bluuebunny/crossref_metadata_2025 huggingface dataset:
Flocculation of Na-montmorillonite by electrolytes
Authors: Ferreiro E. A. , Helmy A. K.
Published: December 2006

The flocculation of a Na-montmorillonite suspension by Na, Ca, and Al chlorides was investigated using the optical absorbance method. The flocculation of the clay was found to be irreversible with a degree of irreversibility that increases with electrolyte concentration. The flocculation values of Na, Ca and Al chlorides were found to be equal to 8, 0·25 and 0·032 mmol/l respectively. The ratio of the flocculation values of the different salts is in reasonable agreement with the ratio predicted by current theories of colloid stability.
The point of zero charge (pzc) of kaolinite and SiO2+AI2O3 mixtures
Authors: Tschapek M. , Tcheichvili L. , Wasowski C.
Published: December 2006

The pzc of H+-kaolins determined by titration method is nearly pH = 3. The pzc of SiO2 + Al2O3 mixtures is not additive, and depends principally on Al2O3 content in mixture. The curve pzc—t°C (t°C = temperature of treatment of kaolins) has two maxima: 4·7 after treatment at 800-900°C, and 5 after treatment at 1300°C.
Selective dissolution and formula derivation of clay vermiculite from some Tuscan soils
Authors: Ristori G. G. , Cecconi S. , Vidrich V. , Pacifici G.
Published: December 2006

The chemical composition and structural characteristics of clays from samples of eight Tuscan soils were investigated. Using simple selective dissolution method (successive boiling in 1 N HCl and 0·5 N NaOH) it was possible to distinguish two types of low charge dioctahedral vermiculite; one easily HCl soluble the other practically insoluble.

Structural formulae for the soluble type were calculated from the chemical analysis of the dissolved material; for the insoluble type it was possible to calculate only an 'average' structural formula which included the micaceous material.

Since the HCl soluble vermiculites show a high content of Fe and Mg, they can be considered either as alteration products of glauconites or biotites, or as a result of a synthesis, at least in soils derived from basic rocks which do not contain mica.

The aluminous insoluble type, present also in parent material, may be the result of an incomplete 'illitization' in a marine environment.
Maghemite in soils and its origin
Authors: Taylor R. M. , Schwertmann U.
Published: December 2006

A magnetic iron oxide is a common constituent of ferruginous concretions in highly weathered Australian soils and is generally associated with varying proportions of hematite and occasionally with goethite. The X-ray diffraction pattern and the low Fe (11) contents (4-15% of total Fe) of this magnetic phase identify it as maghemite which was further confirmed by IR and DTA. This maghemite is only slightly soluble in dithionite but readily in 1:1 HCl or oxalic acid. From the Fe (11) contents and mineralogical associations in soil concretions, conditions for maghemite formation under near pedogenic conditions are suggested.
Electron spin resonance in natural kaolinites containing Fe3+ and other transition metal ions
Authors: Meads R. E. , Malden P. J.
Published: December 2006

A number of natural kaolinites from a variety of world sources have been investigated using electron spin resonance at both X-band and Q-band. The results show systematic differences some of which are related to the crystallinity of the material, some to the presence of transition metal ions other than Fe3+ and hole-trapping defects.

The results provide evidence for at least three sites for substitution of Fe3+ having large crystal fields : (i) a site with near maximum rhombic character having crystal field parameters D > 1·2, λ = ⅓ the occurrence of which is correlated with lack of crystalline perfection due to stacking defects or to the proximity of surfaces, (ii) a site with less rhombic character with λ = 0·234, D = 0·585 as likely parameters, and (iii) a site with parameters near the values λ = 0·207, D = 0·322.

Mössbauer and ESR evidence suggests that the principal sites of Fe3+ substitution are octahedral. The presence of Fe3+ in adjacent cation sites leads to a very broad resonance centred near geff = 2. Other resonances in the spectra are attributed to the effect of trapped holes, some at least of which are situated at oxygen sites adjacent to Al3+ ions substituting in sites normally occupied by Si4+.

Hyperfine effects due to the presence of the transition ions Mn2+ and (VO)2+ are also observed.
On the calculation of one-dimensional X-ray scattering from interstratified material
Authors: Cradwick P. D.
Published: December 2006

A method is given for calculation of X-ray scattering from interstratified materials which is applicable to components that do not possess centres of symmetry. This procedure allows contributions from interlamellar material to be included in the calculation without any assumptions being imposed by the method on the composition of the components. The method is in fact a simplification of the general formula given by Kakinoki & Komura (1965).
Surface properties of mixed Cu(II)—tetraalkylammonium montmorillonites
Authors: McBride M. B. , Mortland M. M.
Published: December 2006

Initial exchange of Cu(II)-montmorillonite by tetrapropylammonium (TPA) or tetramethylammonium (TMA) ions results in segregation of different ions in randomly interstratified layers, with particular preference for TPA over Cu(II) during exchange. More complete exchange reverses this preference and both Cu(II)-TPA and Cu(II)-TMA clays become more homogeneous. The copper ions of the homogeneous Cu(II)-TPA clays are not fully hydrated while the TMA ions have less effect than TPA on the hydration of copper, probably a result of the smaller radius and higher hydration energy of TMA. Methods of X-ray diffraction, thermogravimetric analysis, BET surface area determinations, as well as infrared and electron spin resonance spectroscopy, are used in supplying evidence of cation distribution and hydration properties of these clays. Definite changes in the properties of hydrated copper when associated with tetraalkylammonium ions on the clay surface are indicated.
Synthesis of kaolinite by homogeneous precipitation at room temperature
Authors: La Iglesia A. , Martin-Vivaldi J. L.
Published: December 2006

A method of precipitation in homogenous solution has been used for the synthesis of kaolin minerals at room temperature. The method consists essentially in producing conditions for which a sufficiently slow rate of precipitation is maintained. In the particular case described in this paper, the conditions for homogenous precipitation are obtained by addition of an anion exchange resin in the OH form to an acidic solution (pH ≈ 4) of sodium silicate and aluminium chloride or acetate.

