Weathered soil material derived from tectonically emplaced serpentinized ultrabasic intrusive rocks of southern Cameroon has received considerable attention from mining companies due to its extractable-metal (i.e. Ni, Co) potential. As these cations can be incorporated into Fe oxides, it was deemed appropriate to study the mineralogical assemblage of a highly weathered serpentinite soil profile from the area. This study focuses on the different Fe-oxide phases, which were investigated using 57Fe Mössbauer spectroscopy, showing goethite and hematite as the dominant Fe oxides throughout the weathering profile. These minerals, in association with gibbsite and kaolinite, indicate an advanced degree of weathering. The clay fraction of the ‘Lower Limonite’ layer, above the saprolite and at a depth of 7 m, is very rich in goethite, whereas hematite and magnetite are almost absent. Above this layer, the hematite content in the fine-earth and clay fractions increases upwards, while the goethite content remains constant. The significant substitution and change in the particle size of the goethite and the poor crystallinity of hematite, as indicated by the hyperfine parameters and XRD, suggest that the upper material evolved under different pedological conditions compared to the deeper layers. The mixed composition of the upper layers (above 7 m), which contain muscovite and a relatively chaotic distribution of trace elements, suggests ancient mica-schist capping and possibly different cycles of erosion and pedimentation.

A set of seven soils representative of types of considerable pedological importance in the Umbrian region of Italy have been examined by petrological and clay mineralogical methods in order to supplement previous data upon field and chemical characteristics (Lippi-Boncambi, 1950). Some basic data upon colour, locality of the sample examined, parent material, rainfall (P), temperature (T), rain factor (P/T—see Lang, 1915) and pH are summarised in Table 1. It will be noted that (a) the soils form an interesting colour group ranging from red through intermediate colours to yellow and then through brown to black, (b) all except one are derived from calcareous rocks, and (c) all except one are neutral to alkaline in reaction.

The aggregation of three cationic dyes (CD), crystal violet (CV), Nile blue (NB) and rhodamine B (RB) in aqueous solution was studied by visible absorption spectrophotometry and compared with methylene blue (MB). The distribution of the dye species (monomers, dimers, trimers, and tetramers) in aqueous solutions with different concentrations of dye was calculated using equilibrium stepwise aggregation constants Kn. These cationic dyes were intercalated into montmorillonite (SAz-1) and its reduced charge form (RC-SAz(210)) prepared by heating lithium montmorillonite (Li/SAz-1) at 210ºC. The fluorescence of fully saturated CD/SAz and low-CD loaded CD/RC-SAz(210) complexes was studied. Visible absorption spectra of CD aqueous solutions and visible absorption spectra and X-ray diffraction patterns (d001) of the CD/SAz and CD/RC-SAz( 210) solid complexes were obtained and evaluated. Large fluorescence intensities were found for CV/RC-SAz(210) and NB/RC-SAz(210) complexes in the same way as for the complex of methylene blue with reduced-charge montmorillonite MB/RCM(210) described previously.

A simple jig is described for the construction of a model of the muscovite structure in which the distorted hexagonal, i.e., ditrigonal, arrangement of the basal oxygens of the tetrahedra is accurately represented. The model is of the packing kind as opposed to the ball-and-spoke kind and demonstrates the advantages of this type of model, which would be more generally used if transparent plastic balls were available commercially.

In the laboratories of the Geological Survey of Sweden we have for many years used an acid-resistant, stainless steel filtering funnel to prepare ‘oriented’ clay mounts for X-ray diffractometry. The funnel consists of three parts (left and centre foreground of Fig. 1). The circular plate is porous and made of sintered stainless steel and serves as a support for a 47 mm diameter membrane filter. The cylinder is manufactured in two different sizes, 250 ml and 600 ml. The funnel is generally mounted on a suction flask but when the filtrate has to be analysed a suction cloche is preferable.

When many mounts have to be prepared the use of a manifold is practical and time saving. We have adapted the Sartorius six-branch manifold and added a transition tube of stainless steel (right foreground of Fig. 1), threaded to fit the manifold outlet and tightened through a gasket. The funnel itself is mounted on the tube through a rubber stopper. Suction is by a small pump (25 l/min, 0·15 kW). A suction flask is placed between the filter stand and the pump to collect the combined filtrates (Fig. 2).

An homogenous intercalated compound of dioctahedral 1:1 clay mineral with cesium chloride was prepared by immersing an homogeneous 8.4 Å hydrated nacrite in a CsCl-saturated solution. The nacrite/CsCl complex obtained was studied using X-ray diffraction and thermogravimetric analysis (TGA). The best agreement between the observed and the simulated ρ(z) (R = 7%) was obtained with one Cl− ion, one Cs+ ion and onewater molecule (per half-unit cell). The cation was located near the oxygen atom plane, while the anion was located near the hydroxyl groups of the adjacent layer. The number of the species intercalated in nacrite/CsCl was confirmed by TGA analysis. The best agreement between the calculated and the experimental hkl reflections, with h and/or k ≠ 0, corresponded to a stacking of 70% and 30% for T1 = −0.35a − 0.20b + 10.50n and T2 = +b/3 + 10.5n, respectively. These results indicate that the surface hydroxyls form hydrogen bonds with Cl− ions. The Cs+ ions are situated near the ditrigonal cavities of the tetrahedral sheet and they interact with the surface oxygen atoms whereas the H2O molecules interact with the intercalated species.

