A scanning and transmission electron microscopy study has been performed on Oligocene glacio-marine sediments, Devonian sandstones, and Jurassic dolerites recovered during CRP-3 drilling in the Ross Sea (Antarctica). Newly formed clay minerals occur in the rock matrices and as fillings in veins and faults which crosscut the whole sequence. Authigenic clays in sediments consist of beidellite-montmorillonite, berthierine/chlorite intergrowths and illite. Al,K-rich smectites and kaolinite occur in the Devonian sandstones. Saponite, berthierine/chlorite intergrowths, and Fe-hydroxides develop in the altered dolerites. Hence, the composition of the secondary phases depends also on the geochemistry of the rock they grow in. Within each sample, the same authigenic minerals form in the matrix and in the vein/fault. Clays precipitated from fluids, with variable fO2 values, which circulated in the system during the contemporaneous diagenetic and faulting events.

Clays from the Saïss basin (northern Morocco) used traditionally in the ceramic industry in the Fez area were studied using mineralogical and physicochemical techniques to evaluate their potential suitability as raw materials for ceramics manufacture. X-ray diffraction was used to determine their mineralogical composition. The physical properties determined were particle-size distribution and consistency limits. The chemical composition was determined using X-ray fluorescence analysis and Fourier-transform infrared spectrometry. The structural changes of the mineral phases in the raw materials during firing were studied over a temperature range of 500–1000°C. In the pottery site from Fez, generally potters use a mixture of 25% fine clay (ARFS) from the upper part of the Miocene marls and 75% sandy clay (ARFR) from the lower part of the Miocene marls. The ARFS clay yielded very rigid specimens after firing that artisan potters would find difficult to handle so as to produce desired shapes and sizes. However, the specimens obtained from ARFR clay show signs of faltering. The mixture of these two clayey materials from this pottery site is therefore necessary to obtain the optimal paste for ceramics purposes. The chemical compositions indicated that SiO2, Al2O3, CaO and Fe2O3 are the major minerals, with trace amounts of K2O and MgO. Quartz, feldspars and clay minerals prevail in all samples. Kaolinite, illite and smectite are the dominant clay mineral phases, with traces of chlorite and interstratified illite–smectite. The classification of these samples using appropriate ternary diagrams showed that the proportions used in the mixture produce a new material with adequate characteristics for the production of traditional ceramics.

The interaction between a basic dye, rhodamine B, and a separated fine fraction from natural clay was studied. Chemical analysis, X-ray diffraction and Fourier-transform infrared spectroscopy confirmed the predominance of beidellite in the fine clay fraction. The interaction of rhodamine B with the fine clay fraction showed that sorption was fast and followed a pseudo-second-order kinetic model. The comparison between sorbed rhodamine B amounts as a function of the various experimental parameters such as pH, sorbent mass, dye concentration and the presence of competing ions suggests that: (1) the sorption process is largely pH-dependent; (2) significant competition is observed between the dye and the Ca2+ and Mg2+ ions; (3) the sorption proceeds, principally, by a cation-exchange mechanism; and (4) the sorption capacity of the fine fraction in the presence of competing cations such as Ca2+ is ~0.28 mmol g–1.

The stability of a shale containing smectite with different exchangeable cations (Na+, Ca2+) was improved using optimum solutions containing polyether amine (PA), poly-alcohol (PO) or KCl. Two types of shale samples with Na+ and Ca2+ as the main exchangeable cations, respectively, were used and the optimized solutions were determined using X-ray diffraction (XRD), an adsorption test, an oedometer swelling test, and an immersion test. The use of KCl prevented intercalation of PA or PO and maintained the stability of the Na-smectite-bearing shale. PA or PO adsorption reduced water adsorption sites on the clay layer, and K+ reduced hydration of exchangeable Na+, resulting in good shale stability in mixed solutions of KCl+PA, and KCl+PO. More stable shale was achieved in KCl+ PA mixed solution, whereas in the KCl+ PO solution the transport of water or solute molecules in the shale was reduced. In the shale containing mainly Ca-smectite, PA, PO and KCl maintained shale stability when applied separately or in common, as PA or PO cannot exchange Ca2+ in the smectite interlayer. As a result, PA or PO should be used together with KCl during drilling in shale formations containing Na-smectite, whereas in shales with Ca-smectite, PA, PO or KCl may be used separately.

