This sub-committee consisting of Mr G. Brown (Chairman), Dr M. H. Hey, Dr D. M. C. MacEwan and Dr R. C. Mackenzie was asked to make proposals for the nomenclature of clay minerals and these proposals were presented in part at a C.I.P.E.A. meeting in Paris in July, 1954, where some useful discussion ensued. The outcome of that meeting was a suggestion that the proposals be published more fully. It is important to remember that these are proposals for consideration and not a set of rules. The Clay Minerals Group would welcome comments on these proposals (adverse or otherwise) or the comments may equally well be sent to C.I.P.E.A.

Chemical variations in individual chlorite crystals of diagenetic origin delineated by energy dispersive X-ray spectroscopy (EDS) in a transmission electron microscope (TEM) indicate a temperature dependent chemical zonation in each grain. Silicon decreases and Al increases with higher temperature resulting in a decreasing Si/Al ratio away from the crystal core reflecting the time and rate of the crystal growth. Chlorite particle-size distributions obtained by scanning electron microscopy (SEM) give steady state profiles which suggests that the chlorite growth is controlled by a grain coarsening process related to Ostwald ripening.

Chemical and mineralogical transformations of phyllosilicates are among the most important in diagenetic environments in all types of rocks because they can exert a large control on the processes taking place in such environments and/or provide constraints for the conditions in which phyllosilicate transformation occurred. Dissolution-precipitation and solid-state transformation are usually the two mechanisms proposed for such reactions depending on the crystal-chemical and morphological similarities between parent and neoformed phases together with knowledge of the environmental conditions. These two mechanisms, however, may be at both ends of the spectrum of those operating and many transformations may take place through a mixture of the two mechanisms, generating observable elements that are characteristic of one or the other. In the present literature, the boundaries between the two mechanisms are not clear, mainly because dissolution-precipitation is sometimes defined at nearly atomic scale. It is proposed here that such small-scale processes are considered as a solid-state transformation, and that dissolution-precipitation requires dissolution of entire mineral particles and their dissolved species to pass into the bulk of the solution. Understanding the reaction mechanisms of diagenetic transformations is an important issue because they impinge on geochemical conditions and variables such as cation mobility, rock volume, fabric changes, rock permeability, stable isotope signature and phyllosilicate crystal-chemistry.

I propose that, in the lower range temperatures at which clay mineral transformations take place, energy considerations favour solid-state transformation, or reactions that involve the breaking of a limited number of bonds, over dissolution of entire grains and precipitation of crystals of the new phase. Large morphological changes are frequently invoked as evidence for a dissolution-precipitation mechanism but changes in particle shape and size may be achieved by particle rupture, particle welding or by hybrid processes in which dissolution-precipitation plays a minor role.

Past and recent studies of phyllosilicate transformations show chemical and structural intermediates indicating a large crystal-chemical versatility, greater than is commonly recognized. These intermediates include tetrahedral sheets of different composition within TOT units (termed polar layers), dioctahedral and trioctahedral domains in the same layer, and 2:1 and 1:1 domains also within the same layers. The existence of such intermediate structures suggests that the reaction mechanisms that generated them are within the realm of the solid-state transformation processes.

In many areas of geotechnical engineering it is necessary to have an estimate of the cation exchange capacity (CEC) of a soil in order to allow preliminary design estimates. Standard methods of CEC determination are time-consuming and involve several steps (e.g. displacement of the saturating cation requires several washings with alcohol). Therefore, a rapid method of CEC estimation would be very useful. During preliminary site investigations, the soil engineering parameters can be estimated from the considerable number of correlations available in the literature. In this study, relationships between CEC and various other soil engineering properties have been investigated, resulting in a quick method for estimating CEC.

Simple correlations were developed between CEC and specific surface area (SSA), soil organic matter (OM), clay fraction (CF), activity (A), Atterberg limits (liquid (LL), plastic (PL), and shrinkage (SL)), and modified free swell index (MFSI) of the soils. Strong correlations are observed between the CEC values and those for ethylene glycol monoethyl ether (EGME) uptake and methylene blue (MB) titration. However, no significant correlation was found between CEC and N2_SSA. No unique relationship was seen between CEC and CF (r2 <0.5). No relationship was observed between CEC and OM in this study. The best correlation coefficient between the CEC and Atterberg limits exists between CEC and LL (r2 = 0.61). No significant relationship was seen between CEC and PL or SL. The correlation coefficient between CEC and MFSI was 0.65. Multiple linear regression analyses were developed to investigate the contributions of different soil parameters to CEC. These analyses show that EGME_SSA, in combination with LL, accounted for 91% of the variation in CEC. Correlations between CEC and EGME_SSA, MB_SSA and LL appear to be sufficiently good to enable an indication of CEC to be estimated from these parameters.

