Varty & White's application of multivariate analysis to Grim & Kulbicki's measurements on montmorillonites has been re-examined and extended. Inconsistencies between their table of scored data and derived similarity table, and some unexplained errors in the similarity table, have only a small effect on their results. Similarities calculated from Grim & Kulbicki's data, using a different similarity coefficient, lead to a two dimensional representation which separates the groups of montmorillonites more clearly. The groups can be clearly separated even in a one dimensional representation, by changing the relationship between distance and similarity.

Kaolinite cation adsorption data are processed using recent gas adsorption concepts such as the undersaturation ∆m = ln (C/Cs) and the monolayer coverage y. This process shows that using the proper reference phase through its solubility Cs, it is possible to characterize adsorption sites that have the same adsorption energy regardless of the nature of the cation. Under mildly acidic conditions, a single ‘Langmuirian’ site category fits cation adsorption data whereas another family of sites is revealed in mildly alkaline conditions. These results suggest that at mildly acidic pH, only silanol sites are available to ion exchange and adsorption whereas at higher pH, a wider range of sites is made available, some of them displaying the same average adsorption energy and the others constituting a different category of sites with a much lower adsorption energy. This latter category is attributed to the aluminol sites.

Separation of the clay fraction from a calcareous soil usually involves chemical pretreatments which could affect the separated clays. A technique based on separating the flocculated particles (flocs) of a sonified soil-water suspension was used on highly calcareous samples and a highly gypseous one collected from a limestone ridge in Egypt. The relative abundance of the clay minerals in flocs (identified by XRD and electron microscopy) was found to be identical to that of < 1 μm clay separated by sedimentation. The suspensions were prepared by washing the soils repeatedly with distilled water (about 2 1/g) until spontaneous peptization.

Washing removed both 'amorphous' silica and alumina as detected in the flocs. The composition of poorly-ordered aluminosilicates (SiO2/Al2O3) of the 1μm clays was heterogeneous whereas in the flocs it was homogeneous.

Fluoride reactivity of both clay separates and prepared mixtures of CaCO3 with palygorskite (the dominant clay mineral present) was also studied.

Extensive deposits of red glacial drift and lacustrine clay occur along the east coast of Aberdeenshire and constitute the parent materials of important agricultural soils. The mineralogy of lacustrine clay at Tipperty, Aberdeenshire, has been determined by X-ray, differential thermal, and optical methods. General relationships between the mineralogy of this soil parent material and that of other red drifts in the vicinity are discussed with reference to the glaciology of the region. It is suggested that these red drifts were transported from the bed of the North Sea and not from Strathmore.

Room-temperature dehydration of aqueous coal slurries, coal extraction residue, or coal ash results in spontaneous luminescence. The phenomenon is characterized by a monotonic decay in photon activity which precedes a sharp rise in photon release. A maximum is reached within several minutes but subsequent decay is slower and photon emission continues for an extended period of time. The magnitude of photon activity is severely limited by the thickness of the strongly absorbing coal slurry. Prior removal of mineral matter from the coal appears to curtail the dehydration-induced phenomena, suggesting that clays or clay-organic interactions are responsible. Data also suggest that air is required as a medium for discharging the excited species.

The mineralogy of the fine clay fraction (<0·2 μm) of two soil pedons (Aquic and Udic Haplustalfs) representing the wheat-sugarcane belt of the Indo-Gangetic alluvial plain was studied by X-ray diffraction, differential thermal analysis, transmission electron microscopy, and by chemical analysis. The XRD patterns are characterized by unusually high spacings which are interpreted in terms of an interstratification comprising smectite, illite and ‘chlorite’ components. The CEC data (Ca/Mg and K/NH4) also indicate the possible presence of vermiculite. A plateau bridging the 7–10 Å maxima in K-saturated specimens heated at 300°C suggests interstratification of kaolinite and smectite, although this may not be part of the above interstratification. The diffuse bands shown by Mg-glycerol-solvated Ap-horizon clays at ∼21 Å, and the increasing elimination of XRD peaks in the > 10 Å region with distance from the surface, suggests that the expanding layers have a slight tendency to segregate in Ap horizon samples and that randomization tends to increase with depth. Discrete illite and small amounts of kaolinite were also detected.