The mineral species synthesized in each particular case depend on the kind of anions present in the original solution (chloride or acetate) and also on the nature of the exchange resin used.
A method for measuring the mineralogical variation of spoils from British collieries
Authors: Collins R. J.
Published: December 2006

A semi-quantitative mineralogical analysis of colliery spoil by XRD has been developed and used to compare spoils from eight collieries, in connection with work on the production of synthetic dense aggregates from spoil. Phase analysis of clay, which constitutes over half of all these spoils, is carried out by comparing X-ray peak areas of oriented specimens after heating and treatment with ethylene glycol. Total clay is obtained by difference, after determination of quartz and other minerals by an internal standard technique, allowing calculation of the proportion of each clay mineral. The results are tested against chemical analysis and a semiquantitative X-ray analysis of the chlorite present indicated that it is a highly ferruginous variety. Differences are detected in the mineralogy of all eight spoils but, except for the predominance of kaolinite in the spoils from Scotland, these differences are small.
An unusual weathered profile from Orange, N.S.W., Australia
Authors: Bayliss Peter
Published: December 2006

Samples were collected from a 11·4 m deep weathered profile of a metamorphic rock. The mineralogy was determined from XRD powder patterns, differential thermal and thermogravimetric analyses with CEC determinations and chemical analyses.

Four stages in a weathering sequence from the profile base towards the surface are as follows : (i) a partially regular trioctahedral chlorite-chlorite mixed layer ; (ii) a random chlorite-vermiculite mixed layer; (iii) a random chlorite-smectite mixed layer, and finally (iv) a smectite. Some chloritic layers are therefore more resistant to chemical weathering than other chloritic layers. This profile indicates that the order of decreasing resistance to chemical weathering is talc > smectite > tremolite.
Hydratation des smectites et demixtion des cations Li, Na en fonction de la localisation des substitutions isomorphiques
Authors: Glaeser R. , Fripiat J. J.
Published: December 2006

Par l'étude de la variation de la charge réticulaire relative et de la surface spécifique relative, accessible à l'eau, de smectites ayant subì l'effet Hofmann-Klemen à différents degrés, on montre que celles caractérisées par des substitutions tétraédriques (Beidellite B de Rupsroth et Ascan-gel) se différencient clairement de l'Ascan-argile qui ne contient que des substitutions en couche octaédrique. Dans la beidellite, la démixtion des cations Li, Na est totale pour toutes les compositions de la garniture cationique tandis que la démixtion n'apparaìt dans le cas de la montmorillonite que si (Na+/Li+) < 0·75. L'Ascan-gel occupe une position intermédiaire. Ces observations sont interprétées comme une indication que les substitutions tétraédriques empèchent l'expansion des feuillets en suspension.
Use of flocculated fraction of calcareous soil suspensions after ultrasonic treatment for mineralogical study
Authors: Heakal M. S. , Herbillon A. J.
Published: December 2006

Separation of the clay fraction from a calcareous soil usually involves chemical pretreatments which could affect the separated clays. A technique based on separating the flocculated particles (flocs) of a sonified soil-water suspension was used on highly calcareous samples and a highly gypseous one collected from a limestone ridge in Egypt. The relative abundance of the clay minerals in flocs (identified by XRD and electron microscopy) was found to be identical to that of < 1 μm clay separated by sedimentation. The suspensions were prepared by washing the soils repeatedly with distilled water (about 2 1/g) until spontaneous peptization.

Washing removed both 'amorphous' silica and alumina as detected in the flocs. The composition of poorly-ordered aluminosilicates (SiO2/Al2O3) of the 1μm clays was heterogeneous whereas in the flocs it was homogeneous.

Fluoride reactivity of both clay separates and prepared mixtures of CaCO3 with palygorskite (the dominant clay mineral present) was also studied.
Amorphous ferri-aluminosilicates in some tropical ferruginous soils
Authors: Krishna Murti G. S. R. , Sarma V. A. K. , Rengasamy P.
Published: December 2006

The amorphous mineral selectively dissolved from the clay (<2 μm) fractions of twenty-six ferruginous soils contains considerable iron in addition to silicon and aluminium. SiO2/Al2O3 and SiO2/R2O3 molar ratios are between 2·03-3·52 and 1·72-2·95 respectively. The model of the amorphous ferri-aluminosilicate (AFAS) consists mainly of negatively charged tetrahedrally coordinated silica-alumina phase Si3AlO6(OH)4 containing domains of neutral FeOOH, with an outer positively charged hydroxyaluminium polymeric component [Al(OH)2.5]n.The calculated hydroxyl water content of the AFAS averages 17·8%; cation exchange capacity varies from 48·6 to 112·0 mEq/100 g and shows a negative correlation with the outer hydroxyaluminium octahedral component and a positive correlation with the ratio of the tetrahedral Si-Al component to the octahedral hydroxyaluminium component. The K-fixation capacity (1·9-6·1 mEq/100 g) of the AFAS does not appear to be related to the chemical composition. The genesis of the amorphous mineral is discussed.
A Mössbauer study of the weathering of hornblende
Authors: Goodman B. A. , Wilson M. J.
Published: December 2006

