bluuebunny/crossref_metadata_2025_split huggingface dataset:
Chlorite clay minerals in Ordovician pumice-tuff and derived soils in Snowdonia, North Wales
Authors: Ball D. F. 
Published: December 2006

AbstractCalcareous 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

AbstractThe 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.
A study of a long-spacing mica-like mineral
Authors: Cole W. F. 
Published: December 2006

AbstractAn 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

AbstractDi- 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 reaction4Fe2+ + 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

AbstractThe 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.
Clay minerals and geomorphology in four Caribbean islands
Authors: Beaven P. J. , Dumbleton M. J. 
Published: December 2006

AbstractClay 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

AbstractThe 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

AbstractA 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 formulaK0.90Ca0.06Na0.49[Al3.52, Fe0.183+Mg0.27Ti0.03(Al1.24Si6.76) O20(OH)4] H2OIt 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

AbstractThree 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

AbstractThe 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

AbstractWhen 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

AbstractThe 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

AbstractA 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

AbstractThe 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

AbstractThe 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

AbstractA 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

AbstractAn 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.
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.
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.
Electron Optical Study of the Thermal Decomposition of Kaolinite
Authors: McConnell J. D. C. , Fleet S. G. 
Published: December 2006

AbstractThe 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

AbstractThe 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

AbstractWater 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

AbstractAn 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

AbstractInterlayer 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.