The lower Permo-Triassic sediments of the Maláguide Complex contain abundant dickite. Whole rocks were studied by optical microscopy, scanning electron microscopy, and X-ray powder diffraction. The 2–20 µm and < 2 µm size fractions were extracted and analyzed by scanning and transmission electron microscopy, X-ray powder diffraction, infrared spectroscopy, differential thermal analysis, and thermogravimetry.

In the coarse-grained samples, the 2–20 µm size fraction consisted of well-crystallized dickite associated with minor quantities of kaolinite, illite, quartz, and hematite. XRD patterns of the fine-grained samples and the <2 µm fractions showed the existence of well-crystallized minerals in which several reflections of dickite (11l, 02l) were absent and the 132/13$\bar 2$ reflections were shifted. These patterns suggest the presence of an intermediate member between well-crystallized dickite and well-crystallized kaolinite. Only locally high-order reflections are present at 10.5 Å and 18–22 Å. DTA and IR data agree with those from XRD.

The observed compositional and structural variations are a function of the lithology and the particle size of the sample. The sequence kaolinite → kaolinite/dickite → dickite is proposed for the development of these materials during Alpine metamorphism.

The crystal structure of bannisterite, a modulated, mica-like mineral species, of general composition Ca0.5(K,Na)0.5(Mn,Fe,Mg,Zn)10(Si,Al)16O38(OH)8·nH2O, has been solved and refined for specimens from Franklin Furnace, New Jersey (FF), and Broken Hill, Australia (BH). The crystals are mono-clinic in space group A2/a, with (for FF) a = 22.265(1) Å, b = 16.368(1) Å, c = 24.668(2) Å, β = 94.285(5)°; and (for BH) a = 22.286(1) Å, b = 16.386(1) Å, c = 24.575(2) Å, β = 94.355(7)°; Z = 8. Refinement with anisotropic thermal factors reached Rw = 0.034 (FF) and 0.039 (BH). Like stilpnomelane and ganophyllite, bannisterite has a modified 2:1 trioctahedral layer structure in which some of the tetrahedra are inverted towards the interlayer region and linked to inverted tetrahedra in the opposite layer. The octahedral sheet is strongly corrugated along b. The tetrahedral sheet consists of 5-, 6-, and 7-fold rings, and bond distance calculations indicate that Al is concentrated into two of the four inverted tetrahedra. The interlayer Ca, K, and H2O species are highly disordered, as indicated by anomalously large temperature factors and partial occupancies. Localized differences in the Al/Si arrangements in the inverted tetrahedra induce disorder among the interlayer cations.

The transformation of smectite into kaolinite and kaolinite-smectite interstratification were studied in samples belonging to the Argiles Plastiques formation of the Paris basin, by high-resolution transmission electron microscopy (HRTEM). Two original smectite phases, 1) beidellite with 1-nm-thick layers, and 2) beidellite-montmorillonite with 1.25-nm-thick layers, are progressively transformed into kaolinite-smectite mixed-layer minerals, and into kaolinite. As the percentage of kaolinite layers increases in the interlayered minerals, the kaolinite-smectite layer sequences, initially disordered, become locally more ordered, with the presence of KS and KKS units repeated 2 to 4 times (K = kaolinite layer, S = smectite layer). Two solid-state mechanisms seem to be responsible for the formation of kaolinite: 1) the transformation of 1 smectite layer into 1 kaolinite layer, denoted S → K, by stripping of a tetrahedral sheet and the adjacent interlayer region; 2) the intercalation of 1 kaolinite layer into smectite, denoted 0 (zero)→K. Structural and chemical incidences of these mechanisms are discussed.

Sorptive properties of organoclays may be greatly influenced by the physicochemical properties of organic sorbates. Hexadecyltrimethylammonium(HDTMA) clays were prepared using a high-charge smectite (HDTMA-SAz-1), a low-charge smectite (HDTMA-SWy-2), and an illite (HDTMA-ILL). The resultant organoclays were used to sorb aqueous phase 1,2-dichlorobenzene (o-DCB), 1,3-dichlorobenzene (m-DCB), and 1,4-dichlorobenzene (p-DCB). Sorptive characteristics of these compounds were determined by their molecular polarities (o-DCB > m-DCB > p-DCB) and the HDTMA-clay interlayer distance. HDTMA-ILL was used for comparison to HDTMA-SAz-1 and HDTMA-SWy-2. All dichlorobenzene isomers were directly intercalated in the interlayers of HDTMA-SAz-1, causing interlayer expansion. o-DCB and m-DCB were not intercalated in the interlayers of HDTMA-SWy-2 at low concentrations, but intercalation occurred at higher concentrations, which caused interlayer expansion. The concentration needed to produce interlayer expansion depended on the solute molecular polarity, hence a higher concentration of m-DCB than o-DCB was required. p-DCB was sorbed primarily by the HDTMA phase on the external surfaces of HDTMA-SWy-2. In the presence of chlorobenzene (CB), p-DCB sorption by HDTMA-SWy-2 is greatly enhanced, owing to the interlayer expansion by CB and a cosolvent effect. Sorption of o-DCB resulted from both direct solvation-type interactions with HDTMA and partitioning into HDTMA. Such sorption results in double-sigmoid isotherms. m-DCB weakly solvates the HDTMA and partitions into the HDTMA, displaying either a double-sigmoid or a type-III isotherm depending on clay type. p-DCB lacks ability to solvate HDTMA and partitions into HDTMA as its sole mechanism, producing type-III isotherms. HDTMA-clays are potentially effective for treating dichlorobenzene-contaminated wastewater.

