bluuebunny/crossref_metadata_2025 huggingface dataset:
The formation and mineralogy of bentonites in Azerbaijan
Authors: Seidov A. G. , Alizade Kh. A.
Published: December 2006

Cretaceous and Eocene bentonites from Azerbaijan have been studied from the standpoint of their occurrence, mode of formation, and mineralogy. The bentonites are shown to be derived from the vitroclastic products of volcanic eruption by transformation in a marine environment.
Some factors affecting the relation between the clay minerals in soils and their plasticity
Authors: Dumbleton M. J. , West G.
Published: December 2006

The clay mineral composition is one of the factors that affect the physical properties of soils, and a knowledge of it is required to promote a fuller understanding of the origin of these properties. The relationships between the clay content and the plastic and liquid limits of natural montmorillonitic and kaolinitic soils and of artificial mixtures have been examined and compared. Factors affecting the relationships are discussed, and illustrated by the effect of particle aggregation on the measurement of the liquid limit of tropical red clays and on the sedimentation analysis of the Keuper Marl. The effect of muscovite and of silt-sized material on the position of soils on the Casagrande classification chart has also been examined.
Chlorite clay minerals in Ordovician pumice-tuff and derived soils in Snowdonia, North Wales
Authors: Ball D. F.
Published: December 2006

Calcareous volcanic ashes (pumice–tuffs) occur among Ordovician rocks in Snowdonia, North Wales. The clays of these rocks and of the ecologically important soils derived from them are found to be almost mono-mineralic and to consist of chlorites. Chemical, differential thermal and X-ray analyses are given and discussed with particular reference to a clay-size chlorite from weathered pumice–tuff. There is no evidence for pedogenetic clay mineral transformations in the range of soils studied.
Experimental studies of fine-grained micas
Authors: Rouxhet P. G. , Brindley G. W.
Published: December 2006

The water gained by two micas during a wet-grinding process (extra-water) has been evaluated. It was found to be proportional to the surface area and the amount was about 29 µmoles/m2 for a fluorphlogopite and about 16 µmoles/m2 for a muscovite. This estimation was made possible by eliminating the physically adsorbed water. The material contaminating the surfaces and the constitution water of muscovite were taken into account by the comparison of the two minerals and by the use of infrared spectroscopy in addition to thermovolumetric data. It is thought that the extra-water is related to a disordered and chemically modified surface layer of the particles. The bearing of these results on the nature of illite is indicated.
Ethylene glycol and glycerol complexes of smectites and vermiculites
Authors: Brindley G. W.
Published: December 2006

The complexes formed by ethylene glycol, HOCH2.CH2OH, and by glycerol, HOCH2.CHOH.CH2OH, with smectites (montmorillonite-saponite group), and vermiculites have received more attention than any other group of organo-silicate complexes. This interest arose in the first place from their use for identification purposes as proposed by MacEwan (1944, 1946) and by Bradley (1945b). Over the years, increasing attention has been given to the manner in which these complexes vary with the nature of the mineral, the magnitude and source of the charge on the silicate layers, and the number and kind of the exchangeable cations between the layers. The layer charge is determined most reliably from the full chemical analysis of a mineral, but more commonly is estimated from a measurement of cation exchange capacity.
A study of a long-spacing mica-like mineral
Authors: Cole W. F.
Published: December 2006

An interstratified clay mineral from Surges Bay, Tasmania, described by Cole & Carthew (1953) as containing a random stacking of illite and montmorillonite in the ratio of 3:2 and a regular stacking of illite and montmorillonite in the ratio of 1 : 1 is re-examined, after purification, and a new interpretation is made of the X-ray diffraction effects in terms of a single complex stacking model. The Fourier transform method of analysis used with an appropriate layer structure factor shows that the interstratification is produced by a three component stacking of 18% single mica layers (A), 10% double mica layers (ĀĀ) and 72% allevardite-like layers (ĀB̄) in which the A and ĀĀ layers are never together. This leads to the conclusion that the near regular interstratification of the mineral is due to structural and/or compositional variation from layer to layer within the parent crystals as suggested by Sudo, Hayashi & Shimoda (1962) to explain similar mineral types occurring in Japan.
Chemical changes during the alteration of micas
Authors: Newman A. C. D. , Brown G.
Published: December 2006

Di- and trioctahedral micas were altered to vermiculite-like minerals by extracting the K with sodium tetraphenylboron. Chemical analysis of original and altered micas shows that loss of K is accompanied by an increased loss on ignition, oxidation of some Fe2+ to Fe3+, loss of divalent octahedral cations, mainly Mg2+, loss of OH− (or sorption of H+) and decrease in net negative charge.

The following reactions are suggested to explain these changes: (1) replacement of K by Na at interlayer sites; (2) release of structural OH− ions exposed by replacement of K, which decreases the negative charge and allows the structure to expand and more K to be replaced; (3) oxidation of Fe2+ ions by the reaction

4Fe2+ + 4 structural (OH−) + O2 → 4Fe3+ + 4 structural (O2−) + 2H2O;

and (4) release of divalent octahedral ions, possibly through some of the holes left when structural OH− is lost.

