bluuebunny/crossref_metadata_2025 huggingface dataset:
The infrared spectrum of water adsorbed on hectorite
Authors: Prost R. , Chaussidon J.
Published: December 2006

The infrared spectrum of water adsorbed on K-hectorite has been studied in the frequency range 2600–4000 cm−1 on samples equilibrated with relative humidities of 0% to 100%. The model proposed by J. Mamy for the molecular array of water upon the mineral surface has been used as a starting assumption. A ‘unit cell’ made of two H2O molecules is then considered as a possible theoretical basis for the interpretation of the infrared spectrum. When taking into account this unit cell six stretching frequencies may be anticipated. The six components of the OH stretching band are clearly resolved at −95°C at room temperature a Curve Resolver was used to analyse the composite band, which was recorded at various incident angles (0–45°). From the variation of the integrated absorption of each component band given by the curve resolver, the orientation of the dipolar moment is calculated, and compared with the theoretical one deduced from the model.
Separation of illite and chlorite in clays by electromagnetic techniques
Authors: Berry Richard , Jørgensen Per
Published: December 2006

Two types of cells for magnetic separation of clay minerals in aqueous suspension, were designed. The ceils can be used with a standard Franz Isodynamic Separator. The technique reported is effective in separating chlorite from a natural clay mixture.
The adsorption of aliphatic alcohols by montmorillonite and kaolinite
Authors: German W. L. , Harding D. A.
Published: December 2006

Adsorption isotherms for an homologous series of primary aliphatic alcohols from aqueous solution by montmorillonite and kaolinite saturated with either sodium or calcium ions have been determined. The results show that adsorption is a function of chain length and exchangeable cation in the case of the more insoluble alcohols. Exchangeable cation does not affect the adsorption of the soluble alcohols to any significant extent. Adsorption of the longer chain alcohols occurs in voids in the mineral aggregates.
Selective Dissolution and Differential Infrared Spectroscopy for Characterization of 'Amorphous' Constituents in Soil Clays
Authors: Wada K. , Greenland D. J.
Published: December 2006

Poorly crystalline inorganic materials were removed from soil clays of different origin and mineral composition by successive treatments with sodium dithionite, 2 % Na2CO3 and 0·5 N NaOH. Techniques are described whereby difference spectra representing the infrared absorption of the materials removed by the treatments can be obtained. These spectra indicate that the materials dissolved are related to the mineral composition of the soil clay. Dissolution of allophanes of different composition was only proved for two volcanic ash soil clays in which these dominated. Layer silicates, probably including kaolin, were dissolved from the clay fractions of the red-brown earth and krasnozem studied. In addition, alumina-rich gel-like material and gibbsite, but no allophanes, were dissolved from another volcanic ash soil clay in which gibbsite and layer silicates are present in considerable amounts.
The Role of Sorptive Layers in the Formation And Change of the Crystal Structure of Montmorillonite
Authors: Eirish M. V. , Tret'Yakova L. I.
Published: December 2006

The influence of sorbed cations and hydration on the a and b dimensions of montmorillonite, has been established by the selected area diffraction technique (S.A.D.) and by X-ray diffraction analysis. Concepts on the bonds and interaction mechanism of aluminosilicate layers with sorbed cations and water molecules (which form hydrate-ionic layers) are discussed. These concepts also indicate the basic stages of the sorption process and the formation of the montmorillonite structure. Assuming that aluminosilicate and hydrate-ionic layers represent a single crystal-chemical structure, the change of configuration of the aluminosilicate layers and dimensions of the montmorillonite lattice are explained.
Cation Exchange Properties of Micas
Authors: Newman A. C. D.
Published: December 2006

The sorption of potassium by mica partially depleted of potassium was studied by adding potassium to a solution of sodium chloride in quasi-equilibrium with the mica. The concentration of potassium in the solution was increased 1·5 times before reverse exchange was initiated. Potassium resorbed by the depleted mica was extracted more readily than potassium from the original mica. Potassium exchange from mica is not reversible; there is irreversible change in the mica when potassium is exchanged and also an additional hysteresis in the forward and reverse exchange.
Cation Exchange Properties of Micas
Authors: Brown G. , Newman A. C. D.
Published: December 2006

Two phlogopites depleted of potassium by extraction with sodium tetraphenyl boron released resorbed potassium more readily than the original micas, but the large difference in the exchange parameters of the two micas were paralleled by those of their potassium-saturated alteration products. The apparent basal spacings of the potassium-saturated alteration products were about 0·03Å larger than those of the corresponding untreated micas; their broader lines indicate structural irregularities.
An Assessment of some Thermal and Chemical Techniques used in the Study of the Poorly-Ordered Aluminosilicates in Soil Clays
Authors: Bracewell J. M. , Campbell A. S. , Mitchell B. D.
Published: December 2006

The usefulness of various techniques for characterizing poorlyordered inorganic gel systems in clays is considered. Many established instrumental techniques are unsuitable, but thermal methods, chemical dissolution techniques, and specific surface reactions are more appropriate. The reaction of fluoride with clays is used as an example of the latter and methods for detection and monitoring of the fluoride uptake are described. Its value is demonstrated for studying gel materials in soils and relating them to synthetic alumina-silica gels.
Hydroxyl Stretching Bands in Micas: A Quantitative Interpretation
Authors: Rouxhet Paul G.
Published: December 2006

Methods are described for estimating a valuable absorption coefficient for OH stretching bands of micas: the integrated parallel absorption coefficient K.

