.60 Å is recorded.
Precipitation of Kaolinite at 25°C and 1 ATM
Authors: Kittrick J. A.
Published: August 2006

The 0.2–5μ particle size fraction of montmorillonite from three sources was equilibrated with various solutions at room temperature. After 3–4 yr, kaolinite was found in some of the samples that were supersaturated with respect to kaolinite, but not in any of the undersaturated samples or in the original montmorillonite. X-ray diffraction analysis of the precipitated kaolinite showed no inter-layer expansion of glycerated, oriented samples. Random powder samples indicated a poor crystal-Unity. The thermal stability of the precipitated material was indistinguishable from that of crystalline kaolinite. The electron microscope did not reveal any distinctive sizes or shapes.

Equilibration behavior of several samples defined a single kaolinite solubility line at or above which kaolinite apparently begins to precipitate. The solubility line is equivalent to a standard free energy of formation (ΔG) of -904.2 kcal per mole of kaolinite. This represents highly crystalline kaolinite. The stability of kaolinite actually precipitated at room temperature probably depends upon precipitation conditions. Thus kaolinite stability could range from poorly crystalline up to the equivalent of the kaolinite solubility line at which initial precipitation begins.
Polytypism of Chlorite in Sedimentary Rocks
Authors: Hayes John B.
Published: August 2006

Four chlorite polytypes of Bailey and Brown (1962) have been identified by X-ray diffraction in clay-size chlorites of soils, sediments, and sedimentary rocks: (1) IIb, the polytype of common metamorphic and igneous chlorites; (2) Ib(ß = 90°); (3) Ib(ß = 97°); (4) Ia. An additional stacking arrangement. Iba, is defined herein as disordered chlorite which lacks an h0l diffraction band in the 2.4–2.5 Å region.

Most type-I chlorites are authigenic, as demonstrated by thin-section petrography. Type-I chlorites form during diagenesis, or less commonly during halmyrolysis, at temperatures and pressures less than those of low-grade metamorphism. A type-1 crystallization sequence is proposed, from least to most stable: Iba → Ib(ß = 97°) → Ib(ß = 90°). Conditions of low-grade metamorphism usually are necessary to cause conversion of Iba(ß = 90°) to IIb, the most stable and common polytype. Chemical composition has little or no influence upon polytype relative stabilities; temperature is much more important.

Sediment source areas with high relief, abundant rainfall, cold climate, and which contain IIb-chlorite-bearing metamorphic rocks, may yield essentially unweathered IIb chlorite to sites of deposition. Thus, clay-size IIb chlorite in unmetamorphosed sedimentary rocks can be interpreted as detrital. Caution is required, however, because IIb may be able to form authigenically at submetamor-phic temperatures, because it is the most stable polytype. Petrographic evidence is useful in such cases.

Chlorite polytypism as a geothermometer can be applied to several geologic problems: (1) the authigenic versus detrital origin of clay minerals in sedimentary rocks, particularly in graywacke matrix; (2) the recognition of diagenetic facies or gradients, areally and stratigraphically, within given geologic provinces; (3) the detection of hydrothermal and incipient metamorphic effects. Chlorite polytypism merits general application as an interpretive tool.
Globular Cluster Microstructure of Endellite (Hydrated Halloysite) from Bedford, Indiana
Authors: Diamond Sidney , Bloor James W.
Published: August 2006

Scanning electron microscope observation of endellite from Bedford, Indiana, discloses the existence of globular clusters of quasi-tubular endellite particles radiating from common centers. Individual clusters are of the order of 10 μ in overall diameter. The individual quasi-tubular particles are irregularly flattened in cross section, and some may be plugged at the ends. Conventional oven drying at 105°C results in partial unrolling and incomplete flattening of the quasi-tubular particles of some of the clusters. The globular cluster microstructure is taken to represent the result of in-situ crystallization from solution. If this is so, these hollow tubes cannot have arisen by the mechanism of repeated extrusion of concentric zonal crystallites as postulated by Chukhrov and Zvyagin.
Prototropy in Kaolinite during Percussive Grinding
Authors: Miller John G. , Oulton T. Dixon
Published: August 2006