The wide implications of these proposals are discussed.
Thixotropy and dilatancy
Authors: Cashen G. H.
Published: December 2006

The matric potential of water in gels of five-sixths neutralized aluminium montmorillonite (bentonite) and aluminium kaolinite changes during periods of shear and periods of rest. Shear increases the potential of water in bentonite gels, and in kaolinite gels containing little water, but decreases the potential in kaolinite gels containing more water. All these effects can be explained by changes in the curvature of water films at the gel-air interface. The difference between thixotropic and dilatant behaviour is the increasing and decreasing of the water potential on shearing. In dilatant pastes of silt-size particles, and for which the effects of electric charges are small, the pressure deficiency can reach large values after an increase in pore space, and this suffices to explain the characteristic features of dilatant behaviour.
Stages in the tropical weathering of kimberlite
Authors: Fairbairn P. E. , Robertson R. H. S.
Published: December 2006

Numerous exposures of highly altered kimberlites in exploratory trenches and pits have afforded an opportunity of studying the very great changes which take place chemically and mineralogically under conditions of tropical weathering in Sierra Leone.
Clay minerals and geomorphology in four Caribbean islands
Authors: Beaven P. J. , Dumbleton M. J.
Published: December 2006

Clay mineral analyses of Caribbean soils illustrate the differences in composition that can arise from differences in topography and parent material, and emphasize the differences between the groups of proposed new engineering classifications of the soils based on these factors. Within one set of environmental conditions the clay mineral assemblage was reasonably constant. Examples are given of local differences in clay type which were correlated with variations in climate and mode of formation.
Adsorption of alkylammonium cations by montmorillonite
Authors: Theng B. K. G. , Greenland D. J. , Quirk J. P.
Published: December 2006

The adsorption of various alkylammonium cations from aqueous solution by sodium and calcium montmorillonite has been studied. Adsorption occurred through an exchange reaction between the inorganic cations on the clay and the alkylammonium ions in solution. The affinity of the clay for these cations was linearly related to molecular weight, with the exception of the smaller methyl-ammonium and the larger quaternary ammonium ions. Comparison of primary, secondary and tertiary amines containing the same alkyl groups showed that the affinity of the clay was greatest for the primary amine and least for the tertiary. This behaviour has been interpreted in terms of the size and shape of the cations. X-ray diffraction analysis showed that no more than a single layer of adsorbed cations was present in the inter-lamellar space at maximum adsorption. Comparison between Δ-values and the thickness of the adsorbed ions showed that there was a contraction in the apparent contact distance of these cations. The amount of contraction could be accounted for by ‘keying’ of the adsorbed ions into the montmorillonite surface.
Partially-ordered mixed-layer mica-montmorillonite from Maitland, New South Wales
Authors: Hamilton J. D.
Published: December 2006

A mixed-layer clay mineral from a Permian sandstone at Maitland, New South Wales has been identified as 2:1 mica-montmorillonite structure with ‘imperfectly regular’ interstratification. The results from Fourier transform analysis and Fourier synthesis of 00lX-ray diffraction data have not fully elucidated the interlayering patterns but have indicated that there is complete alteration in the stacking and that the 1:1 (allevardite type) layer sequence relationship is strongly developed.

X-ray diffraction, differential thermal, thermogravimetric, chemical, cation exchange and electron microscopic data for the mineral are given. The chemical analysis for the Na+-saturated material gives the structural formula

K0.90Ca0.06Na0.49[Al3.52, Fe0.183+Mg0.27Ti0.03(Al1.24Si6.76) O20(OH)4] H2O

It is considered that most of the fixed K+and Ca++ions are probably held in the mica interlayers, while the exchangeable components are largely accommodated in the expanded montmorillonite zones.
The clay mineralogy of some soils derived from a biotite-rich quartz-gabbro in the Strathdon area, Aberdeenshire
Authors: Wilson M. J.
Published: December 2006

Three soils of the Strathdon area, Aberdeenshire, derived from a biotite-rich quartz-gabbro and representing well-drained, imperfectly drained and poorly drained types, were studied. The 50–200 µ fractions contained mainly plagioclase feldspar, amphibole (tremolite and hornblende), biotite and quartz and the following order of relative stability was established: quartz > amphibole > plagioclase feldspar > biotite. In all soils biotite was found to weather to a 14 Å aluminous vermiculite-chlorite with zones of kaolinite. The clay mineral composition of three soils was identical, consisting of trioctahedral vermiculite-chlorite, trioctahedral illite, kaolinite and gibbsite. These minerals originated in various ways through the decomposition of biotite which thus plays a key role in the origin of the clay fraction. It is suggested that the clay mineral constituents of the soils were formed in a regolith predating the last glacial period, and that post glacial soil-forming processes have modified them only slightly.
Interactions of n-alkylammonium ions with mica-type layer lattices
Authors: Walker G. F.
Published: December 2006

The literature on the complexes of n-alkylammonium ions with layer silicates is characterized by marked divergences, not only in the deductions and conclusions of the different investigators but also in their experimental results. An attempt is made to reconcile and rationalize the differences, and to form a self-consistent picture of these systems.