From a correlation between this coefficient and the OH content of biotites and phlogopites, it was found that the parallel absorption coefficient per hydroxyl group in these trioctahedral micas is not appreciably influenced by the chemical composition and the direction of the OH bond. A clear deviation was observed for the low frequency band of a biotite characterized by a well-ordered orientation distribution for the corresponding hydroxyl groups.

The integrated parallel absorption coefficient of muscovite is proportionally 2·5 to 3 times larger than that of trioctahedral micas.
The Formation of Stable Sols from Laponite, A Synthetic Hectorite-Like Clay
Authors: Neumann B. S. , Sansom K. G.
Published: December 2006

The effects of simultaneous additions of electrolyte and peptiser to dispersions of the synthetic hectorite-like clay, Laponite, have been studied. It has been unexpectedly discovered that whereas many cations cause gelling and flocculation of the dispersions as expected by colloid chemical theory, some cations actually stabilize the sols obtained with peptiser. A relationship has been found between the effectiveness of the cations in increasing sol stability and their size and charge.

The effects of time, temperature and peptiser concentration have also been examined, and explanations are offered for the phenomena observed.
Optical Properties of Organic Complexes of Montmorillonite
Authors: Greene-Kelly R.
Published: December 2006

The optical properties of oriented montmorillonite aggregates were measured in both non-complexing and complexing media. The changes observed lead to the following conclusions. Preparing oriented aggregates of clays for optical examination requires considerable care to avoid spurious orientation effects. In determining the optical constants of montmorillonite aggregates the medium must wet and enter the aggregate readily and displace the air, particularly from the smaller pores, otherwise large form birefringence effects of uncertain magnitude will occur. A suitable medium is likely to be one that complexes montmorillonite. The complex it forms must have relatively isotropic interlamellar layers and this is more likely with isodimensional molecules. Consideration of complexes with simple compounds suggests that the intrinsic birefringence of aggregates is overestimated by conventional techniques.

Forming complexes with aromatic compounds usually results in the birefringence of the aggregate being essentially determined by the orientation and anisotropy of the intercalated molecules.
The Interaction of Kaolinite with Polyphosphate and Polyacrylate in Aqueous Solutions—Some Preliminary Results
Authors: Bidwell J. I. , Jepson W. B. , Toms G. L.
Published: December 2006

The choice of kaolinite sample for surface chemical studies is examined. An adsorption apparatus, particularly suited for those studies where the adsorbate acts as a deflocculant, is described. Some preliminary results are given for the adsorption of total phosphate from tetrasodium pyrophosphate solutions and of polyacrylate from sodium polyacrylate solutions. The release of aluminium and silicon from the kaolinite was measured; with tetrasodium pyrophosphate, aluminium-phosphate complexes are formed.

Competitive adsorption measurements suggest that the polyacrylate is adsorbed on the positively charged edges of the kaolinite.
Dickite from Job's Hill St Mary, Jamaica
Authors: Davis C. E. , Thompson B. E. , Taylor W. A. , Holdridge D. A.
Published: December 2006

Examination of rock samples from Job's Hill, St Mary, Jamaica, by chemical, X-ray, differential thermal, and infrared analyses showed predominant dickite with associated nacrite and kaolinite. The uniqueness of this deposit makes it possible that selected material could be used as a standard mineral.
The Differential Thermal Analysis of Flocculated Clay Samples
Authors: Dollimore D. , Heal G. R. , Horridge T. A.
Published: December 2006

Clays may be flocculated from suspension by various polymeric flocculating agents. In this study the technique of differential thermal analysis is used to identify the flocculating agent and to study its behaviour when adsorbed on the clay particles. It is shown that the clay particles display normal properties on sedimenting in the presence of sufficient polymer to cause flocculation. The differential thermal analysis trace for clays is only affected when the flocculating agent is present on the surface in quantities in excess of that required for effective sedimentation.
On the characterization of ceramic clays
Authors: Cole W. F. , Lancucki C. J. , Powell D. A.
Published: December 2006

Ceramic clays are characterized by a method that stems from the IL/MA procedure proposed by Keeling (1958a, b) but which is more rapid to perform and more basic in concept. By thermogravimetric methods an estimate is made of both OH water and interlayer plus physically adsorbed water. These are plotted against each other in a manner similar to the IL/MA plot. The composition of the clay can be characterized uniquely on such a diagram by estimating either the quartz or the free silica contents of a sample, its silt, and < 2μ fraction, and plotting for each on a 100% clay basis their OH water, and interlayer and physically adsorbed water. Simple methods are given for assessing these factors. The determination of interlayer water content could form the basis of a method of plant control of clay composition in a way similar to that proposed by Keeling using moisture adsorption determinations.
Bentonitic beidellite-mudstone from the Faeroe Islands
Authors: Sabine P. A.
Published: December 2006