It has frequently been suggested that there is more than one structural type of montmorillonite, and the investigations of Grim and Kulbicki have supported this concept. From the data given by these authors, thirty-six characteristics have been selected and the montmorillonites compared using a multivariate analysis computer programme. The results do not support the hypothesis of two types of montmorillonite, but indicate a random distribution of the samples in an n-dimensional space.

Distribution of Fe in the fine fractions of four Czech bentonites was investigated by M6ssbauer spectroscopy. The spectra at room and liquid nitrogen temperatures revealed that most Fe present in the samples is structurally bound in smectite. Microcrystalline and/or Al-substituted goethite was identified in all fine fractions, comprising 8 to 50% of total Fe. This mineral was partly magnetically ordered in the Rokle sample even at room temperature. Two per cent of total Fe was bound in hematite in the Krásný Dvoreček sample. Only octahedral Fe(III) was found in the Rokle and Stebno samples, while Krásný Dvoreček and Hroznětín contained 9 and 38%, respectively, of the total Fe as octahedral Fe(II) and 14% of total Fe was found as tetrahedral Fe(III) in Krásný Dvoreček.

Two zeolitized tuffs (ZTs), viz. a Neapolitan yellow tuff (NYT) and a clinoptilolite-bearing tuff (ZCL), were tested as pedotechnical materials to improve soil resilience against the impact of treatment by a ‘dirty’ municipal sewage system (DSW). Soils (surface horizon) were a sandy, alkaline Entisol (Typic Xeropsamment), and a sandy-loam, sub-acidic Alfisol (Ultic Palexeralf). Results showed that the presence of ZTs resulted in several favourable effects. Electrical conductivity (EC) decreased and pH was buffered. Ammonium was selectively taken up from the DSW, making the zeolitized tuffs almost saturated by NH4+, by exchanging both beneficial cations, such as K+ and Ca2+, thus improving their potential availability to plants, and undesirable cations such as Na+, thereby hindering the exchangeable sodium percentage (ESP) increase and concurrent soil salinization-alkalinization. At the same time, NH4+ was stored as a potentially slow-release nitrogen fertilizer. The mobility of Pb, Cu and Zn dropped off to a large extent. NYT produced the best effects, and the Entisol gained the greatest benefit from treatments.

Chamosite has been identified as a regular member of the suite of minerals constituting the Lower Ecca shales in Natal. In this deposit, chalybite, Fe-chlorite and illite are all found to be secondary to the chamosite component which serves as the principal mineral host for iron, even in beds containing as little as 2·25% Fe. Aspects of composition, fissility and origin are discussed.

The Landshut bentonites that formed from Ca- and Mg-poor rhyolitic tuffs in a fluviatile-lacustrine depositional environment of the Miocene Upper Freshwater Molasse, southern Germany, contain abundant palustrine, pedogenic and groundwater carbonates. Geochemical analyses of dolomites, calcites and smectites from bentonites of various environments by X-ray diffraction, thermal ionization mass spectrometry, inductively coupled plasma-mass spectrometry, and handheld X-ray fluorescence yield new insights into the compositions of fluids and sources of imported components involved in carbonate formation and bentonitization, as well as the timing of bentonite formation. Evaporated, Sr-rich brackish surface water with a molar Mg/Ca ratio of 2–5, derived mostly from the weathering of detrital carbonates, was involved in dolomite and bentonite formation in palustrine and some pedogenic environments. However, Sr-poor groundwater with a molar Mg/Ca ratio of ∼ 1 and a stronger silicate weathering component caused bentonite and calcite formation in strictly pedogenic and groundwater settings. The 87Sr/86Sr and molar Mg/Ca in the smectite interlayers indicate later cation exchange with water having more radiogenic Sr sources and smaller molar Mg/Ca ratios. The Rb-Sr data indicate the common presence of detrital illitic phases in the <0.2 μm fractions of the bentonites. Cogenetic palustrine dolomite and a single smectite residue sample which lacks this detrital illitic phase provide an age constraint for bentonitization at 14.7 ± 4.1 Ma identical to primary ash deposition. Thus a rapid onset of bentonitization of accumulated ash and dolomite formation in evaporation-driven wetland environments is indicated for the genesis of the Landshut bentonites.