Given a saturating solution of sufficient concentration, the complexes tend during their formation to adopt an arrangement in which silicate layers are separated by double layers of ions oriented so that the alkyl chains are extended away from the silicate surfaces at a high angle. Water molecules, salt and free alkylamine may also be present in the interlayer spaces. When the excess material is removed by washing and the complexes dried, ideally the alkyl chains from opposing surfaces move over one another and interpenetrate so as to form a single layer of ions. During the contraction, however, the chains interact with one another and tend to stick at some point short of complete interpenetration. Weak attractive forces acting to bring the silicate layers together, and consisting mainly of electrostatic forces originating in the mineral layers and van der Waals interactions arising from increasing association of opposing alkyl chains with increasing interpenetration, are insufficient to overcome this tendency fully. As a result, an alkyl chain of given length can give rise to a series of complexes differing in their XRD characteristics.

Previous workers have noted the difficulty of achieving reproducible results and some have recommended grinding the complexes, but it appears that this treatment significantly alters the nature of the end-product.
Changes in phlogopites during their artificial alteration
Authors: Newman A. C. D.
Published: December 2006

When phlogopites containing only a little iron are artificially altered with sodium tetraphenylboron solutions, the vermiculite-like products contain fewer interlayer cations than the original micas. Structural formulae of the products are calculated from the chemical analyses, together with infrared examination of the angular vibration band of water at 1650 cm−1 to distinguish between water of hydration and hydroxyl groups. The formulae obtained are consistent with the weight-loss curves and show that the products contain, more than 4(OH,F) per formula unit. The interpretation of these formulae is that the silicate layers lose net negative charge by protonation of structural oxygen anions to form new hydroxyl groups.
Stability of hectorite in weakly acidic solutions. I. A chemical study of the dissolution of hectorite with special reference to the release of silica
Authors: Tiller Kevin G.
Published: December 2006

The dissolution of hectorite suspensions in M/20 CaCl2 has been studied under conditions of low acidity. The reaction was almost completed within 2 weeks but very slow changes continued. There was an initial preferential release of Mg which corresponded approximately to the number of Mg atoms exposed at the clay edges but thereafter Mg and Si were released into solution in nearly equimolar amounts until most of the clay was decomposed. The release of octahedral cations was equivalent to the amounts of H+ ions added. Some earlier views on the acid attack of 2:1 clays were supported. With increasing amounts of acid added, the Si released into solution as monosilicic acid become supersaturated before final precipitation as amorphous silica of high surface area.

The molar proportion of Si/Mg released into solution was less than that of the original sample yet there was no chemical or X-ray evidence of the development of significant siliceous ‘fringes’. The residues of the tetrahedral layer probably separate continually, thus maintaining the same kind of reaction surface throughout the reaction, without passing into solution or forming a stable sol. Acid attack in the presence of excess silicic acid did not result in any appreciable selective dissolution of octahedral layer.
The effect of exchangeable alkylammonium ions on the swelling of montmorillonite in water
Authors: Theng B. K. G. , Greenland D. J. , Quirk J. P.
Published: December 2006

A study has been made of the influence of adsorbed alkylammonium ions on the water sorption and swelling of Na+ and Ca++ montmorillonite, under controlled conditions of temperature and suction. The water uptake and extensive crystalline swelling of Na+ montmorillonite decrease as the proportion of exchangeable alkylammonium/ammonium ions increases. This decrease is more associated with the degree of surface coverage than with the degree of saturation of the exchange sites by the alkylammonium ions. These observations are explained in terms of binding of the organic cation by the clay surface and the collapse of diffuse double layers on interlamellar surfaces. Differences in water uptake betwen complexes saturated with different alkylammonium ions are attributed to differences in the structural arrangement of the clay crystals in the swollen state. Similarly, there is a continual slight decrease in the water uptake and swelling of Ca++ montmorillonite as the amount of alkylammonium ions present increases. However, for alkylammonium ions containing less than five carbon atoms and when only about half of the exchangeable Ca++ ions have been replaced by the organic ions, extensive crystalline swelling sometimes takes place. When this occurs, it is suggested that the alkylammonium ions disrupt the regularity of the water network initially associated with the Ca++ ions, enabling these to participate in the formation of diffuse double layers in the interlamellar space.
Reactions catalysed by minerals. IV. The mechanism of the benzidine blue reaction on silicate minerals
Authors: Solomon D. H. , Loft B. C. , Swift Jean D.
Published: December 2006

The oxidation of benzidine to benzidine-blue on silicate minerals is shown to occur at aluminium atoms exposed at crystal edges and at transition metal atoms in the higher valency state present in the silicate lattices. The transition metals in the silicate lattice undergo chemical oxidation-reduction reactions.