A Tertiary mudstone from beneath worked coal among the basalts of the Faeroe Islands is mainly composed of aluminium-rich dioctahedral smectite, disordered kaolinite (amounting to about one quarter of the smectite) and probably about 13 ~ amorphous material. The texture is the result of crystallization in place. Chemical analysis suggests an ionic formula for the smectite of (Ca0.32Na0.10K0.04) (A13.88 Fe0.06+3Fe0.05+2Mg0.29) (Si6.71 A11.29) O20 (OH)4· 3·0 H20, which corresponds closely to beidellite. The total charge on the interlayer cations is 0·78 and cationexchange capacity is 52·5 meq/100g. DTA curves yielded endothermic peaks at 140°C, 220°C, and 555°C with an exothermic peak at 955°C. The nomenclature is discussed and the material considered to be a bentonitic beidellite-mudstone; the rock, which has crystallized in place has similarities with tonstein in its mode of formation.
Two mixed-layer mica-montmorillonite minerals from sedimentary rocks
Authors: Gilkes R. J. , Hodson F.
Published: December 2006

Two clay deposits, the Stafford Clay marker bed from the Middle Coal Measures of North Staffordshire and the Woolhope Bentonite from the Silurian, Woolhope Limestone near Woolhope in Herefordshire are described. These clays contain mixed-layer clay minerals which have been separated by sedimentation for mineralogical and chemical analysis. Both minerals are shown to be mica-montmorillonites with MacEwan stacking parameters PA= 0·59, PAA= 0·44 and PA= 0·56, PAA= 0·70 respectively. In both cases the average layer charge (1·22 and 1·46) is intermediate between that of montmorillonites and micas but the exchangeable cation layer charge (1·07 and 1·27/montmorillonite layer) and fixed cation layer charge (1·32 and 1·63/mica layer) of the component layers are higher and lower respectively than the normal range of montmorillonites and micas. Some chemical data are given for the raw material which yielded these minerals and for associated and related rocks. In particular K, U and Th determinations permit a discussion of the natural gamma-ray flux which is sufficiently more intense than that of the associ~.ted sediments to permit its detection by scintillation counter in the field.
Primary aliphatic alcohol-homoionic montmorillonite interactions
Authors: German W. L. , Harding D. A.
Published: December 2006

Complexes formed by straight chain, primary, aliphatic alcohols from methanol to n-decanol with Ca- and Na-montmorillonite from the liquid and vapour phases, have been investigated by X-ray techniques. Satisfactory complexes are formed more readily by the Ca-mineral and from the liquid phase rather than from the vapour phase. Molecular configurations of the adsorbed molecules are suggested consistent with the experimental data. The importance of cation-dipole interactions for the lower members of the series is stressed.
Mineralogical studies of a species of stevensite from the Obori mine, Yamagata Prefecture, Japan
Authors: Shimoda Susumu
Published: December 2006

A variety of stevensite was collected at the Obori mine, Yamagata Prefecture, Japan. Analysis shows close agreement with published data for stevensite. Chemical composition: SiO2 52·76%; A1203 trace; Fe203 0·38%; MgO 23·67%; MnO 1·57%; CaO 2·19%; Na2O 0·37%; K2O 0·00%; H2O+ 6·52%; H2O− 12·38%; Total 99·84%. The structural formula is (Fe0·04 Mg5·31 Mn0·02) Si80·1 020·00 (OH)4·00·Ca0·36, Na0·10.

This specimen shows an interstratified structure of dehydrated and hydrated layers, the former caused by dehydration of the interlayer water, although stevensite essentially contains a non-swelling layer and shows interstratification. The intensities and spacings of the 00l reflections change successively with changes in humidity. When treated with water and glycerol, the 00l reflections are similar to those of montmorillonite. The DTA and TG curves are similar to those of stevensite and an interstratified mineral of talc and saponite.
Gélification de vermiculite dans des solutions d'acideγ-aminobutyrique
Authors: Rausell-Colom J. A. , Salvador P. S.
Published: December 2006

Vermiculite single crystals swell to the gel state as a consequence of treatment with concentrated solutions ofγ-aminobutyric acid.

The amount of swelling was determined, by measuring by X-ray diffraction the separation of the elementary silicate layers in the gel-like crystals.

By application of pressures into the gels along the swelling direction, a direct measure of the swelling pressure is obtained. The relation between swelling pressures and equilibrium interlayer distances is a function of both cationic concentration and dielectric constant of the solution. Measured swelling pressures are consistent with a model based on formation and interaction of diffusedouble layersof aminoacid cations around the silicate particles, these having a Stern layer of an approximate thickness of 5 Å. The specific chemical adsorption potential of the system has been estimated asφ= 3·3 + 0·2 Kcal/mol.
The neoformation of clay minerals in brackish and marine environments
Authors: Jeans C. V.
Published: December 2006

It is suggested (1) that large amounts of Al, Fe and Si carried in solution by fresh water are chemically precipitated as hydroxide gels in the brackish water environment of estuaries and deltas, and (2) that these gels are subsequently deposited in both the brackish water environment and in the neighbouring seas, where they become parental material for the neoformation of clay minerals, and various other silicate and iron minerals. The types of neoformed minerals will depend upon both the composition of the parental gels and the physico-chemical milieu of their crystallization. Evidence is discussed supporting this hypothesis from the following sources (1) the concentrations of Al, Fe and Si dissolved in fresh water and in sea-water, (2) experimental work on the crystallization of alumino-siliceous gels, and (3) a study of the precipitation of Si from the waters of the Mississippi River delta.