A thin (15–20 cm) Fe-rich intraformational conglomerate in the fresh- to brackish-water Early Cretaceous succession of south-east England contains pisoids and pseudo-ooids of a green clay mineral which has been identified as berthierine. The pisoids (up to 0·5 cm in size) are concentrically laminated, have complex structure, and are frequently nucleated around a sandstone fragment. They show evidence of weathering due to a change in their environment after formation. The ooids have well to moderately well developed concentric lamination, are very often multi-nucleated and do not always completely cover the nucleus. They suggest formation as a result of mineral precipitation as opposed to agitation and accretion. The climate and environment during the Wealden were suited to the formation of Fe-rich soils and it is likely that the pisoids and ooids were originally composed of iron oxyhydroxide and kaolinite, having formed in soil in the Weald Basin. They were then eroded and deposited in the base of a large scour structure as part of the conglomerate. On burial, and the attainment of low Eh conditions, berthierine formed by diagenetic transformation of the pre-existing minerals.

Some uses of clay-supported reagents in fine organic synthesis are discussed, in particular the catalysis of the phase-transfer preparation of formaldehyde acetals by quaternary ammonium montmorillonites. The preparation and some applications of clay-supported ferric nitrate, a new reagent which oxidizes alcohols into carbonyl derivatives, couples thiols into disulphides, nitrates phenols, and oxidatively couples pyrrole and benzaldehyde into tetra-phenylporphyrin, are also described

Residual clays that developed on Permian and Carboniferous glass-rich silicic volcanic rocks (pitchstones, ignimbrites) at the Seilitz and Kemmlitz kaolin deposits, Saxony, Eastern Germany, contain locally abundant lath-shaped illite-rich illite-smectite mixed-layer minerals (I-S). Analyses by XRD and TEM-AES reveal a large illite percentage (>∼90%) and R3 ordering in I-S from Seilitz (>∼90%) and smaller illite percentage (∼70%) and R1 ordering in I-S from Kemmlitz. The clays never suffered a deep burial and there is no geological, petrographic or fluid inclusion evidence for aeolian input or hydrothermal origin of I-S at either deposit. The I-S formed exclusively at the expense of volcanic glass and not from K-feldspar. Residual quartz phenocrysts in the clays still preserve primary glassy silicate melt inclusions and lack secondary aqueous fluid inclusion trails. The dD and δ18O values of kaolinite and I-S are suggestive of low formation temperatures (<40ºC). Rb-Sr and K-Ar dating of I-S-bearing clay separates yield Lower Cretaceous ages at Seilitz and indicates the presence of excess or inherited 40Ar in illite-rich I-S. In contrast, Triassic to Jurassic Rb-Sr ages are obtained for I-S from the Kemmlitz kaolin deposit.

An investigation was carried out on the bioavailability of kaolinite and the role it plays in remediating oil-polluted seawater, since kaolinite is known to enable hydrocarbon-degrading bacteria to grow well. Experimental results revealed that significant amounts of Al and Si dissolved from kaolinite were not observed ((P > 0.05) in comparison with a control sample which contained no kaolinite) in the aqueous phase during the ~24 day experimental period. Transmission electron microscope observations and energy-dispersive spectroscope data revealed that some altered kaolinite particles appeared, connected to intact kaolinite and bacterial cells. Bacterial cells were associated and encrusted with intact and/or altered kaolinite clay particles, where mixed (C, O, Na and Si)-precipitates of kaolinite clays were formed on the surface of hydrocarbon-degrading bacterial cells. However, the uptake of Si (from kaolinite) by bacterial cells appeared to be more prevalent than Al, and there were no significant changes in basal spacings of kaolinite due to these altered kaolinite particles. Separate studies showed that hydrocarbon-degrading bacteria have a high resistance to Si. Thus, the present data suggest that Si from kaolinite may facilitate hydrocarbon-degrading bacterial growth as shown in our previous study (Chaerun et al., 2005), and the C-O-Na-Si complexes on the surfaces of bacterial cell walls may be the stimulator for hydrocarbon-degrading bacterial growth in seawater contaminated with oil spill.

