Pillared montmorillonite was used as an adsorbent for binary mixtures of hydrocarbons and alcohols (benzene/n-heptane; ethanol/cyclohexane; ethanol/toluene; propanol/ toluene). The adsorbent was prepared from the Na-form of a bentonite from Milos by reaction with polyhydroxoaluminium solutions. The adsorption behaviour of the pillared montmorillonite was characterized by the adsorption excess isotherms and the heats of immersion. Sorption capacities and wetting properties differed significantly from those of the Na-montmorillonite. Benzene was adsorbed preferentially from mixtures with n-heptane. Ethanol and propanol were also preferentially adsorbed from mixtures with cyclohexane and toluene but the curves showed azeotropic points at molar fractions of alcohols of 0.7-0.9. The calorimetric data revealed the partially hydrophobic character of the pillared montmorillonite. The heat of wetting of benzene or toluene on the pillared samples was distinctly higher than that of ethanol whereas ethanol gave the highest wetting enthalpies on Na-montmorillonite.

The ability to produce humic-like polymeric compounds, with L-tyrosine as the starting material, was evaluated using different mineral systems, e.g. on Ca-, A1- and Cu(II)-saturated montmorillonite, nontronite and kaolinite, and on quartz. Clay minerals proved to be effective in the formation of these compounds, but not quartz, except in the presence of Cu(II). The newly formed compounds were fractionated by alkaline extraction. With clay systems, the amounts of substances produced appear to be related more to the interlayer cation than to the clay type. Copper cations appear to be more effective when not associated with the clay structure.

For mixed-layer clay fractions from the North Sea and Denmark, X-ray diffractograms have been recorded for specimens saturated with Mg, Ca, Na and NH4, both airdry and intercalated with ethylene glycol, and the patterns have been computer-simulated with a multicomponent program. The mixed-layer fractions consist of an illite-smectite-vermiculite (I-S-V) phase constituting ~90% of the fraction and a kaolinite-illite-vermiculite (K-I-V) phase. For each I-S-V, the degree of swelling in swelling interlayers depends on both interlayer cation and glycolation, whereas the amount of non-swelling illite and swelling interlayers and the interstratification parameters are constant. Based on structural characteristics and the degree of diagenetic transformation, the samples investigated can be divided into three groups. The I-S-V of group one is predominantly detrital and has 0.69-0.73 illite, 0.26-0.20 smectite and 0.04-0.07 vermiculite interlayers, the illite, smectite and vermiculite interlayers being segregated. The I-S-V of group two has been diagenetically transformed and has 0.80 illite, 0.12 smectite and 0.08 vermiculite interlayers, the vermiculite interlayers being segregated whereas the illite and smectite have the maximum ordering possible for R = 1. The I-S-V of group three has been further transformed during diagenesis and has 0.84 illite, 0.08 smectite and 0.08 vermiculite interlayers. Statistical calculations demonstrate that the I-S-V transformation can be described as a single interlayer transformation (SIT) within the crystallites.

The distribution, mineralogy, petrology and bulk and stable isotope chemistry of altered volcanic ash beds in the marine sediments of Mid-Triassic age (Etalian) at Kaka Point, New Zealand, are described and related to lithofacies and the geological processes controlling their development.

Three varieties of altered ash occur in the Kaka Point sediments — porcellanite, claystone (bentonite) and albite-rich. Porcellanites are quartz-rich and may contain analcime and heulandite: they are restricted mainly to the on-shore facies. Claystones are rich in smectitic clay minerals and occur in both the on-shore and off-shore facies. They often contain diagenetic nodules of analcime, quartz, apatite and carbonates. The authigenic carbonates of the on-shore facies are variable in composition (sideritic, rhodochrositic, calcitic), whereas in the off-shore facies they consist only of calcite. The albite-rich lithology is very rare and is known only from the off-shore facies.

The development of the porcellanite and albite-rich lithologies was restricted to slowly deposited, relatively coarse-grained ash sediments in which extensive interchange took place between the sediment's pore-waters and ambient seawater, resulting in enhanced microbial activity and high pH throughout the pore-waters of the suboxic zone beneath the water-sediment interface. The high pH increased the rate of volcanic ash hydrolysis and provided the conditions necessary for the precipitation of zeolite, feldspar and quartz. The development of smectitic claystones was associated with more rapid deposition and limited interchange between the pore-waters of the parent ash and ambient seawater. The pore-water alkalinity was generally lower and enhanced microbial activity and high pHs were restricted to patches of sediment at which quartz, analcime, apatite and carbonates formed diagenetic nodules. Modelling of the stable isotopes of the smectitic clays (δ18O, δD) and diagenetic carbonates (δ18O, δ13C) suggest that: (1) ash argillization in the on-shore facies took place in brackish water (∼25% meteoric water) at an average temperature of ∼50°C and in the off-shore facies in marine pore-waters (∼10% meteoric waters) at ∼40°C and (2) diagenetic carbonate precipitation in the near-shore facies took place at ∼30°C and in the off-shore facies at 60–80°C.

The pattern of ash alteration in the marine Triassic sediments at Kaka Point is considered to represent an early stage in the development of the zeolite pattern associated with the classic area of zeolite facies metamorphism in the Taringatura and Hokonui Hills.