Because of the unusual sediment pattern of present times, this source of neoformed clay minerals and other minerals contributes only a small proportion of the sediments of the brackish parts of estuaries, deltas and the adjacent seas, which are dominated by fine-grained continental detritus. In earlier geological eras, when the world's river systems carried only relatively minor amounts of fine-grained continental detritus, this source of neoformed minerals is likely to have contributed a considerable proportion of the fine-grained sediments of these areas of sedimentation. Three possible examples are discussed.
Hydrothermal and dry-heat fixation of K by soil clays and the effects on C.E.C., surface area and mineralogy
Authors: Davis C. E. , Ahmad N. , Jones R. L.
Published: December 2006

Fixation of K by soil clays and selected reference clay minerals was induced by dry heat and hydrothermal procedures, at 100°C, 200°C and 380°C. Appreciable amounts were fixed at all temperatures. In the cases of the samples treated hydrothermally the amounts fixed increased with pressure.

Fixation by dry heating at 380°C was significantly greater than at 100°C and 200°C respectively. Fixation under hydrothermal conditions increased in order 380°C > 200°C > 100°C.

Reductions in cation exchange capacities (and surface areas) were associated with fixation, indicating that some fixation was due to ion exchange. Changes in mineralogy in some of the samples also support the conclusion that ion exchange was partly responsible for fixation. Some of the fixation under hydrothermal conditions was due to the formation of insoluble K-compounds - as for example the synthesis of a new mineral when one sample was treated.

The lattice-iron content of the clays may have influenced their hydrothermal behaviour. Thus the Princes Town Clay ( > 7-5 % lattice-iron) and three nontronites (≫ 7-5 % lattice-iron) showed appreciable lattice collapse after hydrothermal treatment, while Wyoming bentonite and hectorite (<3-5%) lattice-iron) showed no collapse at all.

The degree of crystallinity of the mineral may also have influenced its hydrothermal reaction. For example, the highly disordered soil kaolinite (St John's) was much more reactive than the more ordered Georgia kaolinite. Also, the more-ordered reference clays fixed relatively less K at 380°C than the less-ordered soil clays.
Studies on the interaction of cationic surfactants with clay minerals
Authors: Malik W. U. , Srivastava S. K. , Gupta Devendra
Published: December 2006

Adsorption and desorption of cationic surfactants, cetyl pyridinium bromide, cetyl trimethyl ammonium bromide, dodecyl pyridinium bromide on bentonite, kaolinite and illite, and their diffusion through a bentonite membrane have been studied.

The binding of these compounds on the mineral surface takes place much beyond the exchange capacity. For excessive saturations with long chain compounds like these, the chains stand erect to the surface. A correlation of area per exchange site and area associated with surfactant molecule on clay surface also supports this view. The increase in the extent of adsorption with the size of the organic cation is due to an increase in the van der Waal's forces between clay and surfactant molecule. Isosteric heats of adsorption at different stages of surface covered with surfactant have also been determined and the same was found to pass through a minimum point. Larger ions desorb less, owing to the lesser solubility and larger contribution of dispersion forces.

Permeability of these surfactants and energy of activation of the diffusion process through the H- bentonite membrane has also been investigated. Diffusion of these cations takes place via exchange positions through the membrane and the order is exactly the reverse of their adsorption on the clay surface.
Weathering of micaceous clays in some Norwegian podzols
Authors: Kapoor B. S.
Published: December 2006

A study of the weathering of micaceous clays in some Norwegian podzols, includes semiquantitative estimates of minerals in the concentrated clay fractions which show a decrease in the amounts of illite and chlorite, and an increase in vermiculite and mixed-layer minerals upward in the profile. Illite, the dominant mineral at depth, weathers to hydrobiotite in the surface horizon of the profile. Subsequent weathering of hydrobiotite in this portion of the profile produces trioctahedral vermiculite and smectite, or intergrade smectite-chlorite.
A simple diffractometer heating stage
Authors: Brown G. , Edwards B. , Ormerod E. C. , Weir A. H.
Published: December 2006

The construction is described of a heating stage for examining oriented clay specimens in a Philips' diffractometer. The stage, which is simple and cheap to make, is interchangeable with standard specimen holders, operates over the range 20—265°C and does not require the diffractometer to be specially modified. The maximum temperature attained at the surface of the specimen collapses freely-expanding Mgsaturatcd vermiculite and prevents re-expansion of layer silicate minerals once they have been collapsed.
Acid character of nontronite: permanent and pH-dependent charge components of cation exchange capacity
Authors: Kapoor B. S.
Published: December 2006

The cation exchange capacity (C.E.C.) of nontronite was determined by titrating the acid clay, prepared by the action of H-resin on nontronite, in water and some nonaqueous solvents. The base-titratable acidities of the acid nontronite, freshly prepared as well as aged, were found to be greater than the acidities extractable with 1 N NaCl; the difference was attributed to the non-exchangeable pH-dependent component of C.E.C. In the freshly prepared sample, H+ and Fe3+ ions were the only exchangeable cations. Ageing produced basic Fe ions which were exchangeable and whose amount increased at the cost of H− and Fe3+ ions. Whatever the age, the total quantity of these exchangeable cations corresponding to the total isomorphous charge, remained constant. The amount of the pH-dependent acidity also remained unchanged. A likely mechanism to account for the observed pH-dependent component of the C.E.C, of nontronite is suggested.
The Vermiculitization of Trioctahedral Micas
Authors: Rousseaux J. M. , Rouxhet P. G. , Vielvoye L. A. , Herbillon A. J.
Published: December 2006