The behaviour of iron in the natural weathering of hornblende in a sedentary soil profile has been investigated using the Mòssbauer effect. The spectra from samples at different stages of weathering show appreciable differences which can be accounted for if ferrous iron is lost preferentially from M(3) sites where it is coordinated to hydroxyl groups in a trans arrangement. Unlike biotite the proportion of ferric iron does not increase during weathering and this illustrates the difficulty with which the ferrous iron is oxidized in the amphibole structure.
Problems in layer-charge determination of montmorillonites
Authors: Lagaly G. , Fernandez Gonzalez M. , Weiss Armin
Published: December 2006

Spanish montmorillonites from Frente Archidona were used to demonstrate the determination of charge density, CEC and, in mixtures, the montmorillonite content by the aikylammonium method. Special attention is directed to heterogeneous montmorillonites and the determination of the charge density distribution. Some problems which arise by application of the method are discussed: relations between layer charge and cation densities, particle size corrections, microstructures and unsymmetric charge distributions in the interlayer spaces.
The Influence of [Fe(II)], [Si], and pH on the formation of lepidocrocite and ferrihydrite during oxidation of aqueous FeCl2 solutions
Authors: Schwertmann U. , Thalmann H.
Published: December 2006

Lepidocrocite was synthesized from the oxidation of FeCl2 solutions with and without soluble Si and at various Fe(II) concentrations and pH. Pure well crystallized lepidocrocite was only obtained if CO2 was excluded (to prevent goethite formation) and if pH was kept between 5 and 7 (to prevent maghemite and ferrihydrite formation). Si in solution prevented crystallization of lepidocrocite with increasing Si/Fe atomic ratio (varied between 0 and 0·156) and at the same ratio with decreasing pH. Most of the Si added is probably included in the lepidocrocite and ferrihydrite structure (up to 4·4% Si) and these Si contents are linearly correlated with the initial Si/Fe ratio. No indication from XRD and i.r. spectroscopy was found for changes in the lepidocrocite structure due to Si uptake. The ferrihydrite containing 4·35% Si showed a broad Si-O-stretching vibration which in contrast to pure silica (1080 cm−1) is shifted to lower frequencies (940 cm−1) indicating some Si-O-Fe bonds.
Iron in kaolinite with special reference to kaolinite from tropical soils
Authors: Herbillon A. J. , Mestdagh M. M. , Vielvoye L. , Derouane E. G.
Published: December 2006

The location of iron in five deferrated soil kaolinites and several reference samples has been investigated using chemical analyses, acid dissolution and electron paramagnetic resonance spectroscopy.

The iron of most of the kaolinites can be divided into a 'structural iron' content, measured by the amount of iron, dissolved at the same rate as aluminium by acid attack, and a 'resistant iron' content, which is concentrated with the residues.

Integration of the geff~4 resonance bands of the electron paramagnetic resonance (EPR) spectra allows a semiquantitative estimate of the 'structural iron' in the samples. A multiple relationship seems to exist between the crystallinity index, the 'structural iron' content and the shape and intensity of both geff~4 and geff~2 EPR signals. The tropical soil kaolinites are a peculiar category with a high content of iron (>2% structural Fe2O3) fire-clay kaolinite, low crystallinity and a specific EPR spectrum exhibiting strong geff~4 resonance bands and no or weak geff~2 sharp doublet.
Beidelltie clay from Chang-yuan, Taiwan; geology and mineralogy
Authors: Chen Pei-Yuan , Wan Hsien-Ming , Brindley G. W.
Published: December 2006

Beidellite clays near Chang-yuan, 80 km south of Hwalien, form vein-like bodies 5-10 m wide and 20-45 m deep. Andesitic rocks have been fractured by faulting permitting hydrothermal solutions to percolate and produce an altered mineral assemblage in which beidellite is associated with a mixed-layer illite-smectite, kaolinite, dusty pyrite, microquartz, cristobalite, calcite and dolomite, plagioclase, and gypsum. Ca-clay is common on outcrops and subsurface, where the clay is leached, Na-clay is found; some outcrops are partly kaolinized. Chemical analyses of the beidellite show that the structure is charged predominantly in the tetrahedral sheets. Exchange capacities are mainly in the range 120-140 mEq/100 g clay (110°C); exchangeable cations are Na ≫ Ca ≃ Mg > K. After K saturation and heating, ten samples still expand to near 17 A with ethylene glycol, but the two samples with the highest tetrahedral charge expand only to 14·6-15·0 Å although their total charge is similar to the other samples.
Influencia de la materia organica en la genesis de gibsita y caolinita en suelos graniticos del centro-oeste de España
Authors: Gallardo Lancho J. , Sanchez Camazano M. , Saavedra Alonso J. , Garcia Sanchez Y. A.
Published: December 2006

Tornando corno base las conclusiones obtenidas en trabajos anteriores sobre las variables significativas en la genesis de gibsita bajo clima templado, se han seleccionado cinco perfiles de alteration de granitos. En esas condiciones los datos termodinàmicos indican que este mineral no puede originarse nunca por un proceso de hidrólisis tipicamente inorgànica. El mecanismo propuesto, complejación del aluminio con àcidos fùlvicos y posterior evolución a gibsita, se muestra corno el mas probable. Se sugiere también que està gibsita puede combinarse con silice para dar lugar a caolinita. Ambos minerales, pues, tienen un posible origen esencialmente orgànico. Este hecho explica la vinculación caolinita y/o gibsita con determinados tipos de vegetación.
Kernmagnetische resonanzmessungen an Glaukoniten
Authors: Kohler Ewald E. , Burkert P.K.
Published: December 2006

