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.

Minerals with the general formula Cu4(OH)6A2/nn ± pH2O (A = Cl–, NO3–, SO42–) were synthesized and their behaviour following treatment with chloride, nitrate and sulfate solutions was studied by powder XRD and SEM. Two types of transformation were found: (1) an ion-exchange reaction manifested by preservation of both the precursor's morphology and structural type; (2) a dissolution-crystallization mechanism characterized by changes in the structural type and the morphology.

The results were considered by simultaneous application of the binary presentation of the structures, a bond valence approach and the ion-exchange ability. It was found that the structures of minerals with ion-exchange properties are built from similar layered structural unit of edge-shared and corner-shared Jahn-Teller square frameworks and different interstitial complexes of exchangeable ions, water molecules and cation-water groups. On the basis of their structural features the position of the investigated minerals in mineralogical classifications is also discussed.

Five montmorillonites were analysed by 57Fe Mössbauer spectroscopy and their Fe3+ occupation in tetrahedral and octahedral sites assigned. The montmorillonites, with a range of IVFe3+ contents, were used in an attempt to correlate IVFe3+ content with VIFe3+cis- and trans-OH site occupation to verify the assertion that increasing IVFe3+ content directs VIFe3+ to cis-OH sites. However, VIFe3+ in montmorillonite appears to be located essentially in the trans-OH sites. The two doublets computer-fitted to the VIFe3+ Mössbauer resonance for montmorillonite appear to represent a distribution of a continuum of slightly different Fe3+ resonances, which arise from the variable atomic environment surrounding the VIFe3+ sites, rather than discrete cis- and trans-OH sites. Therefore Mössbauer spectroscopy cannot be used to demonstrate whether an increasing IVFe3+ content directs VIFe3+ substitution into particular sites for montmorillonites.

Reservoir description is achieved by the integration of geological, petrophysical and engineering data. Modelling of reservoir performance is made by creating a three-dimensional model of the reservoir volume, where the reservoir is built of cells and layered zones which are defined geologically. Although the scale of cell size is coarse compared to the scale of geological data, it is important that the geological input to define cells is as precise as possible. The texture of clay minerals and their composition are requisite for understanding their influence on reservoir characteristics. Wireline logs probably do not provide sufficient information about clay mineralogy to evaluate reservoir characteristics, but do allow the extrapolation of ‘point’ mineralogical data into a continuous reservoir description. Evaluation of porosity, permeability and saturation are described, and the possible influence of clay mineralogy on evaluation of these characteristics is discussed.

Clay and glauconite fractions separated from sedimentary rocks in Israel were analysed for their mineralogical composition by X-ray diffraction and dated by the K-Ar method. The main goal was to evaluate early diagenetic processes which might have affected the K-Ar system. One series of samples was taken from two contemporaneous mid-Albian to mid-Turonian (~105–91 Ma) shallow marine successions in which early diagenetic K-feldspar was found to be widespread. Another series was of samples of large spatial distribution associated with a mid- Turonian emergence event. None of the outcrops had been subjected to high temperatures due to deep burial or other thermal events. The abundant clay minerals in the first series are randomly ordered illite-smectite (I-S) phases of various discrete and mixed compositions. Illite, kaolinite, ordered I-S and palygorskite are sometimes present. The variability in clay assemblages and I-S composition within short vertical distances and the proximity to the provenance implies mostly a detrital origin for the clay minerals. The K-Ar ages of clay fractions in the first series are no older than 30% of the stratigraphie ages, much younger than the known detritus provenance ages. A few have known stratigraphie ages and one is younger by 10%. The K-Ar ages of associated glauconite fractions are younger by 5–13% than the stratigraphie ages. The ages of the clay fractions of the second series, which are on average more illitic, are mostly younger and no older than 22% more than the stratigraphie age. The age distribution and the clay mineralogy in the two series suggests that illitization of detrital I-S phases may start right after deposition under specific conditions, namely, contact of the sediments with K-rich brines, produced by evaporation in restricted marine environments. The process may continue from a few to many millions of years after burial, as long as K-enriched solutions are available. However, in most cases the near-surface temperatures did not enable a completion of the K-Ar reset process. It seems that low-temperature illitization is better explained as being dependent on solution composition and not on wetting-drying cycles.

Sorption of an acidic, amphoteric, sulphur containing and basic α-amino-acid (glutamic acid, glycine, methionine and lysine) by copper montmorillonite was studied by chemical and X-ray methods. With glutamic acid complex formation occurs only in solution but increasing basicity of the aminoacid favours complex formation in the clay interlayers.

The use of electron microscopy to study clay microfabrics in thin-sections is discussed. A technique is described to isolate undisturbed microparts of pedofeatures from thin-sections, which are subsequently used for TEM analysis. Re-embedding with a polyester resin of undisturbed, in situ, neoformed clay microfabrics, obtained by microdrilling and preparation of ultrathin sections by microtoming with a diamond knife are emphasized; these steps enable micromorphology, clay mineralogy, microchemical and HRTEM analysis to be performed on one unique microsample of clay fabrics, with conserved micro-organization. Two examples on clay neoformation are presented to demonstrate that this technique can successfully be applied to unravel the impact of mineral alteration and clay neoformation in undisturbed soil samples on a micro- and a nanometer scale.

