Garnierite from the Tocantins Complex at Niquelandia, Brazil, is a 15Å, dioctahedral clay mineral, nickeliferous nontronite. The principal octahedral cations are Fe3+, Al and Ni. The ferric state of the iron has been verified by ESCA. Ni occupies both the octahedral site and an exchange site. The garnierite formed (and is still forming) by the weathering of nickeliferous pyroxenite. Although the garnierite is a secondary product of weathering, it undergoes further change as weathering progresses: Ni and silica decrease, Fe3+ and Al increase, and the color changes from bright yellow green to red brown. Eventual breakdown of the garnierite leaves mainly hydrated oxides of iron and aluminum.

The shrinkage of osmotically swollen natural and artificial blisters on vermiculite cleavages by exchange saturation with fixing cations such as Cs+, Rb+, NH4+, and K+ was investigated by replica electron microscopy. Incomplete collapse of either the natural or artificially produced blisters occurred with Cs+, Rb+, and NH4+ saturation, while K+ saturation completely collapsed the artificially produced blisters but not the natural blisters. The reason for incomplete collapse with Cs+, Rb+ and NH4+ was the incomplete replacement (trapping in the flakes) of interlayer hydrated cations such as Na+ shown by electron probe microanalysis. Much less trapping occurred with K+ saturation. Na+ entrapment increased with increasing size and decreasing hydration of cations, i.e. Cs+ >Rb+ >NH4+ >K+.

Semiquantitative determination of Na+, by electron probe microanalysis, in vermiculite flakes near the edge revealed that 1 N CsCl entrapped as much as 45·6 per cent while 1 N KCl entrapped only 7·5 per cent. In general, more Na+ was entrapped by 1 N solutions than by dilute solutions. With 0·01 N KCl solution, the Na+ entrapment was only 4·4 per cent. The amount of Na+ at the center of the macroflakes was less than at the edge, apparently as a result of more CEC at frayed edges and (or) because of incomplete diffusion of Na+ to the center. Shrinkage of artificial blisters by K+ could thus be attributed to its more effective removal of the interlayer hydrated cations, whereas the other fixing cations were less effective. Natural blisters on vermiculite from Libby, Montana were not completely collapsed even by K+, apparently because the layer charge density was too low in the blister areas.

Montmorillonite clay samples were coated with 16 m-equiv/g of clay or iron plus aluminum as hydrous oxides and aged 1 yr, in suspensions of pH 6 or 8. The magnesium exchange capacity (MgEC) decreased linearly with the amount of non-crystalline aluminum hydrous oxide associated with the clay. Eight to 16 m-equiv of iron per g of clay reduced the MgEC by 20 m-equiv/100g at pH 6, but did not affect the MgEC at pH 8. The quantity of non-crystalline aluminum associated with the clay depended on the suspension pH and aging time, and was unaffected by the coprecipitation of 8–16 m-equiv of iron hydrous oxide/g clay. The crystalline form of aluminum hydrous oxide depended on the suspension pH and was shown by X-ray diffraction to be gibbsite at pH 6 and bayerite at pH 8. Gibbsite and bayerite formed rapidly with a rate dependent on the suspension pH when excess non-crystalline aluminum hydrous oxides were present. The quantity of non-crystalline aluminum hydrous oxides remaining after one year in suspensions of iron hydrous oxides and montmorillonite varied from 2·3 m-equiv/g of montmorillonite at pH 8-4·0 m-equiv/g of montmorillonite at pH 6. Differential thermal analysis and MgEC measurements indicated some regular organization of the iron hydrous oxides, however, crystalline iron minerals were not detected by X-ray diffraction.

The decreasing preference of montmorillonite for K+ relative to Na+ as the clay adsorbs increasing amounts of K+ is shown to be the general rule for the exchange of strongly hydrating ions by weakly hydrating ions. Variability in the mass-action selectivity coefficient is interpreted in terms of a composition-dependent surface entropy, which is a function of the chemical properties of the exchanging ion as well as the nature of the adsorption sites. The generally used mass-action form of exchange equation may only be applicable to exchange systems in which both ions have solution-like mobility at the exchanger surface. It is suggested that experimental variables such as ionic strength can greatly influence the degree of fit of data to a given ion-exchange equation.

Integrated intensities of the fundamental modes of vibrations of ammonium in heat-treated, NH4+-exchanged swelling minerals permits (1) a quantitative determination of the amount of tetrahedral substitutions of Si4+ by M3+ in dioctahedral smectites, and (2) an estimate of the degree of interlayer surface heterogeneity in trioctahedral minerals to be made. This is possible because NH4+ cations balancing the negative charge of tetrahedral sites that are not influenced by an excess positive charge of the octahedral layer have a symmetry lower (probably C3v) than the usual tetrahedral Td symmetry of NH4+. In C3v symmetry the ν1 band is infrared active whereas it is only Raman active in Td symmetry. Protons left after deammoniating dioctahedral smectites with tetrahedral substitutions form interlayer silanol groups, the stretching vibration of which give a band that is distinct from that of octahedral OH-stretching modes.

The dispersion of clays is of great importance in determining various soil properties such as hydraulic conductivity. A procedure which involves fixing followed by embedding of clay particles in an epoxy resin is described. This procedure enables the observation of cross sections of clay tactoids under a transmittance electron microscope, and the determination of the number of plates per tactoid. The use of the procedure for the determination of the relation between the exchangeable sodium percentage (ESP) and tactoid size in suspensions of a Na/Ca bentonite system is presented. It was demonstrated that even at ESP 5 significant dispersion already occurs, the average number of plates per tactoid being 6.6 as compared to 16.1 at ESP 0.