Changes in the colour of the benzidine-blue radical cation with the conditions of reaction are discussed in terms of the solvent used for the reaction and its influence on the pH of the mineral surface.
Reactions catalysed by minerals. V. The reaction of leuco dyes and unsaturated organic compounds with clay minerals
Authors: Solomon D. H. , Loft B. C. , Swift Jean D.
Published: December 2006

The mechanism of colour reactions of clay minerals with amines, diphenylpicrylhydrazyl, tetracyanoethylene, and leuco bases are elucidated, and the results used as a guide to the reaction mechanism of polymerization reactions catalysed by clay surfaces.
A study of some glauconites from cretaceous and tertiary formations in South-East England
Authors: McRae S. G. , Lambert J. L. M.
Published: December 2006

A study of soil formation on glauconitic parent materials in South-East England has included a mineralogical investigation of glauconite grains, heretofore identified solely by morphology. The grains have been subjected to X-ray diffraction, differential thermal and partial chemical analyses, and have been found to consist essentially of randomly interstratified micaceous and montmorillonitic clay mineral; thus all are glauconite sensu lato. Only small amounts of non-clay mineral impurities have been detected. The proportion of expandable layer material has been found to be related to the % K2O and cation exchange capacity of the specimens.
The clay mineralogy of the molasse formations of Azerbaijan and its correlation with paleogeography
Authors: Seidov A. G. , Pashaly N. V.
Published: December 2006

An investigation of the clay mineralogy of the molasse formations of Azerbaijan has been carried out. The results have been correlated with climate, the geochemistry of the basin of deposition, the parent rocks and the tectonic stability both in the area of erosion and the zone of accumulation. A knowledge of the relationship between these factors and the clay mineralogy of the sediments may help in the solution of paleogeographic problems.
A scheme of semi-micro analysis for the major elements in clay minerals, based on modifications to conventional methods of silicate analysis
Authors: Pruden G. , King H. G. C.
Published: December 2006

A scheme is presented for the semi-micro analysis for the major elements in clay minerals, based mainly on improvements to conventional colorimetric methods. Silica and alumina are determined after fusing a 50-mg sample with sodium hydroxide. Titanium, total iron, calcium, magnesium, phosphorus and manganese are determined colorimetrically on a hydrofluoric-sulphuric acid digest of a 50-mg sample; sodium and potassium are determined flame photometrically on the same digest. Ferrous iron is determined separately. Additional methods for the determination of total water, total sulphur and fluorine are indicated.
A naturally occurring sodium vermiculite from Unst, Shetland
Authors: Curtis C. D. , Brown P. E. , Somogyi V. A.
Published: December 2006

A naturally occurring macroscopic sodium vermiculite from Unst, Shetland is described. It is similar in many respects to synthetic materials recently prepared from phlogopite by potassium replacement. In other respects, however, it is more akin to macroscopic Mg-vermiculites.
Hydrothermal reactions and crystallographic relationships found during the reactive hot pressing of kaolinites
Authors: Scott B. , Carruthers T. G.
Published: December 2006

Water released by dehydroxylation was trapped in clay compacts during reactive hot pressing. The dynamic conditions of water pressure and temperature produced in the compacts modified the high temperature reactions of kaolinite. Kaolinite was converted to pyrophyllite or mullite in the temperature range 600-700°C depending on the applied pressure. Oriented aggregates of clay were used to determine orientational relationships between kaolinite and the high temperature phases. Structural continuity was observed in the reactions through the basal planes of kaolinite and pyrophyllite to the (130) plane of mullite.
An X-ray investigation of some argillaceous rocks from the Skipton anticline, Yorkshire
Authors: Purton M. J. , Youell R. F.
Published: December 2006

X-ray analyses of argillaceous rocks from the Skipton anticline show that their average composition is quartz 30%, calcite 27%, feldspar 5%, illite 15%, kaolin 17%. Pyrite and other constituents account for the remaining 6 %. The quartz, calcite and feldspar are considered to be detrital, the variations in their quantity and size reflecting changes in the source of the sediments. The evidence indicates the general predominance of kaolin over illite, which is contrary to other published results on Carboniferous marine shales. A kaolin-rich source is necessary to account for the composition of the sediments. An occurrence of unusually pure and well-crystalline melanterite is recorded from the Draughton Limestone.
Effects of pretreatment on a 14 Å swelling mineral from Gartly, Aberdeenshire
Authors: Perez-Rodriguez J. L. , Wilson M. J.
Published: December 2006

A 14 Å swelling mineral, interlayered with what is probably an organometallic complex, occurs in the surface horizon of a gleyed soil near Gartly, Aberdeenshire. The interlayer material is thermally stable at 300°C and is easily removed by oxidation with H2O2 and NaOCl. Treatment with HCl and Na2EDTA destroys the ability of the mineral to expand with glycerol, although not if the clay is H2O2 treated beforehand. The Gartly clay mineral is also unusual in that Mg-saturation, using magnesium acetate at pH 7, leads to the rapid formation of brucite-like interlayers. It is concluded that in the investigation of soil clays it is best to avoid all pretreatments.
Imogolite: a unique aluminosilicate
Authors: Russell J. D. , McHardy W. J. , Fraser A. R.
Published: December 2006

The fibrous aluminosilicate imogolite has been studied by electronoptical and infrared absorption methods. Electron diffraction patterns are interpreted in terms of repeat units of 8·4 Å parallel and 23 Å perpendicular to the fibre axis. These spacings can not be reconciled with a continuous silicate chain structure and this conclusion is supported by an Si-O vibration near 930 cm−1. A structure is postulated in which distorted chains of Al-O octahedra are cross-linked through isolated Si2O7 groups.