Using the adiabatic calorimeter which has been developed by Nagasaki & Takagi (1948) and manufactured by the Rigaku Denki Company, the energy changes associated with the dehydration and dehydroxylation processes of clay minerals were measured at room pressure. The samples studied were mont-morillonite, chlorite (trioctahedral type), and three kinds of interstratified minerals with component layers such as mica, dioctahedral chlorite, and montmorillonite. ΔH-values due to the dehydration of the interlayer region were 9·8 kcal/H2O mole for montmorillonite and 12·4–13·4 kcal/H2O mole for interstratified minerals mica-montmoriIlonite and dioctahedral chlorite-montmorillonite. The values due to dehydroxylation of the silicate layer were 17·7 kcal/H2O mole for montmorillonite, 16·8–17·5 kcal/H2O mole for the interstratified mica- montmorillonite, and 19·3 kcal/H2O mole for chlorite. The value for the dehydroxylation of the hydroxyl layer of chlorite was 19·3 kcal/H2O mole. For the sake of comparison, the heat of transition α↔β of quartz was found to be 140 cal/mole. The reproducibility of these values was in the range of ±5%.

Many safety functions required of the compacted bentonite buffer in the KBS-3 concept rely on processes influenced by the composition of the pore water. Important safety-relevant processes are related to the bentonite buffer, e.g. swelling, precipitation and dissolution reactions, and transport of water, colloids and ions. One of the methods used in analysing pore water in compacted bentonite is the ‘squeezing technique’. Various possible artefacts which can occur during squeezing, such as mixing of different pore-water types, dissolution of accessory minerals and cation exchange, need special attention.

The present work describes the methodology for studying the composition of the non-interlamellar pore water by combining squeezing methods, chemical analyses, microstructure measurements and geochemical modelling. Four different maximum pressures were used to squeeze the compacted bentonite pore water. The origin of the pore water was studied by analysing the bentonite microstructure both before and after squeezing using SAXS and NMR, the cation exchange and dissolution reactions were studied by chemical analyses and geochemical modelling.

The pore-water yield increased from 32 to 48 wt.% from the initial amount of porewater in the samples when the maximum squeezing pressure was increased from 60 MPa to 120 MPa. About 35 wt.% of the water collected originated from the interlamellar (IL) pores. The ratio between IL and non-IL pore waters as well as the composition of the squeezed porewater was constant in the squeezing-pressure range used. The results of microstructural measurements by SAXS were in perfect agreement with previous studies (e.g. Muurinen & Carlsson, 2013). The dissolving accessory minerals have an effect on the ratio of the cations in the squeezed solution while the migration of anions in bentonite seems to be diffusion limited. According to geochemical modelling the chloride concentration of the non-IL pore water in compacted bentonite before squeezing was 0.34 Mgreater than in the squeezed pore water due to the mixing of two main water types.

Alteration of cement–bentonite interfaces and accompanying changes in diffusivity of tritiated water (HTO) was investigated experimentally using intact, hardened cement-paste specimens. The alteration by carbonate solution was accompanied by mineralogical changes at the interface and a decrease in the HTO diffusivity to ∼70 ± 7%of the initial value after a 180-day period. Another alteration in contact with compacted bentonite was accompanied by mineralogical changes at the interface and a decrease in the HTO diffusivity to ∼71 ± 10% of the initial value after a 600-day period. The changes in the diffusivity were considerably less than those observed for mixed specimens of ground, granulated hardened cement paste and bentonite where the diffusivity decreased to 20% of the initial value over 180 days. The results were extrapolated to 15 y under simple assumptions and showed good agreement with those observed in the cement–argillite interface at Tournemire URL (France). Such an explanation enhances confidence in the assessment of the alteration of cement-bentonite systems and might be a basis for using the data and models obtained in the long-term assessment of radioactive waste disposal.