The swelling and cation exchange properties of montmorillonite are fundamental in a wide range of applications ranging from nanocomposites to catalytic cracking of hydrocarbons. The swelling results from several factors and, though widely studied, information on the effects of a single factor at a time is lacking. In this study, density functional theory (DFT) calculations were used to obtain atomic-level information on the swelling of montmorillonite. Molecular dynamics (MD) was used to investigate the swelling properties of montmorillonites with different layer charges and interlayer cationic compositions. Molecular dynamics calculations, with CLAYFF force field, consider three layer charges (−1.0, −0.66 and −0.5 e per unit cell) arising from octahedral substitutions and interlayer counterions of Na, K and Ca. The swelling curves obtained showed that smaller layer charge results in greater swelling but the type of the interlayer cation also has an effect. The DFT calculations were also seen to predict larger d values than MD. The formation of 1, 2 and 3 water molecular layers in the interlayer spaces was observed. Finally, the data from MD calculations were used to predict the selfdiffusion coefficients of interlayer water and cations in different montmorillonites and in general the coefficient increased with increasing water content and with decreasing layer charge.

The preparation of green rusts from sulphate solutions and representative Mössbauer spectra are described. As the samples oxidized readily, attention focused on the Mössbauer parameters at liquid nitrogen and helium temperatures. The spectra recorded at 77 K could be fitted satisfactorily with one ferrous iron quadrupole doublet with a separation of 2·93 mms−1 and one ferric iron quadrupole doublet with a separation of 0·45 mms−1. In some spectra a ferric iron magnetic hyperfine of strength 49·2 T was also apparent. At 4·2 K, the ferrous iron exhibited a hyperfine splitting with a field of 12·4 T whilst the ferric iron exhibited a hyperfine splitting with a field of strength 50·4 T. The ratio of ferrous to ferric ions was 2·25 ± 0·25 at 77 K and at 4·2 K, and ∼1·6 with a large variation at room temperature. The liquid helium spectra did not always give a good chi-squared fit, the main reason being attributed to relaxation. The line-width of the ferrous iron site at 77 K is slightly larger than that for iron metal and could be explained by a variation in the number of near Fe3+ neighbours at different Fe2+ sites, consistent with the assumption that the ferrous iron site is in the hydroxide sheet. The effect of different numbers of Fe2+ and Fe3+ neighbours probably contributed to the increase in line-widths at 4·2 K compared with those at 77 K. The ferrous iron doublet is marginally different to those of chloride and hydroxy-carbonate green rusts and the aluminium analogues.

The removal of gaseous mercury from flue gases from coal-fired power plants is currently an environmental challenge under investigation. Therefore, the main aim of this paper was to evaluate the suitability of faujasite group zeolites (Na-X) to adsorb mercury compounds. Previous, initial tests showed negligible Hg0 uptake by Na-X zeolite, but silver impregnation improved adsorption markedly. Therefore, the testing of mercury adsorption from flue gases into Ag+- impregnated Na-X synthetic zeolite (Ag-X zeolite) derived from coal fly ash was carried out. This material was characterized by X-ray diffraction, scanning electron microscopy and energy dispersive spectroscopy, X-ray fluorescence and nitrogen adsorption/desorption before being evaluated for mercury removal from exhaust gas. After preliminary mercury adsorption tests (fixed bed) under a nitrogen atmosphere, the adsorbent was examined with a simulated flue gas composition under various conditions, i.e. weight of zeolite, temperature of experiment and zeolite in powder and granulated forms. The removal of mercury was shown to depend on the sorbent texture (powder or granulate), exhaust gas flow rate and contact time, as well as the temperature of the experiment. The Ag-X zeolite tested reduced the level of mercury in the flue gas and, depending on the experimental conditions, long-time mercury breakthrough ranges from 15 to 40% were obtained. The best results for mercury capture were obtained for granulated material.

The use of disodium peroxodisulphate combined with a neutral buffer is a new method for the efficient removal of organic matter from clay-bearing sediments. The effects of this oxidation procedure on mineral structure were investigated by treatment of different standard clay minerals (kaolinite ‘china clay’, illite ‘Le Puy’, montmorillonite SWy-1). The materials were characterized by means of XRD, FTIR, SEM and TEM before and after leaching with disodium peroxodisulphate. Systematic experiments were conducted to determine the effects of leaching on the chemical and isotopic composition of oxygen, hydrogen and K-Ar in these samples. Effects on the physicochemical properties of the clays such as BET external surface area, cation exchange capacity (CEC) and expandability with ethylene glycol were also investigated. The results show that structure, chemical composition, oxygen and hydrogen isotope ratios, as well as the K-Ar system remain unaffected by leaching with disodium peroxodisulphate. The CEC and expandability remain unchanged, whereas changes in BET area can be attributed to mechanical dispersion by ultrasonic treatment.

The Japanese archipelago, in the temperate zone, has been affected by volcanic and hot spring action in many geological periods including the Recent one. Complicated clay mineral assemblages have been formed by alteration of volcanic glass both by weathering and hydrothermally, and have been studied by the writer and his collaborators (Sudo, 1950b, 1951; Sudo, Minato and Nagasawa, 1951; Sudo and Ossaka, 1952). The present account, based on these studies and on more recent data, deals with acidic to intermediate types of volcanic glass, which are widely distributed in rocks and soils throughout the islands.