Multiple OH stretching vibrations indicate different types of OH group in the imogolite structure. Absorption bands near 1000, 700 and 600 cm−1 are sensitive to sample orientation. This is attributed to the morphology and dimensions of the imogolite fibres.
A classification of kaolinites by infrared spectroscopy
Authors: Parker T. W.
Published: December 2006

A method is described for plotting and comparing measurements made on kaolinite clays. In this the ratio of the two strongest bands in the OH-stretch region of the spectrum (band maxima at 3695–3700 cm−1 and 3620–3625 cm−1) of an oriented preparation at 45° incidence is plotted against the corresponding ratio from the spectrum of a randomly oriented preparation. Both ratios are affected by the shape of the kaolinite particles and methods for minimizing this are given. The position of a kaolinite upon a plot so prepared gives information on the following points: (a) the type of kaolinite, (b) the degree of crystallinity of the kaolinite, (c) the shape of the kaolinite particles.
A Mossbauer study of the role of iron impurities in the high temperature reactions of kaolinite minerals
Authors: MacKenzie K. J. D.
Published: December 2006

Mossbauer spectroscopy was used to study the valence and bonding changes of iron in (a) lattice sites, and (b) cation exchange sites during thermal treatment of kaolinite and halloysite. Lattice iron which is initially in octahedral sites occurs in octahedral and tetrahedral sites at the completion of the thermal reactions. At temperatures below 650°C some divalent ions in cation exchange positions become trivalent and assume octahedral co-ordination, which they retain until the later stages of mullite formation. The implications of the work on the high temperature reaction mechanism and structural sequence are discussed.
Genesis of kaolin deposits of Birbhum, West Bengal, India
Authors: Mukherjee Bibhuti , Rao M. G. , Karunakaran C.
Published: December 2006

The mineral phases and the distribution of major, minor and trace elements in the clays and bed rocks of two bore-holes at Adda and Chaubatta of the Birbhum area have revealed an intimate relationship of the kaolin-rich clays with the bed-rock of Adda. The possibility of a common origin for the clay deposits at Chaubatta, lying close to the Rajmahal trap formations, and at Adda, lying close to the Archaean boundary, has been inferred from trace element distribution and other factors. A genetic relationship of the clay deposit at Adda with the bed-rock, altered Archaean gneiss, has been established, but there is no significant relationship of the Chaubatta clay deposit with its bed-rock, the weathered basalt.

The lateritic cappings above the kaolin-rich clays of Adda and Chaubatta areas are explained as being formed from kaolinite in the weathering sequence as the end-product of intensive desilication under conditions of intensive leaching and increasing acidity near the surface.
The role of thermal analysis in the evaluation of impure clay deposits as mineral raw materials
Authors: Bain J. A. , Morgan D. J.
Published: December 2006

Although Thermal Analysis is a useful technique in characterizing the clay constituent of a potentially valuable clay deposit, it is, perhaps, even more useful when the type and amount of non-clay impurities are important factors in its commercial appraisal. The effect of impurities on the physical and chemical properties of the clay may determine its potential uses in bulk, or it may be advisable to remove the impurity, either to improve the grade and quality of the clay or to provide a useful by-product. The application of both qualitative and quantitative thermal data, in the analysis and control of laboratory work in this field, is demonstrated by its use in the assessment of materials such as evaporite-rich clays, siliceous clays, and high-alumina clays.
Quantitative estimation of clay minerals by d.t.a.
Authors: Davis C. E. , Holdridge D. A.
Published: December 2006

Studies were conducted on the feasibility of using the Dupont 900 thermal analyser for quantitative estimation of clay minerals. The results indicate that kaolinite, gibbsite, goethite and calcite can be determined quite accurately and in small concentrations provided there are no serious interferences. Quartz in excess of 5 mg or more can be determined with a reasonable degree of accuracy. Approximate estimates of montmorillonitic contents of soil clays can be made by measuring the areas of the low temperature endotherms of samples which were equilibrated over saturated Mg(NO3)2.
Electron Optical Study of the Thermal Decomposition of Kaolinite
Authors: McConnell J. D. C. , Fleet S. G.
Published: December 2006

The electron microscope has been used to study the mechanisms of thermal decomposition of kaolinite in the temperature range 800-1350°C. Three main reaction mechanisms appear to be important in this temperature range. At 850°C metakaolinite breaks down to produce an amorphous defect oxide phase which is homogeneous and finely porous. When heated at 900°C the reaction product is a defect spinel with strongly preferred orientation and microporous structure. This defect spinel phase is observed in the temperature range 900-1150°C and shows little change in microstructure throughout this temperature range where the secondary development of muUite also occurs to a limited extent. Above 1150°C mullite develops in quantity and appears to represent the bulk of the reaction product at 1200°C.
A Study of Weathering in a Soil Derived from a Biotite-Hornblende Rock
Authors: Wilson M. J.
Published: December 2006

The weathering of biotite in a sedentary soil profile developed on biotitehornblende- rock near Rehiran, Inverness-shire has been investigated by optical, X-ray, chemical, infrared and differential thermal methods. In the C horizon a direct transformation to hydrobiotite was observed. This involves oxidation of all the ferrous iron present and subsequent movement of ferric ions from the octahedral sheet. In the B horizon weathering proceeds to a fully expanded 14A phase and this was identified as interstratified vermiculite-chlorite in a 1:1 ratio. Chemical analysis indicates that this stage is accompanied by a substantial addition of magnesium, much of which goes to form the brucite-like interlayers. In the more acid surface horizon these interlayers tend to break down thus yielding a more vermiculitic product. The possible general implications of this type of biotite weathering are briefly discussed.
Adsorption of Water by Montmorillonite—Poly(Ethylene Glycol) Adsorption Products
Authors: Parfitt R. L. , Greenland D. J.
Published: December 2006