Electron microscopy was used to study swollen samples of n-butylammonium vermiculite prepared in dilute aqueous solutions of n-butylammonium chloride. Three electrolyte concentrations were studied, 0.1 M, 0.01 M and 0.001 M. The 0.1 M samples studied were in a taetoid phase, exhibiting crystalline legions of about ten layers separated by large irregular aqueous regions. The dilute samples were studied in their gel phase, exhibiting regular spacings of 85 nm and 55 nm in the 0.001 M and 0.01 M solutions, respectively. These spacings are much larger than those measured previously by neutron scattering, probably due to an additional expansion of the interlayers during the freezing process employed in preparing the replicas. In all examples, the structures were found to be lamellar over regions of several microns.

The photo-oxidation of tryptophan (TRP), photosensitized by methylene blue (MB) exchanged on hectorite, Wyoming bentonite and laponite is strongly influenced by three factors: (i) Fe(III) in the structure, which quenches the excited state of MB; (ii) the adsorption site of MB, as photo-oxidation only takes place with MB on the external surface; (iii) dye aggregation, which reduces the yield. Rose bengal (RB), chemically anchored on the external surface of Barasym does not sensitize the photo-oxidation of TRP.

Early Copper Age pottery sherds discovered in a cave within the crystalline dolomites of the Southern Carpathians (Romania) were investigated by polarized light optical microscopy (OM), X-ray powder diffraction (XRPD) and electron microprobe analysis (EMPA) to obtain information on the pottery production in the Copper Age in the territory of present-day Romania. Microscopically, the clayey matrix of the ceramic body is highly birefringent or consists of low-birefringent and isotropic parts mixed together, containing fragments of quartz, muscovite, alkali feldspar, plagioclase, biotite, chlorite, heavy minerals and metamorphic and magmatic rocks, as well as an opaque material. The EMPA data revealed an Fe-rich illite-like matrix and helped to identify the mineral nature of the inclusions. Local pottery production in bonfires or surface clamps is envisaged. Miocene illitic clays may have been used as raw materials, mixed with a small amount of sandy temper. The thermal changes revealed by OM, the modification of the XRPD peaks and the EMPA data suggest firing temperatures of between 800 and 850°C.

Modelling of experimental X-ray diffraction (XRD) patterns is used to determine the phase composition of partially dehydroxylated kaolinite samples. To identify unambiguously the presence of two or three phases in the heated kaolinite samples, the full range of their XRD patterns has to be analysed. Two different kaolinites, from Imerys (UK) and from Georgia (USA; KGa-21), were studied. The heating temperatures were selected to cover the entire range of dehydroxylation for both kaolinites (400–550°C for Imerys and 400–495°C for KGa-21). Two different dehydroxylation pathways were observed. At each stage of partial dehydroxylation, the kaolinite from Imerys consisted of the original, non-dehydroxylated kaolinite and of a fully dehydroxylated phase, metakaolinite. During partial dehydroxylation of kaolinite KGa-21, each product formed at a given heating temperature consisted of three phases: the original kaolinite; a dehydroxylated phase, metakaolinite; and a phase with diffraction features corresponding to a defective kaolinite-like structure. To determine the content of metakaolinite in a partially dehydroxylated specimen, its experimental XRD pattern was reproduced by the optimal summation of the diffraction patterns of the initial kaolinite and metakaolinite. A procedure that reveals the basic diffraction features of the third phase is suggested. The XRD patterns and thus the structures of the metakaolinites formed after dehydroxylation of the Imerys and KGa-21 samples differ substantially. The conventional determination of the initial kaolinite and metakaolinite contents in partially dehydroxylated kaolinite based on the analysis of basal reflections and weight losses may lead to overlooking the formation of the intermediate phases.