When kaolinite undergoes percussive grinding, pronounced changes take place in its i.r. absorption spectrum even in the earliest stages of the grinding when the lattice is not yet destroyed. In this report, attention is directed to the change in the stretching bands of the hydroxyl ions. A remarkably rapid effect on the band of the intralayer hydroxyl ions has been observed and is attributed to a permanent removal of the protons from these ions. Auxiliary measurements of X-ray diffraction, thermal water loss, and DTA were used to corroborate the spectroscopic evidence for this ready prototropy.
Ion Selectivity by Weathered Micas as Determined by Electron Microprobe Analysis
Authors: le Roux J. , Rich C. I. , Ribbe P. H.
Published: August 2006

Electron probe micro-analysis studies on individual particles (40–60 mesh) of weathered micas treated with solutions containing equivalent amounts of Rb and Sr showed partial segregation of these elements. Rb was concentrated at particle and step edges, at cracks, and, in the case of partially K-depleted biotite, at boundaries of vermiculite and mica zones (“wedge zones”). The scarcity of wedge zones in mica from which nearly all of the K had been removed reduced the overall selectivity for Rb. The restricted exchange of interlayer Mg ions from vermiculite-like zones by a mixed Rb-Sr solution was observed in earlier studies with these micas. The proposed explanation for these results was a closing down of the interlayer space at the edge of the particle due to Rb concentration in these positions. This explanation is confirmed by the present study.
Interactions of Clay Minerals with Organic Polymers. Some Practical Applications
Authors: Theng B. K. G.
Published: August 2006

An account is given of the interactions between clay minerals and organic polymers with particular reference to their applications in agriculture, foundation engineering and industry.
The Nature of Clay Soils from the Mekong Delta, An Giang Province, South Vietnam
Authors: Post James L. , Sloane Richard L.
Published: August 2006

Soil samples from near Long Xuyen, South Vietnam, considered to be typical of the clayey alluvial soils of the Mekong Delta, were investigated to determine the soil mineral content and soil type. The soils are of fairly uniform composition, consisting mainly of clay minerals and quartz. the predominant clay minerals including illite and chlorite with lesser amounts of kaolinite and smectite. The small hydrous iron oxide content, indicated by fluorescence background intensity, verified that the soils are not latosols but are clayey estuarine soils amenable to future development as arable land.

The method of specimen preparation enabled direct quantitative analysis of the soil samples by X-ray diffraction with the aid of the results of mechanical analysis and of previous analyses of comparable soil samples from the Delta and nearby areas. A method for the quantitative determination of quartz was used that is independent of the powder crystallite orientation. A study of surface replicas of the soil samples by electron microscopy was made to illustrate the fabric of the soil. The undisturbed soil fabric consists mostly of somewhat randomly-oriented large domains of clay minerals with some blocky quartz particles. Nanno-fossils were present in all samples.
Optical and Electron Microscopic Investigation of Shear Induced Structures in Lightly Consolidated (Soft) and Heavily Consolidated (Hard) Kaolinite
Authors: Foster R. H. , De P. K.
Published: August 2006

A review of fabric studies of clays suggests the need for relating those fabric characteristics which are revealed at the two levels of magnification provided by optical and electron microscopy, and a technique to achieve this has been developed and is described within the context of the initial stages of a long term study of the interrelation between fabric and engineering behaviour. Two kaolinitic clays with contrived fabrics were prepared by controlling particle size, moisture content and pH of suspension, and consolidation load and were subjected to shear loading to failure. Resin impregnation techniques which permit the kaolinite to be cut into thin sections for transmission electron microscopy have been optimized with the object of minimizing fabric strain and damage during ultratomy.