The alteration of thirty-nine trioctahedral micas to vermiculite has been characterized by the K level, which is determined by repeated measurements of the stationary K concentration in the altering solution and provides a practical way of comparing the sensitivity to alteration. A calculated regression equation allows the K level of a sample to be predicted from its chemical composition. The model proposed for the alteration reaction outlines the physico-chemical meaning of the K level, with its experimental and theoretical limitations.
Palygorskite from Warren Quarry, Enderby, Leicestershire, England
Authors: Tien Pei-Lin
Published: December 2006

Specimens of palygorskite from Warren Quarry, Enderby, Leicestershire, have been studied in the laboratories. The mineral is found in dioritic rocks in association with angular dolomitic rock fragments as the filling material of a joint, the walls of which are sometimes lined with calcite and dolomite. Palygorskite occurs as 3-10 mm long bundles of fibres, 0·03-0·1μm wide. X-ray diffraction data indicate that the mineral may occur in the monoclinic form. The structural formula for the half-unit cell is Si8(Al1.89Fe0.053+Ti0.01Mg1.99)O20(OH)2(OH2)43·61 H2O.Ca0.07. Data obtained from differential thermal and infrared analyses are comparable with those for palygorskite in the literature, but the six-sided transversal cross-section of the fibres as revealed by electron microscopy is unexpected. The mineral was formed after the deposition of the overlying basal Triassic rocks when ground waters penetrated cracks in the dioritic rocks, causing Si and Mg to be released there and above the unconformity.
The Formation of Hydroxy Interlayers in Smectites under the Influence of Organic Bases
Authors: Heller-Kallai L. , Yariv S. , Riemer M.
Published: December 2006

Sorption of molecular amines by montmorillonite involves protonation of the amine group and hydrolysis of the interlayer cation. Sorption and subsequent desorption of amines may render some of the interlayer cations non-exchangeable, thus causing partial 'chloritization' of the montmorillonite. The effect is stronger with interlayer Al than Ca ions and depends upon the amine sorbed.
Activation of Non-Swelling Bentonite
Authors: Bleifuss R. L.
Published: December 2006

Examination of field samples shows that the alteration of the bentonite beds of Wyoming and Montana near the surface to produce high-quality, highswelling, commercial bentonites is analogous to pedocal soil development. The near surface bentonite has undergone extensive calcification, and in some zones it is so heavily altered as to diminish its swelling properties. These low-swelling bentonites can be activated by conventional soda-ash additions. The naturally high-swelling materials have undergone only partial calcification and do not require soda-ash modification. The relatively unaltered 'grey' or 'blue' bentonites have undergone little or no calcification. The latter have the highest Na to Ca ratios, are non-swelling, and do not respond markedly to soda-ash additions. Such low-swelling materials will respond to calcium-activation with markedly improved physical quality parameters of flocculation as measured by Marsh Funnel and Fann viscosimeter. The study indicates that vast reserves of low-swelling bentonites in Montana-Wyoming may be susceptible to controlled calcium activation and expanded commercial utilization.
The Adsorption of Aromatic, Heterocyclic and Cyclic Ammonium Cations by Montmorillonite
Authors: Vansant E. F. , Uytterhoeven J. B.
Published: December 2006

The adsorption of organic ions derived from ammonium, containing aromatic and saturated rings, was studied using different techniques. The ions with acid character produced a complicated set of reactions including aluminium extraction, proton adsorption, a real ion-exchange with the organic ions and an excess adsorption of ammonium salts. With non-acidic compounds only a stoichiometric ion-exchange process was observed. X-ray diffraction and infrared spectroscopy were used to determine the orientation of the organic ions and to characterize the nature of the co-adsorbed organic material.
The Formation of 2:1–2:2 Intergrade Clays in some Norwegian Podzols
Authors: Kapoor B. S.
Published: December 2006

The distribution of 2:1-2:2 intergrade clays has been investigated in some podzolized soils from Norway. In some of the profiles the intergrade clay mineral appears to be concentrated in the A2 horizon; in others, where smectite is predominant in the surface horizon, the maximum accumulation of the intergrade is observed in the B2 horizon. Smectite and vermiculite have been found to be the precursors of the intergrades of the A2 and B2 horizons respectively. A possible explanation to account for the observed variable pattern of occurrence of intergrades in soils is suggested.
The Clay Mineralogy of the Haldon Gravels
Authors: Hamblin R. J. O.
Published: December 2006

The less than 10 μm and less than 3 μm fractions of the heterogenous Haldon Gravels have been examined by X-ray diffractometry. Kaolinite of high to low crystallinity is the dominant clay mineral, with variable amounts of illite (clay mica) ; quartz, a little feldspar and anatase also occur. The kaolinite has been ranked using the crystallinity index of Hinckley and also by indices derived from the ratio of peak height to background height for the 10 and 11 peaks.