Bei der Untersuchung von 6 Glaukonitproben mit Hilfe der ‘H-Kernresonanz-Spektroskopie zeigen sich deutlich zwei verschieden gebundene OH-Gruppierungen. Wàhrend die relativ scharfen Signale A auf die in der Oktaederschicht flxierten zwei OH-Gruppen zuriickzufuhren sind, muB fiir die anderen OH-Gruppen des breiteren Signals B eine andere Bindungsnatur gefordert werden. Es ist móglich, dafl es sich bei den OH-Gruppen des Signals B ebenfalls um verschieden gebundene OH-Gruppen handelt und zwar um solche, die an Eisenhydroxid- Verunreinigungen gebunden sind und solche, die zwischenschichtlich in Form von Eisen-Hydroxo-Komplexen gebunden sind. Eine Unterscheidung zwischen letzteren beiden Mòglichkeiten ist aber nicht mòglich.
Influence of uniformly dispersed mineralizers on firing and mechanical resistance of clay ceramics
Authors: Lemaitre J. , Bulens M. , Delmon B.
Published: December 2006

Some parameters of the firing of kaolin around 900°C are examined: (1) firing shrinkage; (2) densification, hardening and textural evolution of kaolin ceramics. Experimental results are accounted for by an empirical formula describing the isotherm firing shrinkage of kaolin ceramics.

Depending on the precursor salt added, the spreading and dispersion of the mineralizer is more or less homogeneous. If, during thermal decomposition, the salt induces much porosity, this effect can counterbalance the shrinkage caused by the mineralizer. The kinetics of shrinkage, and the final density after firing depend both on the latter effects and on the mineralizer cation. A very good correlation is observed between shrinkage, final density (residual pore volume) and the strength of the fired clay product. The introduction of uniformly dispersed mineralizers causes an increase in mechanical resistance (for identical temperatures and firing times) by a factor greater than 3, occasionally 5) and, for equal firing times and mechanical strengths, lowers the firing temperature by 100-200°C.
The 14 Å phase developed in heated dickites
Authors: Brindley G. W. , Wan Hsien-Ming
Published: December 2006

Dickites with well-ordered crystal structures and with relatively high dehydroxylation temperatures develop a 14 Å phase when heated to temperatures in the range 550–800°C. The actual spacing is close to 13·7–13·8 Å. Dickites with less well-ordered structures and with lower dehydration temperatures give less development of this phase or none at all. Other kaolinite group minerals do not produce a similar phase. Thermal weight-change and differential thermal analysis data show that the 14 Å phase develops to a maximum as hydroxyl ions are eliminated from the dickite structure and infrared spectroscopic data are consistent with this result. AIKα fluorescence wavelength measurements indicate that the Al ions are in four-fold coordination in the 14 Å phase. Absence of other diffraction data makes structure analysis impossible. The description ‘chlorite-like’ for the 14 Å phase is of questionable validity.
Zur Mineralogie, Kristallchemie und Geochemie einiger Montmorillonite aus Bentoniten
Authors: Vogt Klaus , Köster Heinrich M.
Published: December 2006

Dioktaedrische Smektite aus 19 Bentonitproben werden abgetrennt. Aus den chemischen Analysen errechnen sich unter Berücksichtigung der direkt gemessenen Zwischenschichtladungen (nach Lagaly & Weiss, 1971) kristallchemische Strukturformeln von exakt dioktaedrischen Mineralen. Die Tetraederzentren in der Struktur sind fast ausschliesslich von Si4+ besetzt; nur zwei der untersuchten Minerale zeigen eine beidellitische Komponente. Die gemessenen mittleren Zwischenschichtladungen der Montmorillonite (0·33 bis 0·39) ergeben sich allein aus der oktaedrischen Substitution von Me3+ durch Me2+. Im Gegensatz zu der grossen Variation der Strukturformeln von dioktaedrischen Smektiten in der älteren Literatur sind die kristallchemischen Unterschiede der hier untersuchten gereinigten Smektite sehr klein.

Im Vergleich zu den Rohbentoniten sind die Konzentrationen der meisten Spurenelemente in den abgetrennten Montmorilloniten erheblich verringert. Nur Mn, Zn, Co und Ni scheinen in die Kristallstruktur eingebaut zu sein. Die übrigen analysierten Spurenelemente sind adsorbtiv gebunden oder in akzessorischen Mineralen enthalten.
Chemistry and mineralogy of some Lower and Middle Chalks from Givendale, East Yorkshire
Authors: Pitman J. I.
Published: December 2006

The chemical composition of nine samples of Lower and Middle Chalk from the Givendale area of Yorkshire was determined; acetic acid residues were mechanically, chemically and mineralogically analysed. All nine chalk samples proved to be exceptionally pure calcium carbonate (96±1·5%), with only small amounts of MgO (1·03±0·53%), Al2O2 (0·33±0·28%) and Fe2O2 (0·20±0·14%). Insoluble residues ranged from 1·07 to 4·46%. Clay formed 56–88% of the insoluble residue. The non-clay fraction consisted of flint, quartz, collophane, limonite, feldspar, tourmaline and zircon. The clay fractions were dominated by montmorillonite (50%) with secondary illite (30%), apatite (3%), and quartz (8–30%). Kaolinite was detected by X-ray diffraction in the Lower Chalk.
Silicifications and associated clay assemblages in the cretaceous marine sediments of southern england
Authors: Jeans C. V.
Published: December 2006