The fabrics of the hard and soft ambient material are qualitatively compared by means of electron micrographs and are explained in terms of the preparatory procedures adopted for fabric control. The fabrics of the two types of shear induced structures are also qualitatively compared and explained in terms of the original fabrics and the subsequent shear loading.
Scanning Electron Microscopy of Clays and Clay Minerals
Authors: Bohor B. F. , Hughes Randall E.
Published: August 2006

The scanning electron microscope (SEM) proves to be ideally suited for studying the configuration, texture, and fabric of clay samples. Growth mechanics of crystalline units — interpenetration and interlocking of crystallites, crystal habits, twinning, helical growth, and topotaxis — also are uniquely revealed by the SEM.

Authigenic kaolins make up the bulk of the examples because their larger crystallite size, better crystallinity, and open texture make them more suited to examination by the SEM than most other clay mineral types.
I.R. Spectroscopic Evidence for Interaction Between Hydronium ions and Lattice OH Groups in Montmorillonite
Authors: Russell J. D. , Fraser A. R.
Published: August 2006

At low levels of hydration, exchangeable D+ in montmorillonite interacts with lattice OH groups and quantitatively converts AlMgOH groups to AlMgOD. Hydroxyl groups coordinated to two Al ions undergo a slower exchange, the extent of which is restricted by octahedral Fe3+ ions. The OH stretching vibration of AlMgOH groups in montmorillonite is assigned an unusually high frequency (3687 cm−1) compared with that of the same group in phengites (3602 cm−1).
Mechanisms Controlling the Permeability of Clays
Authors: Mesri Gholamreza , Olson Roy E.
Published: August 2006

Coefficients of permeability, calculated using Terzaghi’s theory of one-dimensional consolidation, are reported for smectite, illite, and kaolinite, in water, methyl and ethyl alcohol, benzene, and carbontetrachloride. When the pore fluid was water the clays were homoionized to either the sodium or calcium form and the pore water electrolyte concentration was varied. The coefficients of permeability are evaluated in terms of both mechanical and physico-chemical variables. It appears that the coefficients of permeability are mainly influenced by mechanical effects, particularly the distribution of void sizes and the tortuosity of the channels. The coefficient of permeability is maximized if the flow channels consist of many small channels and a relatively few large ones, through which the main flow occurs. Physico-chemical variables exert great influence on the coefficient of permeability through their influence on dispersion or aggregation of the clay particles.
Structural Factors Controlling Stacking Sequences in Dioctahedral Micas
Authors: Güven Necip
Published: August 2006

Deviations in the symmetry of mica single layers from the ideal arrangement with all atoms in hexagonal arrays are caused by the structural factors such as compositional variation (substitutions), order-disorder, and distortions. The derivative crystal structure theory as applied to mica polymorphism, implies that the ideal symmetry of the mica single layer (C2/m) can be altered to one of its standard subgroups by these structural factors. The “derivative structure” of the single layer may allow a unique interlayer and a specific intralayer configuration and result in a regular stacking sequence.
Erratum to: Scanning electron microscopy of clays and clay minerals
Authors: Bohor B. F. , Hughes R. E.
Published: August 2006

The author regrets that in the photograph section on p. 50 the caption to the “top” Fig. 2 should read:

Fig. 2(b). Rock sample of attapulgite from Yucatan, Mexico (Tertiary).

the caption on the “bottom” Fig. 2 should read:

Fig. 2(a). Spray-dried attapulgite from Yucatan, Mexico.