The techniques previously employed in this laboratory for removing free iron oxide from soil clays were the acid ammonium oxalate and the aluminium-ammonium tartrate methods (Tamm, 1922; Dion, 1944). Since both had disadvantages, especially when determining the iron by sodium salicylate (Scott, 1941), the use of sodium hydrosulphite, Na2S2O4, (Galabutskaya and Govorova, 1934; Deb, 1950) was fully investigated in the hope that it might lead to the development of a satisfactory, completely inorganic procedure.

Deux questions sont abordées: (1) Une eau naturelle étant donnée, peut-on considérer qu'elle est en équilibre avec un minéral de formule connue? (2) Un ensemble homogène d'eaux naturelles étant donné, peut-on considérer que ces eaux sont en équilibre avec un minéral? Si oui, Peut-on proposer une estimation de la composition de ce mineral? Nous proposons une méthode pour répondre à chacune de ces deux questions. Cette methode est appliquée à l'estimation de minéraux argileux de formule générale SiaAlbMgcCadKeNafOn(OH)m. Les données utilisées sont des eaux de percolation, dans des colonnes de sols.

Surface excess isotherms were determined for the adsorption of 1,4-dioxan (DIOX), tetrahydropyran (THP) and tetrahydrofuran (THF) from binary solution with methanol (MeOH) on Al3+- and Cr3+-exchanged, montmorillonite containing different amounts of pre-adsorbed water. The isotherm type is dominated by the binary mixture whereas the amplitude, which follows the sequence DIOX > THP > THF, is further influenced by the exchange cation, Al3+ > Cr3+, and the water content of the clay. The sorption of DIOX and THP from MeOH exhibit a type IV isotherm in the Schay-Nagy classification on both cation-exchanged forms, whilst that of THF from MeOH is of type I and THF is the preferred adsorbate. The azeotropic point for the type IV isotherms is close to a 1:1 mole ratio for the samples dried at 120°C but when the samples are rehydrated at 12% r.h. following thermal pretreatment at 120°C the azeotropic point shifts in favour of the cyclic ethers DIOX and THP, making them the preferred component over a substantial portion of the composition range.

In this paper, the role of Cu in the adsorption of the cationic pesticide chlormequat (CCC) on montmorillonite is studied. The adsorption of CCC was measured in various media, e.g. water and aqueous solutions of NaCl, CaCl2 and Ca(NO3)2 at the same ionic strength (I= 0.01 mol l–1). The retention of CCC on montmorillonite in aqueous media is due principally to a cationic exchange process with inorganic cations which saturate the interlamellar positions on this mineral. However, the amount of inorganic cations liberated from montmorillonite was ∼15% less than the amount of CCC adsorbed. This indicates that not all the pesticide was adsorbed through cation exchange.

The adsorption of CCC in aqueous media decreased in the presence of a heavy metal, compared with metal-free treatment. This behaviour indicates competition between the two cations for interlamellar positions. The adsorption of CCC in the presence of Cu also decreased in electrolyte media with the effect being highest in the presence of Ca electrolytes. The maximum CCC diminution was ∼30%. However, the isotherms derived in CaCl2 and Ca(NO3)2 media at different Cu concentrations were close to each other, indicating that Ca from background electrolyte exerts greater competition than Cu for montmorillonite planar positions.

The observation of clayey matrix on a thin-section under polarized transmitted light allows the analysis of the clay particle arrangements, the measurement of their orientations in 3-D, and finally the cartography of the different orientation modes by using a simple image analysis system connected to the optical microscope. The method is based on: (1) the analysis of the shape evolution of the grey-level diagram vs. the rotating stage angles; and (2) the mathematical decomposition of these grey-level diagrams into elementary gaussian curves. For each identified orientation mode, the standard deviation of the grey values gives the dispersion index of the oriented particles around the axial plane. The 3-D representation is performed on the Wulff stereonet. The horizontal orientations are measured by simple rotation of the revolving stage and the dip angles are deduced from the peak displacements along the abscissa of the grey-level diagram during the complete rotation of the revolving stage. The quantifications (percentage, isotropy and distribution index) are performed after a thresholding operation of each orientation mode.

Pyrophyllite from a Triassic sedimentary formation from the Coastal Range of Chile has been investigated by transmission/analytical electron microscopy (TEM/AEM). The mineral assemblage includes pyrophyllite, muscovite, paragonite, a kaolin mineral, boehmite, rutile and hematite. The textures indicate that the protolith was a volcanoclastic rock. Petrographic evidence, chemistry, and the mineral assemblage suggest the intense leaching of the parent rock by a weathering process, before the metamorphic episode, to create the protolith for the pyrophyllite. Pyrophyllite always grows from the kaolin mineral, and both phases show close orientation relationships. The presence of parallel intergrowths of pyrophyllite and muscovite indicate that muscovite also grew from the kaolin mineral. Nevertheless, the composition of muscovite suggests that this phase must also form from another precursor, probably Al smectite. The AEM data and textural relationships between pyrophyllite and muscovite reveal the presence of two generations of muscovite and suggest that Na-rich muscovite recrystallized into a Na-free muscovite and paragonite.