Water adsorption by interlamellar complexes of poly(ethylene glycols) and montmorillonite has been determined using a silica spiral spring, and supplementary data obtained by X-ray and infrared techniques. The adsorbed water enters the interlamellar region, where it is associated with the exchangeable cation. The lattice swells to accommodate the intercalated water. Only weak hydrogen bonds are formed between the surface of the clay and the adsorbed water or between adsorbed PEG molecules and adsorbed water. The presence of PEG did not prevent extensive swelling of sodium montmorillonite.
Kinetics of Alumina Removal from a Calcined Kaolin with Nitric, Sulphuric and Hydrochloric Acids
Authors: Hulbert S. F. , Huff D. E.
Published: December 2006

An investigation of the acid-leaching of a calcined kaolin was made to compare the reaction kinetics of hydrochloric, nitric, and sulphuric acids. The acid concentrations used were 5·9 and 8·6 normal. Reaction temperatures used were 95°, 80° and 60° C.

Particular attention was given to finding a reaction equation which would mathematically represent the kinetic data. A nucleation rate equation of the general form, was found to represent these data. Values of m varied from 1·10 to 1·55 depending on the experimental conditions.

Under the conditions employed the rate of alumina leaching is fastest with hydrochloric acid, slower with sulphuric acid, and slowest with nitric acid. The rate controlling steps are proposed from the experimental evidence.
The Synergetic Effect of Hydrogen Ions on the Cation Exchange of Potassium in Micas
Authors: Newman A. C. D.
Published: December 2006

Interlayer K in eleven trioctahedral micas, with compositions ranging from fluorphlogopite to biotite, was replaced by treating cut flakes with aqueous solutions of Na salts at controlled pH values. Replacement in natural micas was faster at pH 4·5 than at pH 9, and there is a co-operative action or synergy of H+ and Na+ in replacing K+. The synergetic effect of H+ tends to be greatest in micas that lose most net negative charge when K is replaced, and increases when Fe2+ in biotite is oxidized by heating. Possible relationships between the synergetic effect and the chemical composition of micas are discussed in relation to the structure and chemical changes in the aluminosilicate layers when K is exchanged, and it is concluded that incorporation of protons into the structure is responsible for the synergetic effect.
The Intercalation of Polar Organic Compounds into Kaolinite
Authors: Olejnik S. , Posner A. M. , Quirk J. P.
Published: December 2006

The intercalation of several highly polar organic compounds into kaolinite and the formation of interlamellar complexes has been examined by X-ray diffraction. Some compounds intercalate directly into kaolinite, while others can only be intercalated by the displacement of a previously intercalated compound. The formation of the complexes is strongly dependent on the properties of the organic compound, and generally a large dipole moment favours the formation of a complex. A large dipole moment may however cause extensive association in the liquid state and this decreases the rate of intercalation. The addition of water to highly associated compounds increases the rate of intercalation by breaking up the structure of the associated liquid, and the rate passes through a maximum with increasing water content. Thus the rate of intercalation is found to depend on the extent of association in the liquid or solution, the temperature and the molecular size. The d(001) spacings of the complexes are given and the orientation and packing of the intercalated molecules in relation to the Δ - values is discussed.
A Study of Weathering in a Soil Derived from a Biotite-Hornblende Rock
Authors: Wilson M. J. , Farmer V. C.
Published: December 2006

The weathering of hornblende in the Rehiran profile has been investigated by optical, X-ray, infrared and differential thermal methods. Optical studies of the fresh hornblende show that it contains discrete lamellar intergrowths of another amphibole which, from infrared evidence, is of an iron-rich nature. This minor phase is selectively weathered in the lower horizons and yields a clay mineral which was identified as interstratified swelling chlorite-saponite. The major hornblende component remains relatively unchanged. Single crystal photographs indicate that the formation of the clay mineral is not structurally controlled by the parent hornblende, although there is a tendency towards alignment along cleavage planes. The clay mineral becomes unstable in the upper part of the profile and could not be detected in the A horizon. Comparisons are made with the findings of other workers.
A plasticity chart as an aid to the identification and assessment of industrial clays
Authors: Bain J. A.
Published: December 2006

The plastic properties of clays are sufficiently variable to offer a simple but practical aid to identification. This can be done by using their Atterberg 'plastic limit' and 'plasticity index' values as parameters for an identification chart. The advantages and disadvantages of the technique are discussed, and results for a wide variety of clay minerals, particularly industrial clay types, are illustrated. A brief summary is also given of the effect of non-clay impurities, and reference is made to the correlation of Atterberg limit values with other physical properties of clays.
Some applications of thermohygrometric analysis to the study of clay and associated minerals
Authors: Creer M. H. , Hardy J. B. C. , Rooksby H. P. , Still J. E.
Published: December 2006

A new method of measuring the water evolved on thermal dehydration of a variety of clay minerals and related hydrated compounds is described. By placing the substance in a tubular furnace and passing over it a dry inert gas, water released on heating is carried to a sensitive electrolytic hygrometer for measurement. The heating is programmed to give a uniform rate of temperature rise, so that continuous monitoring of the evolved water permits discrimination between successive dehydration processes occurring at different temperatures. The procedure is appropriately termed thermohygrometric analysis (THA).