Also the bar scales on Fig. 9 were inadvertently juxtapositioned:

Fig. 9(a) should carry the 10 μL scale, and Fig. 9(b) the 1 μ scale.
Dodecylammonium-Mica Complexes—I Factors Affecting the Exchange Reaction
Authors: Mackintosh E. E. , Lewis D. G. , Greenland D. J.
Published: August 2006

Dodecylammonium chloride (DAC) is used as a reagent to displace potassium from a wide range of mica minerals. Displacement is rapid and essentially complete for trioctahedral micas even in dilute solutions (0·02N DAC) at low suspension concentrations. Increasing the suspension concentration, or the concentration of potassium in the extracting solution decreased the extent to which potassium could be displaced before equilibrium was established. Under standardized conditions of temperature and suspension concentration, the rate of potassium displacement increased as the particle size decreased although complete displacement was more difficult to achieve for the finest fraction (< 2μ) than for the coarser particles.

The trioctahedral samples were shown to be more susceptible to potassium depletion by DAC than dioctahedral material. Within the range of trioctahedral samples examined the rate of reaction was found to be closely related to the fluorine content of the sample. Data obtained for the more resistant dioctahedral specimens was not sufficiently detailed to enable any similar relation to be established.
Transformation of Sericite into an Interstratified Mineral
Authors: Tomita Katsutoshi , Sudo Toshio
Published: August 2006

Sericite was K-depleted with molten LiNO3. The sample was changed into an interstratified structure in the presence of a small amount of LiNO3 after prolonged treatment, and in the presence of a considerable amount of LiNO3 a similar structure was formed after about 3 hr of reaction. In the case of the presence of the proper amount of NaCl, a mixed-layer structure was easily obtained by treatment for a long period of time with a considerable amount of molten LiNO3.

The interstratified mineral had a basal spacing of 22 Å–23·3 Å which was expanded to 25 Å–27·6 Å by treatment with ethylene glycol.
Particle Geometry and Optical Density of Clay Suspensions
Authors: Lahav N.
Published: August 2006

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.
Surface Charge Characterization of Layer Silicates by Competitive Adsorption of Two Organic Divalent Cations
Authors: Philen O. D. , Weed S. B. , Weber J. B.
Published: August 2006

Diquat2+ (1, 1’-ethylene-2, 2’-dipyridinium ion) and paraquat2+ (1, 1’-dimethyl-4, 4’-di-pyridinium ion) were competitively adsorbed by Na-saturated kaolinites, smectites and expanded and collapsed vermiculites. The relative preference for one or the other cation varied with the surface charge densities of the adsorbents and the location of the adsorption site, i.e. internal or external. Minerals with high surface charge exhibited preference for diquat whereas minerals with low surface charge preferred paraquat. Expanded vermiculites preferentially adsorbed diquat on internal surfaces. Collapsed vermiculites generally showed a preference for paraquat. Smectites and kaolinites preferentially adsorbed paraquat.

Surface charge densities of the layer silicates vs. the relative preference for diquat revealed two linear relationships, one for internal adsorption and one for external adsorption. Internal adsorption was characterized by a strong preference for paraquat on low-charged smectites, a relative decreasing preference for paraquat with higher-charged smectites, and a strong preference for diquat on high-charged expanded vermiculites.

Preferential adsorption for paraquat by kaolinite was quite similar to adsorption of paraquat on the external sites of vermiculites. There was no apparent relationship between competitive adsorption and surface charge density of kaolinite.
Sodium-Lithium Exchange Equilibria on Vermiculite at 25° and 50°C
Authors: Gast R. G. , Klobe W. D.
Published: August 2006

Sodium-lithium exchange equilibria between dilute aqueous chloride solutions and 0.2–62 μ Transvaal, South African vermiculite were studied at 25° and 50°C using a dialysis technique. The K content of the vermiculite was reduced to < 1% of the exchange capacity of 2·14 me/g by exhaustive extraction using Na-tetraphenylboron. The thermodynamic equilibrium constants and in turn the standard free energies and heats of exchange were evaluated from the equilibrium selectivity coefficients at the two temperatures. The standard entropy of exchange, ΔS°, was calculated according to the relationship ΔG° = ΔH° − TΔS°. Similar results were obtained for Na → Li and Li → Na exchange at 25°C, thus confirming the reversibility of the reaction.