Silicifications and smectite-dominated clay assemblages are associated in the marine Cretaceous sediments of England. Both are neoformed, and have developed at approximately the same time in the host sediment. Two silicification types, opal-CT and α-quartz, have a distribution pattern unrelated to the stratigraphy or lithology of the Lower Greensand, Upper Greensand and Lower Chalk. The petrography of five examples suggest that the two silicification types were both precipitated from the porewaters of their host sediment, and their silica mineralogy and their associated silicate minerals were controlled generally by the silica concentration of the porewaters and more locally by the pH gradients.
Formation et applications de complexes mica-vermiculite-chlorure de sodium
Authors: Le Dred R. , Wey R.
Published: December 2006

Un minéral interstratifié mica-vermiculite en paillettes de 1 à 4 mm2 est traité par des solutions concentrées de chlorure de sodium. Dans ces conditions une adsorption de sel dans les interfeuillets vermiculite se superpose à l'échange d'ions. L'adsorption de sel prédomine en solution concentrée et l'échange d'ions en solution moins concentrée. Des complexes salins sont ainsi obtenus. Ceux-ci possèdent la propriété de gonfler macroscopiquement dans l'eau avec désorption du sel. L'addition d'eau oxygénée aux solutions salines provoque également un gonflement. Cette propriété est utilisée pour la transformation du minéral en vermiculite. Le minéral et la vermiculite gonflés trouvent des applications intéressantes.
Formation de complexes mica-vermiculite-halogenure de metal alcalin
Authors: Le Dred R. , Wey R.
Published: December 2006

La mise en contact d'un minéral interstrafié mica-vermiculite, en paillettes de 1 à 4 mm2, avec une solution concentrée d'halogénure de métal alcalin conduit à un échange d'ions ainsi qu'à une adsorption de sel. L'échange d'ions n'est que partiel et l'adsorption de sel a lieu dans les interfeuillets vermiculite. La teneur du minéral en sel adsorbé dépend de la nature du cation et de l'anion du sel ainsi que de la température de la solution. Les complexes salins obtenus possèdent la propriété de gonfler macroscopiquement dans l'eau avec désorption du sel. Dans les cas des chlorures de lithium, de potassium et d'ammonium, les complexes salins tendent vers des compositions définies.
Diagenesis of illite in argillaceous sediments of the Rhinegraben
Authors: Heling D.
Published: December 2006

The diagenesis of illite from smectite was investigated in relation to temperature on marly shale core samples from different Tertiary stages (depths between 200 and 3000 m) by X-ray and chemical analyses. It is concluded that the alteration of smectite to illite primarily depends on the cumulative energy supply (temperature × time). Small grain size and high potassium concentrations in the pore solutions shorten the time necessary to complete the alteration. Potassium is supplied by decomposition of feldspar within the sediment so that the replacement of feldspar by secondary calcite increases the availability of potassium. Supply of potassium by pore solutions from distant sources is very unlikely due to reduced permeability in compacted shales. Illite diagenesis is influenced by the inherited layer charge of the initial smectite.
Imogolite and proto-imogolite in an Italian soil developed on volcanic ash
Authors: Farmer V. C. , Fraser A. R. , Tait J. M. , Palmieri F. , Violante P. , Nakai M. , Yoshinaga N.
Published: December 2006

Imogolite has been identified in small amounts in clays from a soil profile developed on pyroclastics of tephrite-bassanite composition. The major part of the fine clay was an allophanic material termed proto-imogolite, characterized by an infrared spectrum with some of the features given by imogolite, including a well-developed band at 346 cm−1. Similar products have been obtained in the laboratory.
Infra red and electron spin resonance studies of clays representative of the sedimentary evolution of the Basin of Autun
Authors: Elsass F. , Olivier D.
Published: December 2006

Three samples have been selected to represent the sedimentary variations of the Basin of Autun. IR and ESR techniques have been used to study the sheet composition of the different kinds of clays. The kaolinites are fire clays with two different degrees of crystallinity. The illites have a muscovite origin and belong to the 1 M polytype with mainly tetrahedral Al3+ and Fe3+ substitutions but also with some octahedral Fe3+ substitutions. The dioctahedral phyllosilicates contain mostly divalent and trivalent octahedral substitutions.
Reactivity of a long-spacing ammonium-propionate-kaolinite intercalate toward diol, diamines and quaternary ammonium salts
Authors: Seto H. , Cruz-Cumplido M. I. , Fripiat J. J.
Published: December 2006

This paper describes reactions occurring between the 25.5 Å ammonium propionate (AP) intercalate of a well-crystallized Georgia kaolinite with ethylene glycol, 1-6-diaminohexane and a quaternary amine (QA), namely

An ethylene glycol kaolinite complex is obtained with a strong d001 reflection at 10.9 Å. Seven 00l orders are observed easily. The IR spectrum shows bands at 3697, 3654 (weak shoulder) 3644 and 3622 cm−1, assigned to OH stretching of kaolinite and a strong OH band of E.G. at 3300 cm−1. No absorption band of AP is observed.

The 1.6-diaminohexane product is characterized by two broad reflections at 16.6 and 7.4 Å. Distinct Amide I and Amide II IR bands imply that the carboxyl group of the propionic acid has reacted with the amino group. By treating the AP complex with QA a very stable kaolinite-QA complex suspension in benzene was obtained. On drying an X-ray amorphous solid with no reflection at spacing & 20 Å was obtained. The hydroxyl stretching bands of the original kaolinite are drastically modified, a very strong band at 3560 cm−1, a strong doublet at 3620 and 3605 cm−1 were observed. A weak singlet is obtained at 3695 cm−1. The two OH bending bands are replaced by a single band at 912 cm−1. A complicated set of interactions results in the loss of stacking order about the C-axis, accompanied by some curling of layer packets. A prolonged treatment with water restores the X-ray and IR spectra of the original kaolinite.
Efecto de la deshidratacion sobre las propiedades adsorbentes de la palygorskita y sepiolita
Authors: Fernandez Alvárez T.
Published: December 2006

Se estudia el efecto de la deshidratación sobre la superficie especifica y distribución del tamaño de poro en sepiolita y palygorskita. Se emplean las técnicas de A.T.D., A.T.G., adsorción-desorción de nitrógeno y microscopía electrónica.