In samples of slate from the Fomeque Formation near Bogota, Colombia, pyrophyllite was found to occur together with mixed-layered illite-smectite, chlorite and illite. Other minerals were quartz, K-feldspar, dolomite and pyrite. X-ray diffraction patterns revealed that the mixed-layer represents an R1 ordered rectorite with 80–90% illite layers. The microfabric is developed as a closely spaced cleavage in the phyllosilicate-rich rocks, and grades into a fracture cleavage with coarsening of the grain size. No cleavage was observed in the interbedded siltstones. It is suggested that the microfrabrics developed in these rocks correspond to high diagenetic to anchizonal conditions. The illite crystallinity from the slate has been measured on glycolated samples and ranges from 0.47 to 0.55°Δ2θ with a mean of 0.52°Δ2θ Based on the stability of R1 ordered rectorite, the illite crystallinity and the microfabric development, it is proposed that the rocks have been subjected to a temperature of ∼200°C at low pressure. At this temperature, pyrophyllite can only be stabilized at the expense of kaolinite and quartz if aH2O ≪ 1.

Palaeoweathering profiles are widely represented in the Iberian meseta. Transmission electron microscopy (TEM) and analytical electron microscopy (AEM) were used to describe the mechanisms governing the processes involved in the formation of one of these weathering profiles developed over slates of the Iberian Hercynian Massif. Three well-differentiated weathering stages were distinguished, based upon well-defined mineralogical signatures characteristic of primary or secondary minerals. The lower stage is characterized by fresh green slates composed of Fe-chlorite, micas, quartz and feldspars. The soft slates represent an intermediate weathering stage. A confined environment has permitted the development of smectite from the different primary phyllosilicates, both by neoformation of montmorillonite and transformation into beidellite. In the upper part of the profile, the red slates are the most weathered. A tropical or subtropical climate has resulted in the formation of kaolinite and abundant iron oxides over several metres. The present study demonstrates that the three identified weathering stages were formed under the same climatic conditions. Such ‘toposequences’ are developed at the present time in tropical areas (Bocquier, 1971).

The nature and composition of the Fe minerals in the rusty ferruginous material frequently located in the zone of contact between the thallus of Stereocaulon vesuvianum and the leucite bearing rock of Mt. Vesuvius have been studied by microscopic and submicroscopic investigations (SEM, TEM with EDXRA) complemented by X-ray diffraction and chemical analysis. Ferrihydrite is likely to be the main component of the short-range order iron oxyhydroxide pool, although the possibility that significant feroxyhite may be present cannot be completely excluded. Hematite and goethite are the crystalline iron oxides. The organic acids produced by lichens play a key role in the enrichment of poorly-ordered phases at the rock-lichen interface. It is suggested that the peculiar morphology of the Stereocaulon vesuvianum thallus and the irregularity of the volcanic rock surface lead to different microsites in the rock-lichen interfaces which have their own conditions of pH, humidity and redox potential, favourable for the neoformation of crystalline phases.

An homogenous 8.4 Å hydrate was obtained after washing intercalated KAc- nacrite. X-ray diffraction analysis based on comparison of the experimental and calculated profiles enabled the amount of water (one molecule per Si2Al2O5(OH)4) and the z coordinate along c* (6.5 Å) to be determined. The hydration state was accompanied by a decrease in the coherent domain along c* in the order nacrite > KAc-nacrite > H2O-nacrite. The IR spectrum of the hydrated nacrite showed an evolution of the structure with a shift of ν(OH) from 3702, 3649 and 3630 cm−1 to 3690, 3641 and 3620 cm−1, respectively for the nacrite hydroxyls. The ν(OH) stretching bands of the interlayer water appeared at 3602 and 3545 cm−1 and their bending band at 1655 cm−1. The TGA/DTG analysis of the air-dry hydrated nacrite showed a loss of water at 245°C the weight loss (1 molecule per Si2Al2O5(OH)4) corresponding to the interlamellar water, in agreement with that determined by XRD.

Raman microscopy of the kaolinite polymorphs was used to study single crystals and bundles of aligned crystals of kaolinite. The spectra of the hydroxyl stretching region were both sample and orientation dependent. Kaolinites can be classified into two groups according to the ratio of the intensities of the 3685 and 3695 cm−1 bands. No relationship was found between the d-spacing and the crystal domain size measurement from the 001 reflection and the Raman spectral intensities indicating the Raman spectra are independent of d-spacing and crystallinity. However, a relationship of the crystallinity in the a-b direction and intensities of the 3685 and 3695 cm−1 bands indicate that the relative position of one layer to the other determines the position of the inner surface hydroxyl groups and the hydrogen bonding with the oxygen of the opposite layer. A new hypothesis based on symmetric and non-symmetric hydrogen bonding of the inner surface hydroxyl groups is proposed to explain the two inner surface hydroxyl bands centred at 3685 and 3695 cm−1. The bands at 3670 and 3650 cm−1 are described in terms of the out-of-phase vibrations of the in-phase vibrations at 3695 and 3685 cm−1.

The ease with which sorbed Cr(III) is released to solution via oxidation or cation exchange depends on its mode of complexation and the broader chemical environment in which it is held. This study was conducted to elucidate the chemical environment of hydrolysed Cr(III) sorbed onto montmorillonite, both alone and coprecipitated with Al. The 27Al MAS NMR revealed that Cr in the coprecipitated hydroxy interlayer created a second environment for AI, slightly more shielded than that of Al in the montmorillonite 2:1 layer. This observation is evidence for the presence of numerous Al-O-Cr linkages, thus revealing a uniform distribution of Al and Cr within the hydroxy polymers. The 29Si MAS NMR revealed a second environment for Si in the tetrahedral sheet of the Cr clays. This environment could be created only through a redistribution of electrons at the siloxane surface caused by inner-sphere complexation of Cr(III). Due to this inner-sphere complexation, sorbed Cr(III) is difficult to displace via simple exchange reactions and, consequently, its bioavailability is decreased.