Sodium preference increased with Na saturation of the vermiculite and equilibrium selectivity coefficients ranged from 6·0 to 22·0 at 25°C. In comparison, selectivity coefficients for Na-Li exchange on montmorillonite ranged from 1·0 to 2·0 and became smaller with increasing Na saturation. The standard free energy and heat of exchange on vermiculite at 25°C were −1444 and −5525 cal mole−1, respectively, resulting in a ΔS° value of −13·7 e.u. This relatively large entropy change is probably due to differences in ion hydration in the solution and surface phases.
Reactivity of Clay Minerals With Acids and Alkalies
Authors: Carroll Dorothy , Starkey Harry C.
Published: August 2006

One-g samples of a montmorillonite, a metabentonite, an illite, two kaolinites, and three halloysites were treated with 50 ml of hydrochloric acid (6·45 N, 1: 1), acetic acid (4·5 N, 1: 3), sodium hydroxide (2·8N), sodium chloride solution (pH 6·10; Na = 35‰; Cl = 21·5‰), and natural sea water (pH 7·85; Na = 35·5‰; Cl = 21·5‰) for a 10-day period in stoppered plastic vials. The supernatant solutions were removed from the clay minerals and analyzed for SiO2, Al2O3, CaO, MgO, Na2O, and K2O. All the solutions removed some SiO2, Al2O3, and Fe2O3 from the samples, but the quantities were small. Sodium hydroxide attacked the kaolin group minerals more strongly than it did montmorillonite, metabentonite, or illite. Halloysite was more strongly attacked by hydrochloric acid than was any of the other experimental minerals. Hydrochloric acid removed iron oxide coatings from soil clay minerals, but acetic acid did not remove them completely. The samples most strongly attacked by HCl and NaOH were examined by X-ray diffraction. Acid treatment did not destroy the structure of the clays, but the halloysite structure was partially destroyed. Sodium hydroxide attacked the halloysite structure, as shown by chemical analysis and X-ray diffraction. These experiments show that treatment in dilute acids has no harmful effect in the preparation of clays for X-ray diffraction. Acetic acid is preferred to hydrochloric acid for this purpose. Hydrochloric acid cleans clay minerals by removing free iron oxide from the surface; acetic acid is less effective.
Clay Mineral Formation In A Deeply Weathered Boulder Conglomerate In North-East Scotland
Authors: Wilson M. J. , Bain D. C. , McHardy W. J.
Published: August 2006

The clay minerals formed in a deeply weathered boulder conglomerate of Middle Old Red Sandstone (Devonian) age in north-east Scotland have been studied by a variety of physical and chemical techniques. The granite and granulite boulders in this deposit are completely weathered. With the exception of microcline, all the feldspars in these rocks—orthoclase feldspar, orthoclase-microperthite, albite, and oligoclase—weather to a Cheto-type montmorillonite, poor in iron. Electron and optical microscopy indicate that the weathering transformation is a direct one, without the intervention of any intermediate crystalline or well-defined amorphous phase. Structural control of the primary mineral over the formation of the montmorillonite seems to have been a minimal factor and the evidence suggests that the clay mineral crystallized from the soluble or colloidal products arising from the decomposed feldspars. Smaller amounts of kaolinite also formed during weathering but largely from the weathering of muscovite. The environment in which these changes occurred seems to have been alkaline in a relatively closed system. Chemical analyses of related cores and weathered shells of granite and granulite bounders show only a slight decrease of silica and an increase in magnesia. Judging from the extent of alteration to secondary clay minerals, the order of resistance towards weathering of the primary minerals in these rocks is plagioclase = orthoclase < muscovite < biotite < microcline < quartz.
Fabric of Kaolinite and Illite Floccules
Authors: O’Brien Neal R.
Published: August 2006

A scanning and high voltage electron microscope study of the fabric of laboratory sedimented moist uncompressed kaolinite and illite floccules reveals an abundance of face-face flake orientation in the porous clay network. Clays were flocculated in the laboratory in both distilled water and slightly saline (1 g/l. NaCl) water using various clay concentrations. Floccules taken from the moist clay mass were prepared for study by freeze-drying and impregnation with polyethylene glycol.