Clay from the matrix of the psaphitic members of the Buller's Hill Gravel contains intermediate grade kaolinite with a little illite, but clay bodies included in this formation contain only low grade kaolinite with a high, but variable proportion of illite. The Tower Wood Gravel contains two distinct populations; one is identical to that of the Buller's Hill Gravel, the other consists of high crystallinity kaolinite with a little illite. Head Gravel formed from the Buller's Hill Gravel by solifluction contains intermediate to low crystallinity kaolinite.
Thickening Flocculated Kaolinite Slurries in the Nozzle Discharge, Multidisc, Bowl Centrifuge
Authors: Brociner R. E. , Vollans E. C.
Published: December 2006

Three semi-empirical equations are derived to characterize the performance of the nozzle discharge centrifuge as a thickener for flocculated kaolinite slurries. The first equation relates mass throughput to machine size and speed, the number and size of nozzles and the product concentration. The second equation relates the maximum clear effluent rate to the settling characteristics of the slurry and to machine parameters. The third equation relates power consumption to product and effluent rates and to machine parameters. Finally a numerical example of the use of the equations is given.
The Alteration Characteristics of the Lower Oxford Clay
Authors: Jackson J. O.
Published: December 2006

Alternating 'hard' and 'soft' bands at close intervals are exhibited by the slope faces of brick-pits in the Lower Oxford Clay which have been subjected to prolonged exposure. This phenomenon was investigated to evaluate the geotechnical properties which were significant in its development. The results of laboratory tests indicate that the alteration or short-term weathering characteristics of clay-shales may be influenced by the higher degree of preferred orientation of the clay-mineral component, in inducing a stronger inter-particle bond in 'hard' samples which inhibits weathering.
A lithium-bearing aluminian regular mixed layer montmorillonite-chlorite from Huy, Belgium
Authors: Brown G. , Bourguignon P. , Thorez J.
Published: December 2006

A bluish-green clay found in veins cutting across brecciated slates of the Llanvirnian stage at Huy, Belgium, is shown by X-ray diffraction and chemical analysis to be a lithium-bearing, aluminium-rich, regular mixed layer montmorillonite-chlorite with associated pyrophyllite, nacrite and quartz and smaller amounts of calcite and ankerite. The cation exchange capacity of the purified air-dry magnesium saturated clay is 49 mEq/100 g and its structural formula is

The problem of the nomenclature of regular mixed layer montmorillonite-chlorites is discussed.
Illites en lattes, illites pseudohexagonales, processus de formation: experimentation
Authors: Mosser Ch.
Published: December 2006

Le Grès à Voltzia des Vosges du Nord est formé de bancs gréseux et de lentilles argileuses. Les illites extraites des bancs gréseux montrent au microscope électronique des formes en lattes alors que celles des lentilles argileuses ont des contours pseudohexagonaux. Lorsqu'on broie une muscovite dans de l'eau désionisée avec du sable de Fontainebleau on retrouve ces deux formes, en lattes et pseudohexagonales. Les deux formes de particules peuvent donc être engendrées par un mème materiel initial.

Une hypothèse a été faite quant à la formation des illites en lattes. Elles seraient le résultat d'une dissection de particules micacées le long des rangées de substitution [10], [11] et [1] du silicium tétraédrique par de l'aluminium avec perte d'une partie de cet aluminium. Des analyses chimiques et des observations au microscope électronique ont été faites sur des particules de muscovite broyée. Les résultats obtenus vont dans le sens de l'hypothèse émise mais ne sont pas suffisants pour la démontrer pleinement.
Mineralogical changes associated with deep weathering of gabbro in Aberdeenshire
Authors: Basham I. R.
Published: December 2006

The distribution, profile morphology and mineralogy of deeply weathered gabbroic rocks in the basic igneous masses of Insch and Bogancloch, Aberdeenshire, have been studied. The saprolite is characterized by granular disintegration and spheroidal weathering with a relatively low degree of secondary mineral development. The upper part of the profile often shows evidence of mass movement and incorporation into overlying drift but below this zone the degree of alteration is generally uniform with depth. Feldspar and hornblende are largely unaffected, except by disintegration, but pyroxenes show varying degrees of weathering from the incipient development of amorphous iron oxides to replacement by reticulate networks or complete pseudomorphs of trioctahedral vermiculite. Biotite weathers to hydrobiotite and vermiculite, giving rise also, under certain conditions, to kaolinite-gibbsite vermiforms. The correspondence between occurrences of deep weathering and coarser textured biotite-bearing rocks can be related to the instability of this mineral. Consideration of the mineralogical changes found and the morphology of the profile of weathering suggest their formation under a warm, humid climatic regime, probably during the mid Tertiary times.
Surface acidity of imogolite and allophane
Authors: Henmi T. , Wada K.
Published: December 2006

The acid strength and the number of acid sites on various clays were determined by observing the colouration of Hammett indicators adsorbed on them and by titrating benzene suspensions of them with n-butylamine, respectively. H(Al)-saturated allophane behaves as a strong acid (Ho; −5·6 ∼ 1·5) in a relatively dry environment (relative humidity 10-55%), but its acid strength is very much reduced either by increasing its water content or by saturating it with alkali or alkali earth metal cations. Imogolite shows only a very weak acidity (Ho; 4·6 ∼ 6·8) under medium dry to moist conditions (relative humidity; 30-100%). Both allophane and imogolite show a marked enhancement of acidity (Ho; −8·2 ∼ 1·5) when they have been dried over P2O5 or heated to result in dehydroxylation. H(Al)-saturated montmorillonite, kaolinite and halloysite show stronger acidities (Ho; −5·6 ∼ 1·5) than allophane (Ho; 1·5 ∼ 6·8) in a relatively moist environment (relative humidity; >60%). The n-butylamine titre and CEC show a good agreement for montmorillonite, but a poor agreement for allophane. The latter discrepancy which is larger for allophane when it has been heated at 150 and 300°C, is also found for imogolite when similarly heated. In these titrations, excess butylamine is found in supernatants at end-points. Therefore, the n-butylamine titre as such can not be used for the estimation of the number of acid sites on imogolite and allophane. The origin, structure and transformation of the acid sites on these clays is discussed.
Electron spin resonance studies of doped synthetic kaolinite. I
Authors: Angel B. R. , Jones J. P. E. , Hall Peter L.
Published: December 2006

Synthetic kaolinites of varying crystallinity, and in some instances with ideal morphology, have been produced by hydrothermal reaction of aluminiosilicate gels. Synthetic kaolinites doped with Mg2+ and Fe3+ were also obtained.