More than 100 minerals have been reported from the Silver Coin Mine, Nevada USA; five new minerals have been discovered here, due to the unusual geochemical environment. The present study reports on the investigation of a greenish clayey sample from the Silver Coin Mine. After the separation of a fine fraction to enrich the clay minerals, sauconite, a rare Zn-rich smectite, was found by X-ray diffraction (XRD) and was further characterized by differential thermal analysis (DTA), infrared (IR) spectroscopy and scanning electron microscopy (SEM). The Zn-rich smectite is accompanied by illite, minor kaolinite/halloysite and traces of gibbsite (as was indicated by the IR spectroscopy). The occurrence indicates an acidic environment probably caused by oxidation of sulfides.

The determination of the structural formula, to further characterize the Zn-rich smectite, was difficult because of the multi-clay mineral assembly. However, different SEM-EDX (energy dispersive X-ray) approaches as well as transmission electron microscopy (TEM)-EDX analysis helped to characterize the smectite as Al-rich sauconite with some exchangeable K+.

Because of widespread tremolite and chrysotile minerals in Palaeozoic-Mesozoic metamorphic and Triassic ophiolitic units, respectively, in the Eskişehir region, Turkey, there is significant potential for development of cases of mesothelioma. Such occurrences in the Eskişehir region show a positive correlation with the concentration and dimension of tremolite crystals compared with those of chrysotile crystals. A detailed assessment of the mineralogy, geochemistry and genesis of these materials has not been carried out to date; the present study was undertaken to fill that gap. The sharp diagnostic basal reflections at 8.14 Å, 3.09 Å and at 7.30 Å, 3.63 Å, well defined fibrous crystallinity, and ideal differential thermal analysis-thermal gravimetric and Raman curves suggest the development of well crystallized fibrous/acicular tremolite and chrysotile with the average structural formulae of: (Na0.07K0.03)(Ca1.68Mg0.18Mn0.01)(Fe0.42Mg4.55Ti0.01)(Si7.60Al0.24Fe0.16)O22(OH)2, and (Mg5.55Fe0.41 Mn0.006)(Si3.79Al0.13)O10(OH)8, respectively.

Enrichment of light rare earth elements relative to medium rare earth elements and heavy rare earth elements in tremolite compared to that of chrysotile which exhibits no anomaly and negative anomalies for Ba, Sr, Ce, Nb, Yand Zr in the tremolite samples and chrysotile, are responses to the fractionation of feldspar, glaucophane, pyroxene and olivine under the high temperatures of hydrothermal-alteration processes during serpentinization and the high-pressure conditions of metamorphism. Based on H and O isotope data, the tremolite and chrysotile are thought to have developed from tectonically controlled magmatic and meteoric hydrothermal systems and the formation temperatures of the tremolite are higher than those of chrysotile.

Montmorillonite (Mnt), a clay mineral with a nanolayered structure, was combined with an Fe-based metal–organic framework (MOF; MIL-53(Fe)) using an in situ growth technique that yielded a novel eco-friendly clay-based adsorbent (MIL-53(Fe)@Mnt). The adsorbent was characterized by scanning electron microscopy, Fourier-transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis and N2 gas adsorption. The MIL-53(Fe) particles grew on the surface of the nanolayered Mnt and the MIL-53(Fe) particle size became smaller. The adsorption performance of MIL-53(Fe)@Mnt was investigated by removing methylene blue (MB), and optimization experiments were carried out to study the effects of contact time, pH, initial dye concentration and adsorbent mass on the adsorption processes. The MIL-53(Fe)@Mnt exhibited excellent adsorption capacity for MB, namely 313.7 mg g−1, which was 3.02 times and 3.54 times greater than that of pure Mnt and MIL-53(Fe), respectively. Adsorption was fitted with the Langmuir isotherm model and followed a pseudo-second order kinetic model. The MIL-53(Fe)@Mnt obtained is a low-cost and eco-friendly adsorbing material and might be a candidate for removing dyes during water treatment.

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.

The subarkosic-sublitharenitic Upper Cretaceous sandstone, which has up to 30% porosity and 585 md permeability, produces on salt diapir structures in the Oguendjo West Block, offshore Gabon. The porosity consists of 68% intergranular porosity of primary and secondary origin, 17% secondary intragranular and moldic porosity, and 15% microporosity. A microcrystalline quartz druse, which was derived from alteration of lithic fragments, coats framework grains and retards the development of syntaxial quartz overgrowths. Other cements are patchy ankerite (0·3–13·7 vol%) and kaolinite, which also occurs as a replacement of framework grains. The total kaolinite content ranges from 1·8 to 8·2 vol%. Kaolinite and remnants of altered and partially dissolved lithic fragments are susceptible to movement with fluid flow. Formation sensitivity tests showed that the kaolinite-rich sandstone was stable to 2% NaCl water, but introduction of freshwater caused permeability impairment. Acid treatment to remove damage produced sporadic results. Injection of HCl raised the permeability temporarily, indicating that fines were still being liberated within the pore network. Injection of HCl/HF immediately reduced permeability through partial disaggregation of the rock. Plugging of the formation face by drill mud also damages the reservoir. Reversal of flow at high pressure differentials will remove formation damage produced by face plugging. A guideline for this process established in the laboratory is to backflow with a pressure differential at least as high as the overbalance used in drilling. The combination of oil-based drilling fluids and underbalanced perforating with filtered diesel in the wellbore should eliminate most formation damage in this reservoir.