There is little difference in the fabric of kaolinite flocculated in distilled or slightly saline water. The fabric is dominated by a 3-dimensional network of twisted chains of face-face oriented flakes having the appearance of a stair-stepped cardhouse. Illite floccules in distilled water also consist of abundant face-face oriented overlapping flakes. However, in salt water there is a more even mixture of fabrics—edge-to-face flocculation of individual platelets and also stepped clusters of face-to-face oriented flakes, the latter being more abundant.

It is suggested that under the experimental conditions the double layer of each clay particle is compressed resulting in an increase in the importance of van der Waals forces of attraction. As a result flakes approach each other and rotate into a parallel or subparallel position. The resultant dominant fabric is that of a stepped cluster of overlapping flakes.
Clay Mineral Formation in an Alpine Environment
Authors: Reynolds Robert C.
Published: August 2006

Vermiculite, mixed-layer vermiculite-phlogopite, and smectite are presently forming from igneous and metamorphic bedrock in the alpine zone of the northern Cascades, Washington. In addition, south-facing exposures of quartz-diorites and metadiorites above snow line are weathering to ferruginous bauxite. Calculations indicate that vermiculite is presently forming from phlogopite schists in this environment at a unit area rate that is approximately six times the average estimated rate of clay erosion for North America. The mineralogical data indicate that chemical weathering in this region is a quantitatively significant process, and suggest that in the development of current geomorphic concepts researchers may have generally underestimated the importance of chemical weathering in alpine environments.
Mechanisms of Formation of Colored Clay-Organic Complexes. A Review
Authors: Theng B. K. G.
Published: August 2006

The interactions of clay minerals with organic compounds which give rise to the formation of colored complexes, are discussed. The color reactions of clays can be ascribed to a charge transfer between the mineral and the adsorbed species. The active sites on the clay are aluminums exposed at crystal edges and/or transition metal cations in the higher valency state at planar surfaces both of which can act as electron acceptors. The pH of the system, the nature of the solvent and that of the exchangeable cation, influence the rate of color development and the final intensity and quality of the color produced. Steric factors also play a part in reactions involving bulky organics. Some practical applications based on color reactions of clays with electron-donating organic substances are described.
Acid Character of Sauconite: Increase in Cation Exchange Capacity on Aging in Water and the Role of Zn2+ and Al3+ Ions
Authors: Mitra R. P. , Sindhu P. S.
Published: August 2006

pH- and conductometric titration curves of acid sauconite, freshly prepared by the action of H-resin on sauconite showed four segments, each, where H+, Al3+ and Zn2+ ions and a weak acid reacted with the added base in the sequence mentioned. The H+, Al3+ and Zn2+ ions, but not the weak acid, could be exchanged for the cations of a neutral salt. The exchangeable Al3+ and Zn2+ ions were derived from the lateral surfaces by the action of the H-resin. When the acid sauconite was allowed to age in water, the exchangeable H+ and Al3+ ions were gradually replaced by Zn2+ ions giving, finally, a Zn-clay. The pH rose from 4·2 to 6·3 and the total amount of exchangeable cations increased as aging proceeded. When the Zn-clay was formed, the increase in cation exchange capacity was about 70 per cent. Octahedral Al at the edges, carrying positive charges, were discharged by hydrolysis during the aging, causing the net negative charge and, hence, cation exchange capacity, to increase. Aging had little effect on the amount of the weak acid. Zn and Al ions at the edges exhibited the weak acid function. Only edge-Zn was active in the fully aged clay.