The search for sufficiently high-quality clays for use in the tile industry represents a significant challenge. This study aimed to prepare Muttalip green clay tiles with flexural strengths adhering to the TS EN 1304:2016 standard. Muttalip green clay was subjected to sieving, vacuum pressed, dried and then baked to obtain galette tiles. The tiles were analysed subsequently using optical techniques, including X-ray diffraction, X-ray fluorescence spectrometry and field-emission scanning electron microscopy. The influence of various firing temperatures (900, 950 and 1000°C) on the flexural strength of the tiles was also investigated. The tiles obtained at 950°C exhibited a maximum flexural strength of 153.91 kg cm–2. Fourier-transform infrared spectroscopy revealed that the tiles reflect ultraviolet A radiation and absorb infrared radiation. Muttalip green clay is a suitable material for preparing tiles for roofing applications.

La composition minéralogique de la phase <2 µm de la croûte d'altération de teinte pâele et de quelques millimétres d'épaisseur, développée sur les faces des prismes basaltiques de Roudadou, près d'Aurillac, Cantal, a été étudiée par plusieurs techniques: RX, analyse thermique différentielle, thermogravimétrie, spectroscopie infra-rouge entre 600 et 200 cm−1, mesure des surfaces totales. Cette phase fine est constituée d'une fraction non cristalline relativement réduite et surtout de minéraux argileux cristallisés, parmi lesquels l'imogolite est largement dominante (50%), accompagnée de l'halloysite (30%). Parfois une smectite compléte ce cortège argileux. A notre connaissance, l'imogolite n'avait jamais été identifiée parmi les produits d'altération superficielle des roches volcaniques du Massif Central.

Study of “tierras de Lebrija” by chemical, dehydration curves, d.t.a., X-ray and electron microscopic methods indicates the composition of these Pliocene sediments to be approximately equal quantities of attapulgite and illite.

Experimental studies of reactions between water and kaolinite, kaolinite + quartz, kaolinite + quartz + muscovite and natural kaolinitic mudstones (Jurassic Draupne Formation; Norwegian North Sea; Rhaetic Westbury Formation, SW England; Tertiary ball clay, SW England) at 50 MPa and 150°C or 200°C have demonstrated that quartz saturation can be achieved readily at 200°C At 150°C quartz saturation is achieved for natural mudstones, but not for mineral mixtures because of slow reaction kinetics. Geochemical solution modelling demonstrates coincidence between observed fluid compositions and those expected for the solid mineral assemblage. In addition to inorganic solutes, organic acid anions including citrate are reported as products in experiments with natural mudstones (especially the Draupne Formation). Fluids supersaturated with respect to quartz are unlikely to be developed from mudstones which lack smectites or amorphous silica.

The matric potential of water in gels of five-sixths neutralized aluminium montmorillonite (bentonite) and aluminium kaolinite changes during periods of shear and periods of rest. Shear increases the potential of water in bentonite gels, and in kaolinite gels containing little water, but decreases the potential in kaolinite gels containing more water. All these effects can be explained by changes in the curvature of water films at the gel-air interface. The difference between thixotropic and dilatant behaviour is the increasing and decreasing of the water potential on shearing. In dilatant pastes of silt-size particles, and for which the effects of electric charges are small, the pressure deficiency can reach large values after an increase in pore space, and this suffices to explain the characteristic features of dilatant behaviour.

The surface properties of wet-ground muscovite were studied by thermodynamics of water adsorption. The surface appears to be covered by contaminating material, probably organic, which is strongly held; it was not removed at 350° C and under a vacuum of 10−4 torr. Attention is directed to the difficulty of maintaining freshly made silicate surfaces without contamination and to the importance of surface conditions in the interpretation of silicate properties which involve surface phenomena.

En el miembro basal de la Formación Utrillas, que aflora en las cercanias de Nuévalos, se ha localizado un nivel constituido por ilita, montmorillonita, natrojarosita, caolinita, cuarzo y materia carbonosa.

Se aportan datos de análisis químico, termodiferencial, termogravimetrico, microscopico y de difraccion de rayos X de la natrojarosita.

Se le atribuye a dicho sulfato un origen sedimentario por precipitación en un medio de aguas estancadas, desarrollado sobre materiales margo-yesiferos del Keuper. El hierro aportado al medio, la materia orgánica, y los iones procedentes de la disolución de las evaporitas Triasicas, provocaron las condiciones fisico-quimicas necesarias para la precipitación de la natrojarosita.

Los minerales de la arcilla son heredados, a excepcion de la montmorillonita que se la podria considerar paragenetica con la natrojarosita.