La eliminación del agua higroscópico-zeolitica incrementa en los dos minerales la superficie especifica y la proporción de microporos accesibles a las moléculas de nitrógeno.

Con la pérdida del agua de cristalización disminuye, en ambos minerales, la superficie especifica y la proporción de los citados microporos, desapareciendo los de anchura inferior a 7 Å en las próximidades de la eliminación completa de esta clase de agua.

La eliminación del agua de constitución origina neuvos descensos de la superficie especifica en la sepiolita de acuerdo con las alteraciones sufridas, puestas de manifesto en al análisis térmico; más acusadas que en la palygorskita.
The reaction of ammonia with vermiculite and hydrobiotite
Authors: Stone M. H. , Wild A.
Published: December 2006

The reaction of ammonia with Mg-saturated vermiculite and hydrobiotite was studied by chemical analysis, X-ray diffraction, and differential thermal analysis, and the hydrobiotite also by infrared spectroscopy. The experimental evidence indicates that ammonia is adsorbed mainly as the ammonium ion, formed partly by reaction with interlayer water and partly by reaction with protons dissociated from octahedral layer hydroxyl groups, giving a single sheet of ions and molecules with irregular interlayer spacing. With large flakes (0.5–1.0 mm) the adsorbed ammonia is strongly retained on heating or on rehydration with water vapour: smaller flakes lose ammonia more readily. Ammonia uptake is related quantitatively to cation exchange capacity with two vermiculites and three hydrobiotites, and to the water content prior to adsorption.

Na-saturated vermiculite adsorbs a similar amount of ammonia to the Mg form, but it is mostly desorbed on rehydration. Cu-saturated vermiculite displays intermediate behaviour, with much of the ammonia initially present as a Cu-ammine which slowly reacts to give more ammonium ion.
A chemical investigation of a chlorite intergrade mineral in the Keuper Marl
Authors: MacNeill S.
Published: December 2006

An extensive X-ray diffraction investigation of Keuper Marl samples from the English Midlands shows the existence of both chloritic and interlayered chloritic clays.

Chemical experiments show that the interlayer component of the chloritic phase can be removed. This suggests that the ‘chloritic materials of unusual type’, known since the early 1950s to exist in the Keuper Marl, represent chlorite-montmorillonite intergrades.

The mineralogy of any sample identified by an X-ray investigator, is influenced by the completeness of the chlorite interlayer. Since the amount of interlayer material is variable any ‘absolute’ differentiation between species is difficult.
Evolution of surface area in a sepiolite as a function of acid and heat treatments
Authors: Jiménez-López A. , López-González J. de D. , Ramīrez-Sāenz A. , Rodrīguez-Reinoso F. , Valenzuela-Calahorro C. , Zurita-Herrera L.
Published: December 2006

The variations in surface area of a sepiolite (Toledo, Spain) after acid and heat treatments (1 n to 5 n, HNO3, 110°C to 900°C for 100 h) have been studied. Surface areas have been determined from N2 adsorption isotherms at 77 K using B.E.T., Langmuir and Dubinin-Radushkevich equations. SBET values range from 65 up to 391 m2 g−1, the maximum value corresponding to the sample activated with 1 n HNO3 solution and treated at 300°C. SL and SD-R values are similar, but slightly larger than the corresponding SBET values.

A correlated study has been carried out with samples activated with 1 n and 2 n HNO3 solutions and heat treated at 110, 200, 300, 400 and 500°C for 10 h. SBET values of these samples are rather similar to those of the corresponding samples treated during 100 h.
The effects of experimental conditions on the 950°C kaolinite exotherm in some tropical soil clays
Authors: Hughes J. C.
Published: December 2006

Some predominantly kaolinitic tropical soil clays when examined by DTA in a nitrogen atmosphere gave two exothermic reactions (at ∼880°C and ∼950°C) instead of the usual single exotherm. During heating, iron present in the samples is reduced, possibly by organic carbon, and reacts with the metakaolin phase to form hercynite (FeAl2O4). The presence of Fe2+ also causes mullite to form at a lower temperature than normal. These reactions accompany the lower-temperature exotherm. The higher-temperature exotherm is due to formation of γ-alumina. Although this exothermic doublet is an artifact of the experimental conditions, its occurrence may help to elucidate the sequence of reactions involved in the metakaolinite recrystallization process.
A contribution to the study of the stability of clay minerals from the soil solution composition at different pF values
Authors: Fernandez-Marcos M. L. , Macías F. , Guitián-Ojea F.
Published: December 2006

The composition of the soil solution of various horizons of Galician soils was studied to gain insight into the direction of the processes of weathering and neoformation by means of stability diagrams of the clay minerals. The soil solution was extracted by compression at various pF values.

The most significant results are as follows. In all the cases studied the mineral in equilibrium with the soil solution is a 1:1 philosilicate. As the pF at which the soil solution is extracted increases, corresponding to smaller pore size, pH increases and silica concentration falls. The stable mineral does not vary significantly between different horizons of the same profile. Each parent material gives rise to a different zonation in the stability diagrams. The predictions of the stability diagrams are in general agreement with the mineralogical data of the clays of the horizons in question.