The chemical equilibrium of a purified sample of hectorite was studied over a range of pH, silicic acid, and magnesium chloride concentrations. The quasi-equilibrium reached by about 6 weeks was reversible with respect to added magnesium ions but only partially so for added silicic acid. The free energy of formation of hectorite at 25° C was calculated at −2680 kcal/unit cell, using the derived equilibrium constant and the stoichiometry of the reaction as previously established.

There is interest in exploiting and developing natural resources, particularly deposits of natural clays. Senegal has several clay mineral deposits for which chemical and mineralogical compositions have been little studied. Some of these natural materials are nowadays used in pottery and ceramics. To extend applications, a better basic knowledge is required and, for this objective, the raw clay and separated <2 μm clay fraction from Keur Saër (Senegal) were subjected to chemical and mineralogical studies. Several techniques including X-ray diffraction (XRD), thermal analysis (TG-DTA), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), N2 adsorption-desorption isotherms, cation exchange capacity (CEC) measurements and solid state nuclear magnetic resonance (NMR) have been used to characterize the material. It was found that the raw clay and the separated clay fraction consist of a mineral mixture in which kaolinite is the main component. 29Si and 27Al MAS-NMR spectra show the presence of silicon atoms linked to three other silicon atoms via an oxygen atom and six coordinated Al atoms. Significant increases in the specific surface area and cation exchange capacity were observed on purification, reaching a maximum of about 73.2 m2g–1 and 9.5 meq/100 g for the separated fine clay fraction while the values for the raw material were around 28.9 m2g–1 and 7.3 meq/100 g.

Ferric oxides or hydroxides are common minor components of kaolinites. If free, these minerals can be removed by Fe reduction and leaching (Mehra & Jackson, 1960), but Fe3+ ions can substitute for Al3+ ions in the octahedral sites of kaolinite (Weaver et al., 1967; Malden & Meads, 1967). Moreover, Fe2+ ions can also substitute trioctahedrally in place of dioctahedral Al, leading to a local composition of Fe-antigorite (Cuttler, 1980).

The Font-Bouillant quarry (Charentes, France) is the source of disordered kaolinite known as ‘FU7, U-7-10 or FBT’ (Cases et al., 1982, 1986). The samples used in this study were considered in an earlier genetic analysis of the deposit (Delineau, 1994; Delineau et al., 1994) and were analysed previously by X-ray diffraction (XRD), infrared (IR) spectroscopy, electron paramagnetic resonance (EPR) and UV-visible spectroscopy by Delineau et al. (1994) (Table 1).

L'altération de biotites et de muscovites en halloysite a été mise en évidence par l'étude en MEB dans l'altération de roches granitiques et de micaschistes. Cette transformation débute par le développement d'un réseau losangique à la surface des feuillets de micas. La croissance par épitaxie de tubes d'halloysite est parfois accompagnée par celle de cristaux de goethite. Le MEB montre que l'halloysite se forme directement à partir du mica et qu'elle apparaît dans les tous premiers stades de l'altération, quelles que soient les conditions.

Although it is generally agreed that Fe and Al can act to bind soil particles, their relative efficiencies as aggregants are still disputed. In this work, the aggregating efficiencies of both aged and non-aged Fe and Al oxides precipitated on kaolin or quartz substrates were characterized by comparing their effects on particle size distributions (PSD). To facilitate comparison of PSD data, these were parameterized by fitting them with five different probability density functions (the normal, lognormal, Jaky, fractal and Rosin-Rammler functions). The best fits were given by the Rosin-Rammler function (R2 = 0.997), whose α parameter was used to compare the aggregating efficiency of Fe and Al oxides: in order of decreasing efficiency, non-aged Al > non-aged Fe ≈ aged Fe > aged Al-precipitates.

It is suggested that piperidine may be useful in the identification of clay minerals during differential thermal analysis, particularly in the differentiation of expanding and non-expanding lattice minerals. Differential thermal analysis of two montmorillonites showing similar X-ray powder photographs indicated large differences in the distribution of cation-exchange sites.