This work presents the synthesis of minerals with a layered structure in supercritical water/ethanol mixtures to decrease the critical coordinates of the solvent regarding water. Depending on the water/ethanol ratio of the solvent, we obtained three different minerals adopting an octahedral brucitic sheet: (1) without a Si-tetrahedral sheet (O); (2) associated with one Si-tetrahedral sheet (T-O); or (3) intercalated between two Si-tetrahedral sheets (T-O-T). We have thus shown that ethanol in a supercritical water/ethanol mixture changes the solubility of silicon with a direct consequence on the formation of the tetrahedral silicon sheets and thus makes it possible to control the structure of the synthesized layered material.

This study examines the effect of German camomile (Matricaria camomilla L.) cultivation on the weathering of minerals present in the clay fraction of five different soil series modified or not unmodified (control) with cattle manure. A factorial experiment was performed in a randomized complete block design (RCBD) with three replications. At harvest time the rhizosphere soil was separated from bulk soil and the mineralogy was examined by X-ray diffraction (XRD). Trioctahedral chlorite transformed to hydroxy-interlayer vermiculite (HIV), while kaolinite disappeared. The presence of HIV was identified by an increase in the intensity ratio of the 1.0 and 1.4 nm peaks after Na-citrate pretreatment and K-saturation. It is suggested that Al3+ is released during dissolution of kaolinite and subsequently enters into the interlayer sheet of chlorite, and consequently the brucite layer disappears. This was verified by a significant Mg2+ increase in the soil solution in three out of five experiments at harvest time compared to pre-planting. The pots amended with manure showed the same changes as the pots without manure. The results of this study may explain the presence of unexpected clay minerals in regions with unsuitable conditions for their formation.

The objective of this research was to study the cellulose addition effect on the geopolymerization of heated clay. The clay, composed of illite, plagioclase and kaolinite, was heated at 700°C for 2 h and mixed with cellulose (up to 10 mass%). The mixtures were NaOH-activated, and shaped samples were aged at 83°C for 30 days. The cured samples were investigated by using X-ray diffraction, Fourier-transform infrared spectroscopy and scanning electron microscopy. The influence of the cellulose addition on the mechanical/physical properties was also evaluated. The results showed that zeolite ZK-14, hydrosodalite, sodium carbonate and a geopolymer composed of poly(sialate) units were formed in all cured samples. The relative amounts of zeolite and metakaolin evolved antagonistically, whereas that of illite slightly decreased with increasing cellulose content. Metakaolin and illite were involved in the geopolymerization process. Cellulose addition led to the improvement of the flexural strength of the samples and to porosity reduction. By contrast, water absorption was increased. The positive effect of cellulose on sample performance is explained on the basis of hydrogen bonding between the functional moieties of cellulose and the active sites of sample constituents, namely zeolites, metakaolin, illite and the geopolymer. As a filler, zeolite probably contributed to sample strengthening, and the detrimental impact of Na-carbonate was insignificant. Based on the results obtained, the composites could be used as binders for brick manufacturing or as lightweight mortars.

The mineral present in most clays used in the fine ceramics industries is kaolinite. Both china clays and ball clays consist essentially of this mineral in association with quartz and some form of mica. There is some evidence for the presence of traces of montmorillonite in certain of the Cornish china clays (Clark, 1950) and a method of estimating this has been reported (Parker, Warren and Morcom, 1951). Work at the British Ceramic Research Association has shown that many Dorset ball clays are largely composed of a disordered kaolinite similar to Brindley and Robinson's fireclay mineral (1947); such clays are frequently more plastic than other ball clays and show high mechanical strength. Other ball clays contain normal kaolinite of finer particle size than the average china clay and in exceptional cases may show strengths equalling those of the disordered kaolinite.

Hydrogen forms of natural mordenite and clinoptilolite were used as catalysts for styrene oligomerization and as matrices to hold the resultant oligomers in order to prepare intense and light-resistant pigments. In contrast to synthetic zeolites of similar pore sizes (mainly H-ZSM-5, H-mordenite), the natural zeolites did not form products with an intense (pink) colouration. H-mordenite samples treated with styrene developed some colour due to styrene oligomers (the chromophore) whereas, in treated clinoptilolites, colour formation was negligible due to the lack of access of styrene molecules into the elliptical channels. The results of catalytic tests for cracking of cumene (cumene and styrene have similar molecular sizes) were consistent with the styrene oligomerization results. They indicate a noticeable catalytic activity with natural H-mordenite and a lack of activity with clinoptilolite. On the other hand, catalytic tests for propan-2-ol decomposition indicate a high activity with both natural zeolites, which confirms the presence of acid sites and their accessibility to small alcohol molecules.

EPR spectroscopy was used to provide evidence for the existence of vanadium(IV) in two samples of rectorite. Possible sites for the vanadium are the tetrahedral and octahedral sites in the 2:1 layers and the non-exchangeable interlayer sites in the paragonite part of the structure. Consideration is given to each of these possibilities but the experimental evidence is insufficient to identify conclusively the location of the vanadium. Since substantial amounts of vanadium(IV) were present in the only well-defined rectorite samples obtainable, it is possible that the formation of rectorite is facilitated by the presence of vanadium.