Pillared structures with an interlayer opening of ∼0.3 nm were obtained after successive heat treatments of the PILC precursor in reducing and oxidizing conditions. This precursor was prepared by reacting a Na+-montmorillonite with an intercalant containing Al and Fe oxo-hydroxides (Al/Fe = 1). Powder X-ray diffraction, elemental analysis, 57Fe Mössbauer spectroscopy, catalytic activity measurements and surface area data were used to characterize the samples. On the basis of Mössbauer spectra taken at temperatures between 4.2 and 300 K, it is deduced that oxidizing steps produce Al substituted maghemite which converts into Al substituted magnetite upon reducing heat treatment. Firing the precursor in oxidizing atmosphere forms pillars of few nm in diameter. However, heating under reducing conditions yields pillars of smaller diameter. This later behaviour is maintained even after reheating the material in oxidizing atmosphere. From the temperature dependence of Mössbauer spectra it is deduced that the diameter of the Fe oxide particles in the pillars is smaller than 10 nm.

Currently, two commercial plants, operating in the Athabasca region of Alberta, produce approximately 20 percent of Canada's petroleum requirements from oil sands. Surface mined oil sand is treated in a water based separation process that yields large volumes of clay tailings with poor settling and compaction characteristics. Clay particles, suspended in the pond water, interact with salts, dissolved from the oil sands ore, to produce mature fine tailings (MFT) containing only 20 to 50 w/w% solids. As a result, large sedimentation ponds are required to produce enough process water to recycle for the plant. Tailings pond dykes can only be constructed during a short summer season. Consequently, the capability to predict production rate and final volume of MFT is essential for mine planning and tailings disposal operations.

Previous research has demonstrated that a small fraction of nano sized clay particles (20 to 300 nm) effectively controls the bulk properties of MFT. These particles are present in the original ore and become mobilized into the water phase during the oil separation process. In this work, the nano sized particles have been separated from the bulk tailings and subjected to a fundamental study of their flocculation behavior in model tailings water.

Photon correlation spectroscopy and a deuterium NMR method were used to follow particle flocculation and gelation processes. These results were correlated with particle settling data measured under the same conditions. It was determined that the nano particles form fractal flocs that eventually interact to give a thixotropic gel. The ultimate sediment volume produced is almost entirely dependent on the original concentration of nano particles while the rate of water release is governed primarily by electrolyte concentration.

Fifty-two Bidi-Koum bauxites from Guinea, Africa, of diversified chemical composition were characterized for their mineral composition. First, 14 element oxide concentrations were determined by X-ray fluorescence (XRF) using a fusion sample preparation technique. Loss of Mass (LOM) and organic carbon (OC) concentrations were also determined. The initial X-ray diffraction (XRD) phase quantification was carried out employing XDB software. This software allows for full interpretation of a sample diffractogram and helps generate initial concentrations of identified minerals based on a standardless approach. In the stage that followed, the mass balance procedure on the XDB software helped refine the final phase composition. Then, gibbsitic Al2O3 concentrations obtained by wet chemistry for all samples and kaolinitic SiO2 concentrations obtained for selected samples were compared with the concentrations obtained using the XDB software. Phases that were quantified are: gibbsite, boehmite, kaolinite, wavellite, goethite, hematite, quartz, anatase, rutile and illite. Phase concentrations were obtained for illite from K2O and for wavellite from P2O5 concentrations. The alumina substitution in the goethite lattice was also estimated.