Optical isomers deamination of L- and D-glutamic and aspartic amino acids and of their DL racemic mixtures has been achieved in the presence of Na-montmorillonite at pH = 6 and room temperature. The adsorption curves showed that the enantiomer adsorbed depends on the type of amino acid. Nevertheless, deamination reaction kinetics brought about a stereoselectivity of the clay mineral for the L-isomer and implicitly showed an unquestionable “structural chirality character” of the clay mineral.

Synthetic ferrihydrites with Si added at mass ratios of Si/Fe = 0, 10, 20, 40, 80, and 160 × 10−3 have been studied to examine the effect of Si on the properties of ferrihydrite. The Si proportionally reduces the point of zero charge but influences surface area, loss of weight to 800°C and solubility in acid oxalate solution to varying degrees. At a critical concentration of Si (when Si/Fe = 20 × 10−3) these measured properties indicate a greater particle size and a more ordered structure. The relationship between synthetic ferrihydrite and the surface of kaolinite has been studied by a combination of surface area and charge determinations and TEM. An attraction predicted at pH 3 between ferrihydrite particles and the basal surface of kaolinite has been confirmed, and resulted in a stable coating. However, at pH 6 any attraction between the minerals appears to be too weak to produce a coating of the kaolinite surfaces.

Lateritic weathering profiles developed on serpentinized peridotites of Murrin Murrin (Western Australia) exhibit thick smectite zones (10–15 m). The smectites from plasma and fissures were characterized by XRD, chemical analyses (ICP-AES, SEM-EDX and TEM-EDX) and Mo¨ssbauer spectroscopy. These Fe-rich smectites, previously described as nontronites, are in fact more complex. Their layer charges originate from both the tetrahedral and octahedral sheets. Plasma and notably fissure smectites exhibit, from the bulk sample scale to the particle scale, large and continuous Al for (Fe+Cr) substitutions, covering a chemical gap previously described for dioctahedral smectites ranging between nontronite and beidellite end-members. Lastly, they exhibit an octahedral occupancy slightly above 2, due to a low (Mg+Ni) trioctahedral contribution. Thus, the smectites occurring in weathering profiles of ultrabasic rocks can have actual chemistries intermediate between four dioctahedral end-members (beidellite, nontronite, montmorillonite and previously rarely described ferric-montmorillonite) and a trioctahedral one ((Mg+Ni)-saponite).

The clay fraction from the B horizon of a Psammentic Hapludalf containing vermiculite and smectite was treated with n-alkylammonium chloride ranging from nc = 6 to nc = 16. X-ray data were obtained by step-scanning, stored in a computer, corrected with the Lorentz and polarization factors and then fitted with a deconvolution programme. The layer charge was determined from the uncorrected, the corrected and the fitted diagrams, respectively. The evaluated confidence limits of ξ decreased in the same order revealing the vermiculite to be a high-charge type. The computed charge distribution of the smectite changed from an unlikely bimodal to a nearly symmetrical distribution.

The alkali leaching of two aluminosilicates, kaolinite and metakaolinite, with aqueous NaOH has been studied. Both silicates gave hydroxysodalite (HS) with or without the evanescent zeolite NaA. X-ray diffraction and high-resolution 29Si and 27Al MAS-NMR spectroscopy provide information about the reaction sequence of the clay. The conversion starts with the formation of an amorphous gel precursor at a rate which depends on the alkali concentration but not on the choice of kaolinite or metakaolinite as starting material. The rate of zeolitization of this gel is much faster when it is obtained from kaolinite, probably because it is more homogeneous.

A series of smectites was investigated to reveal the thickness distribution of crystallites. The Fourier decomposition technique of Bertaut-Warren-Averbach (MudMaster program) was applied to XRD reflections of <0.2 μm, glycolated Na-clays. It was shown that the thickness distribution is lognormal and the mean thickness ranges from 5.7 to 12.3 nm (3.4 – 7.3 layers). At higher humidities, characteristic of TEM sample preparation, the mean thicknesses decrease, but the differences in mean thickness between samples are preserved. Beidellites have the thickest crystallites. The relationships between the mean thickness, volume-weighted mean thickness and the parameters of the lognormal distribution were established. Calculation of these parameters is possible, using the area and the maximum intensity of the 001 reflection. The influence of the fluctuations of d-spacing on the peak width was shown. Smectite crystallites, dispersed into individual layers during infinite osmotic swelling and rebuilt through coagulation, recover their original mean thickness and thickness distribution.