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

Veins of intimately associated fibrous and granular saponitic clay occur in a basalt quarry at Orrock, Fife, Scotland. Preliminary X-ray diffraction studies suggested that both fibrous and granular forms consisted of pure saponite but chemical and thermal studies showed the presence of subsidiary amounts of interstratified chlorite. The fibrous clay, which is strongly oriented around the a axis but with a uniform distribution of the b and c poles, consists mainly of highly-crystalline laths with minor amounts of turbostratically-ordered particles. The granular clay consists of turbostratically-ordered particles only. The swelling behaviour of both types of clay in water and in ethylene glycol is similar to that of pure saponite. With glycerol, only the granular clay swells completely but the fibrous clay behaves similarly if first subjected to grinding or chemical pre-treatment. These observations are accounted for on the basis that the fibrous clay has better order than the granular form, thus enabling the interlamellar constituents to participate more fully in layer-to-layer bonding.

Accessory green ferric clay occurs in fluvial litharenites of the Early Triassic Rewan Group. Although resembling glauconitic minerals in thin-section, electron microprobe analyses indicate that the green ferric clay is mainly ferric illite. The ferric illite may have formed in a small hypersaline lake or well drained, flood-plain soil, and its presence in the Rewan Group cannot be used to support a notion that the unit is partly marine influenced. Identification of the ferric illite by electron microprobe analysis shows that some green ferric clays, particularly those that resemble glauconitic minerals optically, may require precise quantitative elemental analysis before they can be used as a basis for environmental interpretation. Green ferric clay in the Rewan Group also includes detrital celadonite that most likely originated in a volcanic arc setting.

The general effect of grinding upon various minerals and the manner in which time of grinding affects cation-exchange capacity, etc., have been known for some time, but relatively little information is available upon the micas (Jackson and Truog, 1939; Kelley and Jenny, 1946; Parkert et al., 1950; Mackenzie and Milne, 1953). This, coupled with an observation made here on the pronounced effect of short-period grinding on muscovite, has led to a more detailed examination of the effects induced by such grinding upon some micas. Since the data for muscovite are completely discussed elsewhere (Mackenzie and Milne, 1953) only preliminary experiments upon biotite and vermiculite are recorded here.

The regional distribution, mineralogy, petrology and chemistry of the detrital and authigenic clay minerals associated with the Permo-Triassic strata (excluding the Rotliegend: see Ziegler, 2006; this volume), of the onshore and offshore regions of the British Isles are reviewed within their stratigraphical framework. The origin of these clay minerals is discussed in relation to current hypotheses on the developments of the Mg-rich clay mineral assemblages associated with the evaporitic red-bed Germanic facies of Europe and North Africa.

Composite clay mineral successions are described for seven regions of the British Isles — the Western Approaches Trough; SW England; South Midlands; Central Midlands; the Cheshire Basin; NE Yorkshire; and the Central North Sea. The detrital clay mineral assemblages of the Early Permian strata are variable, consisting of mica, smectite, smectite-mica, kaolin and chlorite, whereas those of the Late Permian and the Trias are dominated by mica, usually in association with minor Fe-rich chlorite. The detrital mica consists of a mixture of penecontemporaneous ferric mica, probably of pedogenic origin, and recycled Pre-Permian mica. In the youngest Triassic strata (Rhaetian), the detrital clay assemblages may contain appreciable amounts of poorly defined collapsible minerals (irregular mixed-layer smectite-mica-vermiculite) and kaolin, giving them a Jurassic aspect. There are two types of authigenic clay mineral assemblages. Kaolin may occur as a late-stage diagenetic mineral where the original Permo-Triassic porewaters of the sediment have been replaced by meteoritic waters. A suite of early-stage diagenetic clay minerals, many of them Mg-rich, are linked to the evaporitic red-bed facies — these include sepiolite, palygorskite, smectite, irregular mixed- layer smectite-mica and smectite-chlorite, corrensite, chlorite and glauconite (sensu lato). The sandstones and mudstones of the onshore regions of the British Isles display little or no difference in their detrital and authigenic clay mineral assemblages. In contrast, the sandstones of the offshore regions (North Sea) show major differences with the presence of extensive chloritic cements containing Mg-rich and Al-rich chlorite, irregular mixed-layer serpentine-chlorite, and mica.

Polycyclic aromatic hydrocarbons are increasingly widespread pollutants introduced into the environment via oil spillage and incomplete anthropogenic combustion of fossil fuels. In this work, the capacity of stevensite and sepiolite to adsorb phenanthrene (PHE) has been evaluated experimentally by batch testing. Both clay minerals are distributed widely in the Madrid Basin, are of low cost and can be applied with minimal environmental impact. In the context of few previous studies, adsorption isotherms have been developed to understand the adsorption mechanisms and were fitted to the Freundlich and linear models with virtually the same results. Although stevensite showed greater adsorption capacity than sepiolite, the isotherms were constructed for equilibrium concentrations up to 0.8–1.0 mg/L due to the low solubility of PHE in water. When compared to other adsorbents the ability of stevensite to retain PAHs should be examined further in order to add and complement novel functions in reactive barriers.