The crystal chemistry of Fe-Si scales deposited from geothermal brines at Salton Sea, California, was studied by powder X-ray diffraction and spectroscopic techniques including infrared, 57Fe Mössbauer, 27Al and 29Si nuclear magnetic resonance (NMR), and Fe and Si K-edge extended X-ray absorption fine structure (EXAFS). Scales precipitated at near 250°C from dissolved ferrous iron and silicic acid are composed of hisingerite. This phase is shown to possess the same local structure as nontronite and is a poorly-crystallized precursor of the ferric smectite. A clear distinction can be made at the local scale between hisingerite and 2-line ferrihydrite because, even in their most disordered states, the former possesses a two-dimensional and the latter a three-dimensional anionic framework. At temperature near 100°C Fe-Si scales are a mix of Al-containing opal and hydrous ferrous silicate, whose local structure resembles minnesotaite and greenalite. This hydrous ferrous silicate is very well ordered at the local scale with an average Fe coordination about Fe atoms of 6 ± 1. The difference in crystallinity between the ferrous and ferric silicate scales was related to variations of growth rates of clay particles precipitated from ferrous and ferric salt solutions. The low crystallinity of the ferric smectite suggests that the oxidation of ferrous iron occurs before polymerization with silica.

Smectites synthesized from experiments at 5.5 GPa and 1500°C are of high quality, crystals are large at >10 μm, and the 2:1 layers may have a homogeneous charge distribution. Smectite was exchanged with various cations (Na+, Li+, K+, Ca2+, and Mg2+) and the hydration behavior of each sample was observed by an in situ powder X-ray diffraction method under precisely controlled relative humidity (RH). The smectite showed distinct stepwise (discontinuous) hydration versus RH. During the transition between two hydration states, the coexistence of the two states was observed. Randomly interstratified structures with one and two planes of H2O are time-dependent phenomena and relate to hydration and dehydration processes.

The correlation between illite/smectite (I/S) diagenesis and mean vitrinite reflectance (Ro) data is examined in mudrocks from a hydrocarbon exploration well (geothermal gradient 35°C km−1) from the Great Hungarian Plain of the Pannonian Basin System. The expandability of I/S decreases with depth and there is a change from random to ordered mixed-layering at about 2500 m depth. At this depth Ro is about 0.6%. Comparison of the correlation of expandability and Ro from this study to published data for the Vienna Basin and the Transcarpathian Basin, sub-basins of the Pannonian Basin System, shows that the correlation is systematically different for each sub-basin, according to their thermal histories. In the Vienna Basin (geothermal gradient 25°C km−1), for any given value of Ro, the expandability of I/S is less than in the Transcarpathian Basin (geothermal gradient 55°C km−1) and the sediments are older and more deeply buried. Data from the present study are intermediate. This variation is believed to be due to the effect of time on the smectite-to-illite reaction. Results of an optimization procedure to calculate the kinetics of the smectite-to-illite reaction, using as input the expandability depth profiles, and thermal histories constrained by comparison of observed and calculated Ro data, showed that I/S diagenesis in the Pannonian Basin System can be modelled by a single first order rate equation:

$-dS/dt=e^{log(A)-E/RT}\cdot S$

The highest frequency near-infrared (NIR) combination bands for specimens of four species of mica—montmorillonite-beidellite, illite, chlorite, and kaolinite—were correlated with respect to Al2O3 content. A direct linear correlation was found between the combination band positions and the Al2O3 contents of the montmorillonite-beidellite series, which may be given as: ν̄ cm−1 = (5.38 ± 0.04) (% Al2O3) + (4412.8 ± 0.9). A similar linear correlation for muscovite is: ν̄ cm−1 = (6.10 ± 0.25) (% Al2O3) + (4434.1 ± 8.3).

Possible NIR band interferences are shown for different mineral mixtures, along with the correlation of different illites with muscovite. No combination bands were found in the frequency region 4425 cm−1 to 4625 cm−1 for specimens in which the Al2O3 content was only in the tetrahedral layer sites.

The structure of Li- and Cs-montmorillonites was studied using infrared (IR) reflectance spectroscopy. The spectra of heat-treated clays between 80 and 220 °C were analyzed by Kramers-Krönig inversion in order to obtain the optical and dielectric properties of the clays. The analysis revealed the transverse-optic (TO) and longitudinal-optic (LO) components of the asymmetric stretching vibration of Si-O-Si bridges. Major differences, in particular the systematic development of new bands, were found in the Li-montmorillonite LO and TO spectra with increasing temperature. These changes were attributed to the migration of the Li-cations into the layer structure.