Chemical, thermal, X-ray and statistical analyses were carried out on the clay fraction of the Bonarelli Horizon (Umbrian region, Central Italy) in order to investigate its origin. The vertical lithological sequence (organic carbon, siliceous and clay layers of varying colour and thickness) seems to change regularly, allowing the horizon to be subdivided into five sub-horizons (A to E). Sub-horizon B is clearly distinguishable from the others on the basis of the clay fractions. The presence of organic material and authigenic sulphates, constant chemical composition within a single sub-horizon, and regular repetition of the layers, show that the Bonarelli Horizon is the result of an alternation of anoxic events in a continental margin facies. A substantial contribution of volcanoclastic material is suggested for sub-horizon B.

The environmental conditions in Maritime Antarctica are more favorable to soil development than in continental areas, which is reflected in the content and type of clay minerals present. In this context, soil clay minerals of Fildes Peninsula, South Shetland Islands were studied with the aim of relating them to periglacial and paraglacial processes as possible indicators of initial pedogenic processes. In this work, textural, mineralogical and crystallochemical characterization of clay minerals as well as chemical and physical soil analyses were carried out. The soil samples represented various surface cover types present on Fildes Peninsula. All samples were composed mainly of clay minerals, plagioclase, quartz and minor zeolites and pyroxene. The clay mineral content was very variable and reached up to 63% w/w. The clay minerals present are mainly smectite, vermiculite, chlorite and minor kaolinite, mica, corrensite and interstratified illite–smectite, with smectite and vermiculite dominating in almost all of the samples. The primary minerals display chemical alteration, and smectite formed by alteration of plagioclase. The clay mineral types were related to the parent material, which was affected by low-grade metamorphism and hydrothermal alteration that transformed biotite and chlorite into vermiculite via interstratified chlorite–vermiculite. Furthermore, this process and/or ongoing surface weathering transformed vermiculite into smectite. The genetic relationship observed between vermiculite and smectite suggests progressive alteration and transformation into a phase with intermediate composition between vermiculite and smectite. Therefore, vermiculite could be at least in part the smectite precursor. Samples closer to the current Collins Glacier front are composed mainly of vermiculite, with the greatest chemical variation occurring where the soils were developed from a mixture of initially glacially transported volcanic rocks through periglacial and fluvial processes. The clay minerals from the centre and south of Fildes Peninsula are mixtures of montmorillonite and vermiculite, as well as of chlorite and corrensite in various proportions. The clay minerals in soils developed on the west coast are a mixture of Fe-rich montmorillonite and vermiculite.

In the petroleum industry, one of the most important functions fluids must perform is to carry cuttings efficiently. In this context, the contamination of drilling fluids represents a challenge to the industry because it alters the properties of these fluids. This work compares two drilling fluids (one palygorskite-based and the other polymer-based), evaluating the effects of contaminants on these drilling fluids and their ability to carry cuttings. A contaminant is considered to be any material that causes undesirable changes in the properties of the drilling fluid. Contamination of an aqueous drilling fluid by calcium hydroxide (Ca(OH)2) and brine can increase the filtrate volume, decrease the perforation rate and alter the rheological properties of the fluid. This work analyses the effects of contamination by Ca(OH)2 and brine on the properties of salted water-based drilling fluids viscosified with palygorskite. For comparison, tests were performed with a polymeric drilling fluid. The cutting-carrying capacity of these fluids was verified using the empirical correlations of Moore (1974), Chien (1994) and Walker & Mayes (1975). The results show that the drilling fluid with palygorskite is resistant to contamination with Ca(OH)2 and brine, presenting low filtrate volume values. The drilling fluid with palygorskite presented greater slip velocities than the polymeric drilling fluid. Regarding the cutting-carrying capacity, the drilling fluid with palygorskite presented positive transport ratio values (>0), making it suitable for carrying rock cuttings. However, the polymeric drilling fluid showed better performance in terms of cutting-carrying capacity.

There is growing interest in the use of natural materials as alternatives to medicinal products composed of chemicals. For this reason, it is important to study materials which fill this need (e.g. the formulation of peloids). Historically, the Azores archipelago has long been visited for its mud baths, mainly on São Miguel Island, where volcanic muds demonstrate beneficial properties. The volcanic muds are scarce, however. Thus, residual clay materials of Santa Maria Island were studied to assess their suitability for the formulation of peloids. The results of tests from 20 samples, collected from all over the island, presented evidence that they are very favourable for peloid formulations, due to their mineralogical, chemical and technological properties. The materials showed good potential for blending with the São Miguel volcanic muds. The deposits studied show extensive outcrops.

A brief description is given of modifications enabling high spacings to be observed.