Synthetic kaolinite doped with Fe3+ produced an ESR spectrum at g = 4 identical to spectra observed in natural kaolinites. Following X-irradiation and annealing at ~200°C, synthetic kaolinite doped with Mg2+ exhibited an ESR signal at g = 2·0 identical to a resonance observed in natural kaolinites. It is concluded that the g = 2·0 signal in kaolinite is due to a defect centre stabilized by Mg2+ substitution.

All synthetic and natural kaolinites exhibit an additional resonance at g = 2·0 following X-irradiation which can be repeatedly created and destroyed by irradiation and annealing. This resonance is attributed to defects possibly associated either with the substitution of Al3+ for Si4+ in kaolinite or with lattice vacancies.
Electron spin resonance studies of doped synthetic kaolinite. II
Authors: Jones J. P. E. , Angel B. R. , Hall Peter L.
Published: December 2006

It is shown from studies of synthetic kaolinites doped with Fe3+ that the ESR spectrum of kaolinite at g = 4 consists of two components attributed to Fe3+ ions occupying two distinct substitutional sites (Centres I and II). The relative intensity of the two components can be correlated with the X-ray crystallinity of the samples. The ESR spectrum is influenced by artificial changes in crystallinity produced by subjecting samples to high stresses or by intercalation. It is concluded that Centre II is due to Fe3+ replacing Al3+ in the octahedral layer in a region of high crystallinity. Centre I is assigned to Fe3+ occupying Al3+ sites distorted by changes in the hydroxyl orientations associated with layer stacking disorder or disruption of interlayer bonding.

A stable defect centre in kaolinite which produces an ESR spectrum at g = 2·0 is attributed to either a hole centre located on an Si—O bond adjacent to an Mg2+ octahedral impurity or to an O2− ion trapped within the lattice.
The nature and nomenclature of hydrous nickel-containing silicates
Authors: Brindley G. W. , Maksimovic Z.
Published: December 2006

Nickel ions play similar roles to magnesium ions in nickel-containing hydrous layer silicates. The extent of the replacement of Mg by Ni ranges from small proportions to complete, or almost complete, replacement. Particular interest attaches to the micro-crystalline, clay grade, minerals formed by processes of lateritic weathering. The multiplicity of names proposed in pre-X-ray-diffraction times must be re-evaluated in terms of modern identification procedures. Many of these minerals can now be placed in series such as:

Garnierite is now used mainly as a field term, prior to more specific identification, and terms such as 7 Å- and 10 Å-garnierite are useful when identification can proceed no further than recognition of basal spacings. Further study is required of schuchardtite, and of nickel-containing smectites and sepiolites. Consideration also must be given to the composition ranges of the end-member names.
Maghemite in soils and its origin
Authors: Taylor R. M. , Schwertmann U.
Published: December 2006

The products of air oxidation of mixed Fe(II)-Fe(III) chloride solutions at pH 6 and 7, at 20 and 60°C and at normal pressure contain green rust, maghemite, lepidocrocite, goethite and a paracrystalline ferric hydroxide (ferrihydrite). Among these maghemite, a cubic ferromagnetic iron oxide (Fe2O3) found in many soils, is favoured by slow oxidation rate, high total Fe concentration, the presence of small amounts of Fe(III) in the original predominantly Fe(II) solution, higher temperature and at pH 7 rather than pH 6. The green rust is believed to be an essential precursor of maghemite. On slow oxidation it will form maghemite probably via magnetite. Fast oxidation prevents the cubic phase from being formed and lepidocrocite is the end product. At higher Fe(III) proportions ferrihydrite can be formed which under certain influences converts to goethite and/or hematite. The common iron oxides are seen to form from the same system from small variations in environment which is to be expected from their common associations in soils
Clay mineralogy of sediments of the western Nile Delta
Authors: Weir A. H. , Ormerod E. C. , El Mansey I. M. I.
Published: December 2006

Investigation of the clay mineralogy of forty-seven samples of sediments from boreholes in the western Nile Delta, an area little studied hitherto, and from surface sites on the mouth of the Nile and adjacent coast shows that the clay fractions consist of dominant iron-rich, dioctahedral, randomly interstratified smectite-illitcs together with kaolinite, illite and chlorite.