Poorly crystalline authigenic alteration products of basic pyroclastics from the Golan Heights, Israel, were investigated by XRD, DTA, TGA, FTIR and chemical analysis. Modeling XRD patterns with the use of NEWMOD code provided a way to identify these clays as random interstratified illite/smectites (I/S) with ∼70% of illitic interlayers. Their characteristic features were very poor basal reflections, distinct hk bands, high CEC and low (∼2%) K2O content. Crystallite thickness distribution was found to follow Ergun's model with a weight-average thickness of 2.7–2.8 layers. A new method was proposed to calculate the proportion of kaolinite and 2:1 minerals in their mixtures and the average crystallochemical formula of 2:1 minerals in the presence of kaolinite. The method starts from data of chemical analysis and TGA and assumes that the anionic frameworks of kaolinite and 2:1 minerals are exactly O10(OH)8 and O10(OH)2 respectively. The number of OH-groups per ten oxygens not bonded to H in the empirical formula of the mixture is used to evaluate the proportion of kaolinite. Formation of I/S in well-drained environments under humid mediterranean climatic conditions was attributed to long dry seasons. Interstitial water composition was shown to be consistent with authigenic formation of I/S.

Illite crystallinity and fluid inclusion techniques are used to understand the thermal histories of rocks on either side of the disconformity between the Lower and Upper Paleozoic strata in South Korea. Illite crystallinity studies show that the metamorphic grade of the upper strata of the Lower Paleozoic Joseon Supergroup, platform carbonates with subordinate siliciclastics, belongs to the epizone and that of the lowermost strata of the Upper Paleozoic Pyeongan Supergroup, paralic to nonmarine clastics, belongs to the anchizone. The maximum mode of homogenization temperature for fluid inclusion of the uppermost strata of the Joseon Supergroup is 260 to 270 °C and that of the lowermost strata of the Pyeongan Supergroup is 240 to 250 °C. These data reveal a difference in thermal histories of strata below and above the unconformity, suggesting that, in contrast to the previous supposition of a period of non-deposition, at least a 1-km thick section of sediment was removed by erosion during development of the unconformity. Burial and heat flux from a proposed hot spot are suggested as the dominant factors causing differences in a metamorphic grade for the Joseon Supergroup before the deposition of the Upper Paleozoic strata.

Trioctahedral smectite is a constituent of Mg-rich carbonate crusts and moonmilks (pasty deposits) in caves of the Guadalupe Mountains of southeastern New Mexico. Energy dispersive X-ray microanalysis of individual crystallites and their aggregates along with the X-ray diffraction analysis indicates that the smectite is probably stevensite. Saponite is likely present in some samples also. The smectite is intimately associated with dolomite crusts and huntite moonmilks in Carlsbad Cavern, Lechu-guilla Cave, and other dolostone caves. Clay particles appear as fibers and films, with aggregates comprising decimicron-sized filamentous masses that envelop crystals of dolomite, huntite, and magnesite. The occurrence of smectite is related to the genesis of the Mg-rich carbonate minerals. In water films, progressive evaporation and carbon dioxide loss results in the sequential precipitation of Mg-rich calcite, aragonite, dolomite, huntite, and magnesite. This sequence of carbonate precipitation removes Ca and greatly increases the Mg/Ca ratio in the solutions. Silica is commonly available probably because of high pH conditions, and consequently, smectite forms in the Mg-rich alkaline environment. Along with the Mg-rich carbonate minerals, opal, quartz, and uranyl vanadates may precipitate with the smectite.

A series of reduced-charge (RC) hectorites were prepared by multiple heat (250°C) treatments of Mg-saturated hectorites (SHCa-1 ). Cation exchange capacity (CEC) measurements and alkylammonium exchange indicated that a decrease in layer charge occurred with each Mg-250 treatment. Chemical analyses showed that decreases in structural Li and increases in structural Mg contents coincided with charge reduction. Fluorescence measurements of adsorbed quinoline indicated that the hectorite surface was acidified during charge reduction; hydroxyl group deprotonation is a possible source for the acidity. Fourier transform infrared spectra (FTIR) indicated that the Mg-250 treatment induced the loss of structural Li and shifted the SiO stretch band to a position similar to that in talc. The relative intensities of the OH and SiO stretch bands in FTIR spectra suggest that some of the hydroxyl groups in hectorite were lost, possibly by deprotonation. However, thermogravimetric data (TG) reveal no significant difference in the hydroxyl contents of the hectorites.

The FTIR spectra, CEC, layer charge, chemical, and TG data all supported the view that Mg substitution for octahedral Li occurred which resulted in a more “talc-like” structure. Charge reduction in smectites is evidently a general phenomenon and can be induced by heat treatment with the proper exchangeable cation. The ability to reduce the charge of hectorites makes it possible to prepare a series of clays which vary in charge but lack structural Fe. Such RC smectites should be suitable for expandable clay mineral studies which utilize spectroscopic techniques that are sensitive to Fe content.