The Şahin-village clay deposit, situated in the vicinity of Kütahya, western Turkey, has a promising reserve suitable for tile production. In order to evaluate its potential use, 27 clay samples were collected and their mineralogical, chemical, firing and technological properties were evaluated. The reaction of samples with dilute HCl, dispersion in water and their swelling properties were determined. Mineral identification studies were conducted using X-ray powder diffraction (XRD), differential thermal analyses (DTA) and scanning electron microscopy (SEM) techniques. Analysis showed that clay minerals are illite, kaolinite and montmorillonite. Non-clay minerals are quartz, muscovite, microcline and goethite. The clay samples consisted mainly of SiO2 and Al2O3 corresponding to about 81–83% (average) because of the presence of clay minerals and quartz, accompanied by a significant amount of iron oxide. Mineralogical, chemical, thermal analysis and technological tests showed that the clays from Şahin village could be used for stoneware tiles, tile and brick-making.

No comprehensive study has yet been conducted to determine the chronostratigraphic distribution of palygorskite in the Tertiary sediments of Iran. Thirty sediment samples of different Tertiary epochs were taken, based on the field observations and geological maps. The clay fraction of samples was then investigated by X-ray diffraction (XRD), transmission and scanning electron microscopy (TEM and SEM), and inductively coupled plasma mass spectrometry (ICP-MS). Results showed that sediments of the Miocene and Pliocene had large amounts of palygorskite whereas no trace of this mineral was found in the sediments from the Palaeocene, Eocene and Oligocene. Geochemical analyses revealed that sediments younger than the Oligocene had greater amounts of soluble Mg and H4SiO4 and a higher pH than those of the Palaeocene and Eocene. The stability diagram of the smectite-palygorskite system suggests that smectite is unstable and transforms to palygorskite in Neogene sediments. The SEM micrographs showed palygorskite as interwoven fibrous mats, coatings, pore-fillings and pore-bridging material in Neogene sediments. This textural evidence suggests a direct chemical precipitation of palygorskite by dissolution of silicates under the alkaline conditions. The results also suggest that geochemical conditions in the Early Tertiary era, represented by deep-sea conditions in central Iran, were not apparently favourable for palygoskite formation until the Late Oligocene.

In this study, natural bentonite was modified with hexadecyltrimethylammonium (HDTMA) bromide to obtain organobentonite (HDTMA-bentonite). Bentonite and HDTMA-bentonite were then characterized using XRD, XRF, SEM, FT-IR, thermogravimetric (TG) analysis, elemental analysis and Brunauer-Emmett-Teller (BET) surface area techniques. The HDTMA+ cation was found to be located on the surface and enters the interlayer spaces of smectite according to the XRD and SEM results. FT-IR spectra indicated the existence of HDTMA functional groups on the bentonite surface. The BET surface area significantly decreased after the modification due to the coverage of the pores of natural bentonite. After the characterization, the adsorption of a textile dye, Reactive Blue 19 (RB19), onto bentonite and HDTMA-bentonite was investigated. The maximum adsorption capacity of HDTMA-bentonite for RB19 was 502 mg g-1 at 20°C. The adsorption process followed a pseudo-second-order kinetic model and it was exothermic and physical in nature.

Early Cretaceous glauconite from the Xiala section, southwestern Tibet, China, was investigated by petrographic microscopy and scanning electron microscopy (SEM), X-ray diffractometry (XRD), Fourier transform infrared (FTIR) spectroscopy, and electron probe microanalysis (EPMA). The investigations revealed that the glauconite in both sandstones and limestone is highly evolved. The glauconite in sandstone is autochthonous, but in limestone it may be derived from the underlying glauconitic sandstone. Based on analyses of the depositional environments and comparisons of glauconite-bearing strata in Zanda with sequences in adjacent areas, we conclude that the glauconitization at Zanda was probably associated with rising sea levels during the Late Albian, which represent the final separation of the Indian continent from the Australian-Antarctic continent. After the separation of the Indian continent from the Australian-Antarctic continent, cooling of the Indian continent resulted in subsidence and northward subduction of the Indian plate. A gradually rising sea level in Zanda, located along the northern margin of the Indian continent, was the cause of the low sedimentation rate. Continued transgression resulted in the occurrence of the highly evolved glauconite in this area.