Finally, weathering processes in Galicia are briefly commented on.
Occurrence of chloritic intergrades in the Recent sediments of the Arno River (Italy)
Authors: Sartori F. , Riffaldi R. , Levi-Minzi R.
Published: December 2006

Clay mineral assemblages from a Quaternary sequence, sampled near the estuary of the Arno River, commonly contain some intergrade minerals, associated with other 14 Å phases and with illite and subordinate amounts of a kaolin mineral. The X-ray diffraction characteristics of such intergrade phases and their thermal modifications (100–600°C) are analysed and described.

The effectiveness of some chemical treatments for removal of interlayer material is investigated and the results discussed on the basis of X-ray diffraction pattern and C.E.C. changes. Finally the properties of these intergrades are compared with those of the 14 Å phases present in the sediments carried by the Arno River and its tributary the Era River as well as with those of a soil from the Era watershed. Hypotheses are expressed about the probable relationships between degree of chloritization and characteristics of the depositional environments.
Origine et signification des zéolites dans les dépôts Cénomaniens de la bordure Sud-Est Du Massif Armoricain
Authors: Louail J.
Published: December 2006

Des zéolites de la famille Heulandite-Clinoptilolite se rencontrent dans toute la série cénomanienne littorale péri-armoricaine dans des faciès pétrographiques variés. Souvent présentes à l'étal de traces, leur abondance apparait liée à certaines conditions pétrogénétiques qui peuvent se réaliser localement à diverses périodes mais se généralisent au Cénomanien supérieur provoquant une régionalisation de la ‘paragenèse’: Clinoptilolite, Smectites, Cristobalite.

L'étude au microscope pétrographique et au microscope à balayage des échantillons les plus riches montre que la clinoptilolite se présente en cristaux automorphes dans des pores de dissolution intrasédimentaire. Son origine diagénétique est ici évidente; elle est postérieure à la dissolution des spicules de spongiaires et antérieure à la genèse de certaines sphérules de cristobalite. Ces néoformations se réalisent à partir des solutions interstitielles alimentées, au moins en partie, par l'altération de spicules de spongiaires, feldspaths détritiques, paillettes de mica, glauconie ...

L'origine détritique de la clinoptilolite des sédiments crétacés de la bordure occidentale du bassin de Paris qui avait été envisagée doit donc être écartée; deplús la paragenèse zéolitesmectites-cristobalite ne peut ici être utilisée comme l'indice d'une activité volcanique en cours de dépôt. Une partie des smectites, qui remplit certains pores de dissolution, prend également naissance par diagenèse précoce.
The role of structural iron(III) in the UV absorption by smectites
Authors: Chen Y. , Shaked D. , Banin A.
Published: December 2006

UV-visible light absorption spectra of dilute suspensions of standard and commercial montmorillonites (bentonites) and of nontronite, hectorite and pyrophyllite, were studied.

All montmorillonites exhibit either an absorption band or a shoulder at a wavelength of 245 nm. The absorption peak for nontronite is shifted to 260 nm and absorption intensity is very high. Hectorite exhibits a very slight shoulder whereas pyrophyllite shows almost none. Absorption intensity in the UV range was found to be in direct correlation to structural octahedral Fe(III) contents. Direct evidence for the role of Fe(III) in the specific UV absorption of smectites was obtained by the fact that reduction with hydrazine fumes resulted in the disappearance of the peak and reoxidation with H2O2 caused its reappearance with even stronger intensity than originally. Mössbauer spectra showed that the Fe(III) disappeared almost completely in the reduced clay.
The stability, free energy and heat of formation of imogolite
Authors: Farmer V. C. , Smith B. F. L. , Tait J. M.
Published: December 2006

From equilibrium silica concentrations over imogolite and boehmite at 100–155°C, the heat and free energy of the reaction (HO)3Al2O3SiOH + H2O ⇌ 2AlOOH + Si(OH)4 have been obtained: ΔH°r (298·15 K)=38·6 ± 4·1, ΔG°r (298·15 K) = 26.8 ± 1·1 kJ mol−1, and hence the heat and free energy of formation of imogolite: ΔH°f (298·15 K) = −3189·6 ± 4·1, ΔG°f (298·15 K) = − 2926·7 ± 1·1 kJ mol−1 These results are consistent with observations indicating that imogolite, halloysite and gibbsite can co-exist in soils, but that imogolite is metastable relative to either halloysite or gibbsite in the long term. At temperatures above 25°C there is a widening range of silica concentrations in which imogolite is more stable than halloysite, although both are metastable relative to kaolinite.
Quelques donnees sur la capacite calorifique et les proprietes de l'eau dans divers systemes poreux
Authors: Eger I. , Cruz-Cumplido M. I. , Fripiat J. J.
Published: December 2006

L'eau présente dans les divers types de pores que contiennent des solides divisés a été étudiée par calorimétrie à balayage entre 200 et 270° K et sa chaleur spécifique a été mesurée entre 100 et 260° K. Les solides étudiés sont des argiles de la famille des smectites, l'endellite, des zéolites et une opale.

Les informations obtenues à l'aide de ces techniques sont comparées à celles dérivées d'autres techniques notamment la résonance magnétique nucléaire et la spectroscopie infra-rouge.

Des différences intéressantes sont observées entre des agrégats tri et bidimensionnels de molécules d'eau.
Application de mesures de conductivite hydraulique a l'etude de la structure des gels d'argile
Authors: Prost R.
Published: December 2006

L'étude de la conductivité hydraulique sous de faibles charges de pâtes et de gels d'hectorite-Na, montre que:

1.

La loi de Darcy peut être appliquée,

2.