Amounts of the constituent minerals of the clay fractions are estimated from their X-ray diffraction intensities, supported by selective dissolution chemical data, and a new method is used to estimate the proportion of expanding layers in randomly interstratified smectite-illite. The results, which confirm and extend the work of previous investigators, also show that there is little correlation between the clay mineral composition and texture of the sediments, only kaolinite being weakly linearly correlated with clay content. Transformation of 2:1 layer silicate minerals occurs within the buried sediments ; chlorite is transformed and smectite and illite interlayers redistributed within randomly interstratified smectite-illites.
Chlorite and illite in some lower Palaeozoic mudstones of mid-Wales
Authors: Evans L. J. , Adams W. A.
Published: December 2006

Lower Palaeozoic mudstones from Cwmcadian, Gwynedd are dominantly composed of quartz, illite and chlorite, with subordinate albite, orthoclase and rutile. Chemical formulae are determined for chlorite and illite using a combination of chemical and X-ray data. The formulae indicate that the illite is dioctahedral and suggest that the chlorite structure contains one dioctahedral and one trioctahedral layer. The hypothesis is put forward that both minerals formed from a dioctahedral mineral; illite from a non-expanded form and chlorite from an 'open' form by precipitation of a Fe2+/Mg hydroxide interlayer.
Lath-shaped montmorillonites in Surrey
Authors: Neumann Barbara S.
Published: December 2006

Electron microscopic examination of montmorillonite from the deposit near Redhill shows that the particles of the so-called blue clay are predominantly lathshaped with an average length: width ratio of 5. The so-called yellow clay from Redhill also contains a high proportion of similar lath-shaped particles, but many smaller lamellar particles are present which appear to be the results of lateral fracture of the laths. The majority of particles of montmorillonite in the fullers' earth deposit near Bath, Somerset, are platy with a similar shape distribution to Wyoming Bentonite, although smaller in size.

The electron microscopic technique used is based on a positively charged supporting film which, immersed in a clay suspension, preferentially selects negatively charged montmorillonite from the predominantly uncharged impurities. A conventional replica technique also showed lath-shaped particles in the blue clay.

The possible practical consequences of the different particle shapes are discussed.
Influence de la stereochimie des diols sur la formation des complexes interfoliaires de la montmorillonite calcique
Authors: Chassin P.
Published: December 2006

Dans ce travail, nous avons determine les caractéristiques des états d'équilibre de la montmorillonite calcique placée dans la phase vapeur délivrée par des solutions aqueuses d'éthane 1·2 diol, de propane 1·2 diol, de propane 1·3 diol, de butane 1·3 diol, de butane 1·4 diol et de butane 2-3 diol.

Les diagrammes de sélectivité, calculés à partir des isothermes d'adsorption, la diffraction des rayons X et la spectroscopic infrarouge mettent en evidence l'existence de deux phases adsorbées ayant des caractéristiques très différentes.

(1)

Une phase interagrégat dont la composition est égale à celle de la solution d'équilibre.

(2)

Une phase interfoliaire dont les caractéristiques sont étroitement liées à la stéréochimie de la molécule organique.

Les différents états stables mis en evidence s'expliquent par les energies mises en jeu par les interactions cations dipoles et les liaisons hydrogène intermoléculaires.
Signification de la mesure des surfaces totales des argiles avec l'ethane 1·2 diol
Authors: Chassin P.
Published: December 2006

L'exploitation des diagrammes de sélectivité de la montmorillonite, en equilibra avec la phase vapeur délivrée par des solutions aqueuses d'éthane 1-2 diol, permet de montrer que la quantité de diol interfoliaire est supérieure a 25 % et qu'elle est directement reliée à la chaleur d'hydratation des cations compensateurs.

Les cinétiques de désorption, réalisées à plusieurs températures, permettent de retrouver les mèmes résultats, à savoir que l'encombrement moléculaire depend du cation compensateur.

Ainsi, la mesure des surfaces totales des minéraux argileux avec l'éthane 1·2 diol n'a de sens que si, d'une part, on opere toujours avec le mème cation (σm = cte) et, d'autre part, on determine la quantité de diol en contact avec la surface à partir de plusieurs cinétiques de désorption réalisées à différentes temperatures.
Observations on the formation of kaolinite in the St. Austell granite, Cornwall
Authors: Exley C. S.
Published: December 2006

Partial chemical and X-ray analyses of specimens taken serially from three different rock types from the St. Austell granite show that potash feldspar is hydrothermally altered to a micaceous mineral. Sodic plagioclase alters to mica, montmorillonite and kaolinite. Furthermore, in the latter case the micaceous mineral and montmorillonite are intermediate products between feldspar and kaolinite. It is believed that the level of H+ion activity in the altering solutions controlled the removal of alkalis, Al2O3and SiO2so as to leave appropriate concentrations of these constituents to re-form as mica or montmorillonite. Further alteration of a similar kind produced kaolinite.
Polymerisation en phase aqueuse d'acides amines sur des argiles
Authors: Brack André
Published: December 2006

L'action catalytique des argiles sur la polymérisation des acides aminés en solution aqueuse a été étudiée. Les résultats rapportés par Katchalsky et coll. dans le cas de la polymérisation de l'analyl adenylate en presence de montmorillonite n'ont pu ètre reproduits. D'autres types d'activation des acides aminés ont été examines.
Smectite, chlorite and a regular interlayered chlorite-vermiculite in soils developed on a small serpentinite body Massif Central, France
Authors: Ducloux J. , Meunier A. , Velde B.
Published: December 2006

Three soil profiles developed on a serpentinite body (La Rochel'Abeille, near Limoges) show three stages of weathering. All soils contain iron-rich smectites and secondary chlorites. The latter are very silica-rich, more so than 14 Å chlorites from crystalline rocks. In the (B)1g horizon of the hydromorphic profile, these minerals seem to give a reaction of the type:

This reaction, typical of a closed system, appears to be operative in a soil profile which is certainly, in part, open to chemical migration. The chemistry of the weathered serpentinite and the chemical composition of newly formed minerals as well as those of the serpentinite are used to indicate the chemiographic relations of clay minerals formed in the weathering profiles.