Hydroxyl orientation has a major influence on the strength of the ionic interlayer bonding in micas because of the strong repulsion between the hydrogen and the interlayer cation (IC). In order to determine if other factors also influence the magnitude of the interlayer bond energy, the effect due to the varying H-IC distance, as one finds, for example, between a dioctahedral and a trioctahedral mica, must be removed. This can be done by calculating the bond energy as a function of the H-IC distance; a plot of which is a smooth curve with a minimum energy for the minimum H-IC distance. If there are no other factors which substantially contribute to the interlayer bonding energy, such curves for all micas should be superimposed. If, however, the curves are not superimposed but fall into groups with common attributes (stacking sequence, ionic substitutions, etc.) the energy separations between groups of curves indicate the influence of these other factors.

The results of such calculations for four dioctahedral micas (2M1 muscovite, 3T muscovite, and two 1M muscovites) and four trioctahedral micas (2M1 biotite, 1M phlogopite, 2M2 lepidolite and a 1M MgIV mica) indicate that these curves are at higher energy for dioctahedral than for trioctahedral micas and this energy increase is due to the filling of the octahedral sites. The dioctahedral micas are arranged in terms of energy as 1M ≥ 3T ≫ 2M1 while the order for the trioctahedral micas is 1M ≥ 2M1 ≅ 2M2. In addition, the calculated energies suggest that the distribution of the layer charge between the octahedral and tetrahedral sheets affects the strength of the interlayer bond such that the greater the charge on the octahedral sheet, the stronger the interlayer bond.

Rates of exchange of K with Ca for fine (0·2–2 μm) and coarse (54–75 μm) and for thin and thick (37–45 μm) phlogopite particles were determined using a repeated batch technique, which gave a measure of K selectivity.

Potassium selectivity of the fine fraction was higher than that of the coarse one throughout the exchange process in which 93 per cent of the total K was exchanged from the fine fraction and 100 per cent from the coarse one. Potassium selectivity of the thin 37–45 μm particles was higher initially than that of the thick 37–45 μm particles but the difference disappeared subsequently and practically 100 per cent of the total K was exchanged from both the thin and thick particles.

The results are interpreted as tentatively confirming the hypothesis that bending and deformation of elementary layers during K exchange increase with particle thickness, which in turn increase K exchange and decrease K selectivity.

The K exchange curves for the fine and coarse phlogopite fractions suggest that in natural conditions, as in soils, where K is not continuously removed from solution, vermiculization of coarse mica particles may be not only more complete but also more rapid than vermiculization of fine mica particles.

By using a transmission electron microscope equipped with an energy dispersive spectrometer, it was possible to detect the morphological, structural, and chemical characteristics of individual asbestos fibers and clay minerals without any realignment of the equipment. A rapid and convenient procedure for semiquantitative analysis is proposed. Analyses are given for 21 hydrous silicates, asbestos and clay minerals, by both ordinary chemical and energy dispersive methods. The energy dispersive results were comparable to those obtained by chemical analysis. Application of this procedure to asbestos fibers proved this method to be practical and valid for characterization of asbestos in environmental and tissue samples.

The US–Mexico–Canada Agreement (USMCA) introduced a new compliance institution for labor rights in trade agreements: the facility-specific Rapid Response Labor Mechanism (RRM). The RRM was developed to tackle one particular thorn in the side of North American integration – labor rights for Mexican workers – as it had had detrimental, long-term political–economic consequences for the US–Mexico trade relationship. This article reviews the unique political–economic moment in the United States and Mexico that prompted the creation of this tool. It describes how the RRM works and the considerable financial and human resources the US and Mexican governments deployed to operationalize it. The article then reports a number of stylized facts on how governments used the RRM during its first three years, largely in the auto sector. It proposes paths of potentially fruitful political–economic research to aid understanding of the full implications of the RRM and concludes with preliminary lessons as well as a discussion on the potential for policymakers to assess facility-specific mechanisms for labor or other issues, such as the environment, in future economic agreements.

In 2001 Simons [1] discovered a curious binomial identity which can be written as(1)

An attempt has been made to synthesize nitrogenous clay minerals hydrothermally from silica-alumina gels in the presence of amino acids, namely glycine and lysine. The products have been characterized by X-ray powder diffraction, by analyses for C and N contents, and by their infrared spectra.

Amino acid-montmorillonites have been prepared under hydrothermal conditions of 200–250°C and 1000 atm. Above 250°C the amino acids were degraded to ammonium ions, and ammonium-micas were obtained. Syntheses without the addition of amino acids to gels yielded kaolinite.

The role of organic compounds in the formation of clay minerals seems to be of considerable geochemical significance.

The crystallite sizes in the particles from four fractions of a kaolinite-clay were determined from the broadening of the X-ray diffraction lines. Measurements were made of the <002> and <111> planes whose crystallographic directions correspond to the clay plate thickness and diagonal, respectively. The extent of crystal imperfection was determined by comparing the calculated crystallite size with the mean size based on measurements from electron micrographs. The crystal imperfections were found to be more extensive in the plate diagonal, <111>, than in the plate face, <002>, directions. Electron micrographs of hydrofluoric acid-etched samples revealed plate-edge and plate-face imperfections. The latter show a regularity suggesting a mosaic-like texture in the plate surface. Surface imperfections probably have significant influence on the dispersion and flocculation behavior of kaolinite.