The thermal dehydration of a series of smectites has been investigated by X-ray methods. It has been found that the rate of collapse of the layers is governed by the type of exchangeable ion present.

The high temperature changes of a new saponite have been investigated. The saponite dehydrates to talc and then to enstatite, the 5·2Å fibre axis remaining constant throughout.

Transmission electron microscope-analytical electron microscope analyses have been carried out on secondary minerals from pillow basalts with various degrees of alteration from the Juan de Fuca Ridge (ODP Leg 168). The electron microscopic data indicate that the alteration products consist mainly of phyllosilicate mixtures. The least altered sample shows poorly crystalline phyllosilicates occurrring as flakes with 10 Å -spaced lattice fringes. They have compositions of celadonite mixed with smectite and/or Fe oxyhydroxides and Mg-rich smectite. Proceeding towards older, more altered basalts, the alteration products consist of: (1) poorly crystalline celadonite mixtures and Mg-rich smectite; and (2) phyllosilicates with a higher degree of crystallinity, showing lattice fringes with 9.1 Å -spacing and with a talc-like composition. Changes in phyllosilicate association occur as the type of alteration changes from an oxidizing, water-dominated system (occurrence of celadonite mixtures with Fe hydroxides) to a reducing, rock-dominated system (occurrence of Fe-smectite and talc-like mixtures).

The kieselguhrs or diatomaceous earths are composed essentially of more or less well crystallised silica, as well as a small quantity of alumina, iron oxide, and traces of other oxides. These earths are largely used as filtration aids; they can serve as supports for certain catalysts, and have also excellent calorifugic properties.

A study of different sorts of kieselguhrs used as supports for nickel and cobalt catalysts in the Fischer-Tropfsch synthesis has recently been carried out by Anderson et al. (1947). These authors find that a previous treatment of the raw kieselguhr by hot hydrochloric and nitric acids gives more active catalysts than those obtained using the same support untreated, and especially than those prepared from calcined kieselguhrs.

From this investigation it was hoped to obtain information about the position of the exchangeable cations. That they take up a position between the layers of the mineral seems obvious from the varying c spacing of dried montmorillonite saturated with different ions, but in the complexes with water and organic liquids it was not known whether the ions remained close to the layers or were removed from them. It was also hoped that the Fourier syntheses would give some information about the actual layer structure of the mineral (montmorillonite) and thereby lend support to one of the two suggested structures, those of Hofmann, EndeU and Wilm on the one hand and of Edelman and Favejee on the other.

The montmorillonite used was a sample of Wyoming bentonite separated on the Sharples supercentrifuge. In order to get as large a contrast as possible between the two syntheses it was decided to use Li+-saturated montmorillonite and Ti+-saturated montmorillonite.

In the region of Illapel, Chile, dioritic and andesitic rocks of Cretaceous to Paleocene age from the Unidad San Lorenzo Formation have suffered strong alteration resulting in the formation of a kaolin-rich zone, which is mined in the La Vanguardia open pit near Combarbalá. Detailed mineralogical and chemical investigations of channel samples from this mine, involving a combination of optical microscopy, XRD, SEM-EDX, XRF and TEM, permitted recognition of a zone of silicification and a zone of advanced argillic alteration, both of which contain alunite s.s. and aluminium-phosphate-sulphate (APS) minerals of the woodhouseite group with subordinate amounts of gorceixite, florencite and goyazite. These minerals are found to have originated from infiltration of meteoric waters. The passage from silicification into advanced argillic alteration was associated with an increase in sulphate activity as manifested by the increase of SO42— at the expense of PO43— in the alunite s.s. and by an increase of the Au content from 0.01 to 0.03 mg/kg Au. This high sulphidation type of wallrock alteration may be roughly compared with the Nansatu type of White (1991).

The term ferrihydrite, originally defined as a poorly ordered hydrous ferric oxide exhibiting five or more distinctive X-ray diffraction maxima, has come to be extended to include species that exhibit only 4, 3 or 2 of these maxima. It is pointed out here that hisingerites may exhibit a similar 2-line diffraction pattern. The laboratory synthesis of hisingerites show that they can form under soil conditions. Acid oxalate buffer of pH 3, a reagent considered a fairly specific solvent for ferrihydrite, extracts the iron content of these synthetic hisingerites quantitatively.

L'étude de l'adsorption des acides fulviques, des acides humiques ou de leur mélange par la montmorillonite saturée avec du calcium ou de l'aluminium permet de: (i) définir les mécanismes de fixation des substances humiques en phase aqueuse; (ii) préciser une orientation différente des moécules adsorbées selon leur nature; acides fulviques ou acides humiques; (iii) caractériser une forte sélectivité d'adsorption pour les molécules les moins polymérisées.

A partir de ces résultats, il est montré que, d'une part, la flexibilité des molécules est un paramètre important pour les propriétés de sélectivité et, d'autre part, les acides humiques ne peuvent pas être considérés en équilibre avec les acides fulviques.