Fifty per cent. of the soils studied came from the United States and represent samples from sites in which engineering difficulties were encountered; therefore, it is significant that the clay in 50% of all soils examined was an illite-smectite type, while illite-chlorite comprised 15% of the total. For illite-smectite clays, quantitative estimation of the illite and smectite percentages is obtained from the total potash and glycol retention data. The agreement between measured and calculated cation exchange capacities is taken as supporting evidence of the reliability of the methods used. The chlorite component in the illite-chlorite clays was a high-iron chlorite. Regular and random stratification of illite and chlorite components was observed. The most important influence of composition on behaviour is the very high water sensitivity of the expansive minerals. Most of the soils studied which had caused stability or volume change problems in the field contained expansive minerals. For soils with fines of a single mineral species or a simple mixture of minerals, predictions of behaviour can be made with fair accuracy from a knowledge of soil composition. Where the soil fines are interstratified minerals or cemented crystals, predictions can seldom be made with accuracy. Interstratification or cementation usually inhibits the water sensitivity of normally expansive minerals. This fact seriously limits the value of soil compositional data to the engineer.

By the employment of suitable sampling and analytical methods a marked degree of vertical variability is shown to exist in two exposures of Oxford Clay. Very little of this variation was apparent on visual examination of the strata. Some lateral variation exists between the two exposures, which are thirty miles apart, but this is on a relatively minor scale.

Trends for the vertical variation have been determined and these are in the main common to both areas. The lowest beds are high in organic content and low in acid-soluble lime, whilst higher up in the succession the amount of organic material diminishes and the percentage of lime increases. When examined in greater detail these trends are found to be more complex: they are the resultant of innumerable small scale sedimentary cycles. Thermal methods of analysis have shown that the organic material present in the lowest sixty feet or thereabouts of the Buckinghamshire succession, differs considerably in its ignition range from that found in the next twenty feet. In some respects the characteristics of the higher-level combustible resemble those of lignite. D.t.a. examination suggests that the clay mineral illite is dominant in all layers of the succession in Buckinghamshire. Some montmorillonite may be present in certain of the higher zones either as a simple impurity or in the form of an interlayering with the illite.

The effects of some aspects of these variations on the processes of Fletton brickmaking are discussed.

The majority of investigations of soil electrical characteristics are concerned with tropical and subtropical regions and hence there is little information about soils from other regions. The present study attempts to discover the most important constituents affecting soil electrical charge characteristics in a temperate zone. The study area is located on southern coastal zones of the Caspian Sea in northern Iran (Guilan province). The soil moisture and temperature regimes of the region determined by means of Newhall software were udic and thermic, respectively. Six representative pedons developed on granite, andesite, basalt, phyllite and limestone as their parent rocks are described and their physicochemical, mineralogical and electrical properties studied. The results indicate that the point of zero charge (PZC) values are small in all samples and smaller at the surface than in subsurface horizons. There is a positive correlation between pH0 (PZC) values, organic carbon percentage and crystalline Fe (Fed) content. The points of zero net charge (ZPNC) values are <2.5 in all the pedons studied, which refers to large amounts of negative charge in these soils. The results also show that the differences in negative charge development in a pH range from 2.5 to 6 were largest for horizons rich in organic C and least for those with significant amounts of layer silicate minerals. Therefore, the most important variable charge component in all of the soils studied is organic matter which controls the negative charge at the soil surface. The permanent charge (бp) of the soils studied is also large and negative, which agrees with the amount of clay and the mineralogy of these soils.

A clay from the Mediterranean area classified as natural bleaching earth was comprehensively characterized and the quantitative phase content was determined. Morphology and surface characteristics were determined by environmental scanning electron microscopy (ESEM) and nitrogen adsorption. The BET surface area was >200 m2 g–1 and the average mesopore diameter was >10 nm. Thus the clay is suitable for bioseparation of larger proteins. X-ray diffraction (XRD), X-ray fluorescence (XRF), cation exchange capacity (CEC), layer charge measurement and simultaneous thermal analysis (STA) were used for mineralogical characterization. Determination of the phase content by Rietveld analysis was possible only after Sr2+ saturation, while Rietveld analysis of XRD patterns from Na+-saturated clay resulted in a strong overestimation of the amorphous content and masking of the sepiolite. The clay consists of sepiolite, dioctahedral smectite with high layer charge and low stack height, X-ray amorphous matter (probably mainly SiO2) and accessory feldspars.