The applications described include investigations of the thermal decomposition behaviours of hydrated aluminas and hydrated iron oxides, and of clay minerals such as kaolin, montmorillonite, chrysotile and micas. The relations between the results given by thermohygrometric analysis and those obtained by differential thermal analysis are discussed. As with DTA, the record trace from a THA examination gives a graphical representation of the dehydration process, but THA has an advantage in providing a quantitative measurement of the water evolved.
The correspondence between optical and X-ray measurements of particle orientation in clays
Authors: Tchalenko J. S. , Burnett A. D. , Hung J. J.
Published: December 2006

The spatial arrangement of platy particles in a clay is defined by an orientation ratio which can be derived analytically from optical birefringence as well as from X-ray diffraction data. Measurements on kaolin slurries consolidated by increasing loads were used to verify that orientation ratios obtained experimentally by these two methods are in fact equivalent. In contrast it was found that particle orientation cannot be assessed objectively from electronmicrographs alone. A combined optical-X-ray study of two natural clays (London Clay and Lias Clay) revealed that the kaolinite crystals are oriented only slightly more than the illite crystals, and showed that the correspondence between optical and X-ray measurements is also valid for natural clays.
A study of disorder in kaolinite
Authors: Noble F. R.
Published: December 2006

X-ray powder diffraction patterns of kaolinites have been studied with especial reference to the region of the 02, 11, band. Satisfactory correlations with calculated patterns based on the layer structure of dickite can be achieved for a range of kaolinites if account is taken of disorder between and within layers. Some indication of the amount of disorder within a kaolinite can be obtained.
Pyrophyllite-bearing flint clay from the Cambewarra area, New South Wales
Authors: Loughnan F. C. , Ward C. R.
Published: December 2006

A thick deposit of flint clay in the Permian I llawarra Coal Measures of the southern part of the Sydney Basin, New South Wales, is described. The flint clays which have affinities with those of the Pennsylvanian of North America and with the kaolin coal tonsteins of the Westphalian, are associated with red-brown claystones that contain in addition to hematite, an abundance of a regular mixed layer clay mineral. Pyrophyllite generally forms a minor constituent only of the flint clays but in one part of the deposit it is more abundant than kaolinite. Although there are many puzzling aspects concerning the origin of the deposit, evidence suggests that the kaolinite and the pyrophyllite in the flint clays are detrital.
Beidellitic montmorillonite from Swansea, New South Wales
Authors: Hamilton J. D.
Published: December 2006

The minus 1μm fraction of an argillized vitric tuff, overlying the Wallarah Coal Seam near Swansea, N.S.W. is a nearly monomineralic (95%+) expandite clay, which hydrates and reacts to glycerol and heat treatments like montmorillonite. Results of X-ray, differential thermal, thermogravimetric and infrared absorption analyses confirm the general montmorillonoid character of the mineral, but chemical data indicate that much of its structure charge arises from substitutions in the tetrahedral zones of the lattice, as in beidellite rather than montmorillonite. The structural fOrmula deduced for the Ca++-saturated form of the minus 0.1μm clay is:

The distinctive behaviours of the heat-treated NH4+- and Li+-saturated structures also suggest that the mineral is a 'beidellitic montmorillonite' rather than a montmorillonite.
Complexes vermiculite—aminoacides
Authors: Rausell-Colom J. A. , Salvador P. S.
Published: December 2006

Vermiculite single crystals immersed in aminoacid solutions of varying concentration and pH, form complexes characterized by discrete basal spacings. Organic molecules enter in the interlayer space as cations and as dipolar ions through mechanisms of ion exchange and dipole adsorption.

The basal spacings of the complexes were recorded. Based on these results the possible arrangements of the aminoacid molecules have been discussed.The main assumptions used are: (a) the electropositive groups NH3+penetrate into the holes formed by the basal oxygens of the silicate; (13) the C-N bonds are perpendicular to the silicate sheets; (c) the hydrogen atoms of the —CH2 groups are directed towards the sheet surfaces; (d) the —COO−and —COOH groups are located in the middle plane of the interlayer space, halfway between the negative structural charges; and (e) double hydrogen bonds are formed between —COOH groups belonging to organic cations adsorbed onto opposite surfaces.