Le rayon hydraulique moyen qui est probablement relié à la distance moyenne entre les particules d'hectorite varie linéairement avec la teneur en eau et est très sensible à la présence d'électrolyte dans la suspension.
A soil vermiculite formed from a meta-gabbro, Loire-Atlantique, France
Authors: Ildefonse P. , Copin E. , Velde B.
Published: December 2006

Microprobe and atomic absorption analyses of large vermiculite crystals present in the upper horizon of a weathering profile on gabbro show that they differ appreciably in chemical composition. This together with the lack of any phyllosilicate precursor of comparable grain size, strongly suggests that the vermiculites were formed by precipitation of dissolved silicate matter, higher in the profile the vermiculite becomes unstable and is replaced by an Fe-rich smectite.
Rare earth elements in different size fractions of a marine quick clay from Ullensaker, and a till from Upper Numedal, Norway
Authors: Roaldset Elen
Published: December 2006

The distribution of rare earth elements (REE) in two different sediments, a marine clay and a till, was found to be dependent both on grain size and mineralogical composition. In the marine clay the REE content was highest in the coarsest fraction; in the till REE were markedly enriched in the finest fraction. Detrital and authigenic origins for different size fractions have been attributed on the basis of REE contents.
Natural and synthetic poorly crystallized lepidocrocite
Authors: Schwertmann U. , Taylor R. M.
Published: December 2006

Poorly crystallized lepidocrocites precipitated from ferriferous spring waters differ from better crystallized samples by differentially broadened X-ray diffraction lines and higher basal spacings. On the basis of high magnification EM, this was explained as due to the fact that the lath-like crystals consist only of 3–15 unit layers with possibly weakened H-bonding between the layers. These properties are analogous to those of the so called ‘pseudoboehmite’ as compared to boehmite. Poorly crystallized lepidocrocites, exhibiting similar features, were synthesized by oxidation of Fe(II) solutions. From these experiments it was suggested that such lepidocrocite forms in nature by a rapid oxidation of Fe2+ in spring water when it emerges at the surface.
Iron in kaolinite: II. The relationship between kaolinite crystallinity and iron content
Authors: Mestdagh M. M. , Vielvoye L. , Herbillon A. J.
Published: December 2006

Calibration of the internal and external signals appearing at geff ∼4 in the electron paramagnetic resonance (EPR) spectra of twenty-four kaolinites, has led to the recognition of two types of kaolinite-iron. The amount of iron associated with the internal signal (I iron) shows good inverse correlations with parameters used to describe the degree of crystalline perfection in kaolinite. Iron associated with the external signal (E iron) is insensitive to crystalline order. By considering both the amount and nature of the iron, the kaolinites investigated are placed in three groups. The first contains well-crystallized varieties characterized by low total iron and EPR spectra consisting mainly of an E signal. Poorly-crystallized kaolinites contain more iron and are characterized by a fifty-fifty partition of this iron into E and I sites. The third group contains samples which are intermediate with respect to both the amount and nature of the iron.
Transient fluorescence studies on sepiolite suspensions
Authors: Ridler P. J. , Jennings B. R.
Published: December 2006

Measurements have been made of the transient changes in the polarized components of fluorescence when aqueous suspensions of dye-tagged sepiolite particles were subjected to pulses of high frequency alternating electric field. The dye was acridine orange, a planar, cationic molecule. From these measurements, the size and electrical prolarizability of the sepiolite particles was evaluated and the directions of the absorption and emission transition moments responsible for the fluorescence of the dye located. The dye molecules were shown to adsorb on the clay surface with their long axes parallel to the sepiolite rods. Adsorption of the dye molecules in the surface channels of the clay was indicated. The electrical polarizability was considered and compared with the cation exchange capacity of the mineral. A novel, rapid means of studying clay minerals is indicated hereby.
Mineralogical composition of the clay fraction of two fluvio-glacial sediments from east Greenland
Authors: Petersen L. , Rasmussen K.
Published: December 2006

The < 2µm fractions of two fluvio-glacial sediments from East Greenland have been analysed chemically and by XRD and Mössbauer spectroscopy. The bulk of each < 2µm fraction consists of feldspars and micas (biotite) which are important constituents of the Precambrian igneous and metamorphic rocks of the area. Significant amounts of vermiculitic and smectitic minerals are also present. Compared with similar minerals present in Danish soil clays, the Greenland vermiculite and smectite are characterized by a high degree of crystallinity and it is concluded that these minerals have been formed from biotite through K release and lattice expansion. These processes appear to have proceeded at a sufficiently high rate to yield significant amounts of vermiculite and smectite despite the cold climate prevailing in the area.
Facteurs determinant la structure de la couche interlamellaire des vermiculites saturees par des cations divalents
Authors: Alcover J-F. , Gatineau L.
Published: December 2006

L'organisation de l'espace interlamellaire des vermiculites a été comparée en fonction: (i) de la nature du cation (Mg, Ni, Ca, Sr et Ba) et de son état d'hydratation (bicouche, monocouche et anhydre), (ii) de la nature du feuillet (charge et localisation des substitutions). Le facteur prépondérant, celui qui confère à l'espace interlamellaire son caractère ordonné ou non, est la nature du cation en particulier sa taille et son degré d'hydratation. La charge du feuillet apparaît comme un facteur complémentaire, elle limite la taille des domaines ordonnés.
Single-crystal X-ray study of mixed structures of vermiculite and biotite (hydrobiotites)
Authors: Weiss Zdeněk
Published: December 2006

The Weissenberg method has been used to study crystalline fragments of hydrobiotites from Stupná near Křemže, Czechoslovakia. The intensity distribution for basal reflections recorded in zero-level photographs indicates that most ‘single crystals’ are nearly regular interstratifications of vermiculite and biotite. Proportions of vermiculite in these interstratifications lie between 12 and 60%.