In solutions of higher concentration the crystals swell to the gel state. This phenomenon is due to: (a) the different nature of interlayer cohesion after substitution of the inorganic cations by the aminoacid cationic form; and (b) the appearance of repulsive forces between —COO−groups of adsorbed dipoles, that overcome cohesive forces.
Complexes of halloysite with organic compounds
Authors: Carr R. M. , Chih Hwa
Published: December 2006

More than twenty new organic complexes of halloysite have been prepared and one hundred and twenty-seven compounds were tested. Results are compared with those of earlier studies and use is made of recent findings concerning particle morphology and interstratification effects to interpret the results. The compounds which form complexes with halloysite are polar, and are usually either acids or bases. Their molecules usually contain two functional groups (preferably —OH and/or —NH2), are relatively small and have one functional group per two carbon atoms, but do not usually include cyclic or aromatic types. The best explanation of the existence of these metastable complexes seems to lie in the ability of some organic molecules to form hydrogen bonds with the halloysite structure, about which insufficient knowledge is available to allow quantitative evaluations to be made.
Partial molal volumes of calcium-montmorillonite
Authors: Ferreiro E. A. , Helmy A. K.
Published: December 2006

Partial molal voltmae of Ca-montmorillonite, apparent molal volume of silica gel in water and of Ca-montmorillonite in ethanol-water mixtures, were determined using pycnometer density measurements. No electrostriction of water was observed with silica gel but took place in Ca-montmorillonite thus indicating the principle role of surface charges in stricting water. In ethanol-water mixtures alcohol molecules were salted out at low alcohol concentration, but they started reaching inner zones near the clay surfaces when their mole fraction in solution was increased beyond the value of 0·55.
The apparent and partial molal volumes of K-montmorillonite
Authors: Ferreiro E. A. , Helmy A. K.
Published: December 2006

The partial and apparent molal volumes of K-bentonite in pure water and in 0·5 M KCl were determined using pycnometer density data. The values obtained were found to increase with particle concentration. Theoretical values of the electrostatic contribution to the volume of particles calculated from an assumed model based on the electric double layer theory, gave values different from those found experimentally. This is explained as due largely to the uncertainties in the value of the clay specific surface area as well as to the assumed ideality of the model used.
Calculated X-ray diffraction profiles for interstratified kaolinite-montmorillonite
Authors: Cradwick P. D. , Wilson M. J.
Published: December 2006

Calculated diffraction profiles for interstratified kaolinite and montmorillonite have been used to determine the composition of clays reported from Poland, Japan and Mexico. The predicted layer proportions determined from the curves and by other methods are in close agreement for the first two but a higher kaolinite content than that originally proposed is obtained for the Mexican clays.
Some problems encountered in the identification of plumbogummite minerals in soils
Authors: Campbell A. S. , Adams J. A. , Howarth D. T.
Published: December 2006

The use of HF digestion to concentrate minerals of the plumbogummite group is discussed. Prolonged treatment is shown to result in solution of plumbogummite minerals, and in precipitation of HCl-insoluble, complex fluorides. These yield X-ray diffraction spacings that may be confused with those of plumbogummite minerals. The presence of fluorides in digestion residues is confirmed by X-ray diffraction, DTA and by identifying the products formed when such residues are heated to 600°C.
An Electron Microscope Study of Magnesium Smectite Synthesis
Authors: Baird T. , Cairns-Smith A. G. , Mackenzie D. W.
Published: December 2006

The synthesis of magnesium smectite from heated slurries of magnesium hydroxide, silica and lithium fluoride proceeds through ready formation of torroidal structures visible under the electron microscope. These are associated with the synthesis of a smectite-like material with, however, only half the expected requirement for silica. True smectite only forms significantly with Si/Mg ratios > 1 and reaction times (at reflux) > 1-3 days.
A Rapid Method for the Determination of Quartz in Sedimentary Rocks by X-Ray Diffraction Incorporating Mass Absorption Correction
Authors: Cosgrove M. E. , Sulaiman A. M. A.
Published: December 2006

An X-ray diffraction method for the estimation of quartz is described using rock powder pellets originally prepared for X-ray spectrometry, correcting the X-ray intensities for mass absorption. A coefficient of variation of 3·8% is claimed; 95% of all estimates fall within ± 5·5%.
An Unusual Chlorite as Revealed by the High Temperature X-Ray Diffractometer
Authors: Kimbara K. , Shimoda S. , Sudo T.
Published: December 2006

An unusual chlorite has been collected from amygdales in Miocene volcanic rock found at Taiheizan, Akita Prefecture, Japan. The mineral shows subtle variations from other chlorites and related minerals. These are: (a) no apparent expansion with water or ethylene glycol, (b) negligible or no collapse after NH4-saturation or heating at about 300°C, (c) a slow decrease in the basal spacing on heating from approximately 400°C to 760°C, (d) a small amount of low temperature or capillary water and (e) a DTA curve with a vermiculite-like system of peaks.

The mineral is identified as a highly chloritic vermiculite with a small proportion of imperfect hydroxy interlayer.
An interstratified illite-smectite from Denchworth series soil in weathered Oxford Clay
Authors: Weir A. H. , Rayner J. H.
Published: December 2006

The very fine (<0·04 µm) clay fraction of a Denchworth series subsoil in weathered Oxford Clay has been investigated in detail. It contains a layer silicate mineral, almost free from impurities, that is a randomly interstratified mixture of approximately 45% expanding and 55% non-expanding interlayers with the following unit formula: Na0.33K0.29(Al1.41Fe0.34Mg0.26)(Si3.60Al0.40)O11. Computer-simulated diffraction patterns showed that experimental patterns are best matched when an average diffracting packet consists of between 4 and 5 2:1 layer silicate units. Correction of the chemical composition for external exchangeable ions associated with such small packets gives non-expanding interlayers a charge density of 0·69K/Si4O11 and expanding interlayers one of 0·57M+/Si4O11. The relationship between these values and those of mica and regularly expanding minerals is briefly discussed.