The aim of this research was to assess the potential application of the Late Cretaceous levels as raw material for the production of ceramic tiles. Mineralogical, chemical and grain size distribution studies were carried out on four clays sampled at different sites in the Tunisian Central Atlas. Clays are mainly composed of phyllosilicates, usually illite and kaolinite. Quartz, feldspars and dolomite were also detected.

Tiles were prepared by pressing clay bodies at 250 bar and then firing at different temperatures following industrial conditions as closely as possible. Thermal analysis showed the influence of mineralogical composition and grain size distribution on the material behaviour during firing. The physical properties of fired tiles were obtained from specific tests in accordance with international standards (ISO), i.e. the firing shrinkage, water absorption, apparent density and flexural strength. The development of physical properties indicates an optimal firing range between 1050–1150°C. Results demonstrate the potential of Late Cretaceous materials as raw materials for the production of ceramic tiles.

Magnetite-rich waste from a niobium mine near Araxá, State of Minas Gerais, Brazil, was heated to 500°C and 1000°C under an O2 atmosphere. The original waste and its oxidized products were characterized by energy-dispersive X-ray spectroscopy (EDS), X-ray powder diffraction (XRD), room-temperature 57Fe Mössbauer spectroscopy, thermogravimetric analysis (TG) and temperature-programmed reduction (TPR).

Semiquantitative analyses by EDS and quantitative chemical analyses showed the waste to be constituted primarily of Fe with minor amounts of Ti, Ba, Al, Si, Nb, Mn, S and P. Mössbauer and XRD showed the waste to consist predominantly of magnetite and hematite. The magnetite content decreases when the temperature increases due to its direct conversion to hematite. However, at 500°C only 10 wt.% of original magnetite was converted to hematite, confirming the high stability of this magnetite, which could still be detected at 1000°C. The TG profile shows no significant weight gain on heating, indicating a high stability of the magnetite. The TPR profiles show that the hematite in the waste is sintered after treatment at 1000°C and the reduction peaks are consequently shifted to higher temperatures. This high thermal stability is attributed to a moderate isomorphous replacement of Fe by other cations present in the Nb mining waste.

Natural zeolitic tuff from Brus (Serbia) consisting mostly of clinoptilolite (about 90%) has been investigated for the reduction of the Mg concentration in spring water. The sorption capacity of the zeolite is relatively low (about 2.5 mg Mg g-1 for the initial concentration of 100 mg Mg dm-3). The zeolitic tuff removes Mg from water solutions by ion exchange, which has been demonstrated by energy dispersive X-ray analysis (EDS). The extent of ion exchange was influenced by the pH and the initial Mg concentration. Kinetic studies revealed that Lagergen's pseudo-second order model was followed. Intra-particle diffusion of Mg2+ influenced the ion exchange, but it is not the rate-limiting step. Rather than having to dispose of the Mg-loaded (waste) zeolite, a possible application was tested. Addition to a wastewater with a low concentration of Mg showed that it could successfully make up for the lack of Mg micronutrient and, accordingly, enabled the growth of phosphate-accumulating bacteria A. Junii, increasing the amount of phosphate removed from the wastewater.

The present occurrence is the only deposit among those found in Eskişehir province containing both sepiolite and palygorskite in economic amounts. To describe the geology, mineralogy and genetic relationships, two representative measured sections were examined by field work and XRD, XRF and SEM analyses. Sepiolite and palygorskite occur in a ∼40 m thick part of Pliocene sequence where saponite is also found. These minerals appear in ascending order as: palygorskite, saponite, saponite + palygorskite, sepiolite and sepiolite + palygorskite, frequently in association with dolomite. Chemical precipitation from the alkaline lake environment under semiarid or arid conditions was the main process resulting in sepiolite, palygorskite and saponite formation. Of these, saponite and palygorskite were formed when the lake water was rich-in Al and Fe. Changes in pH may have controlled whether saponite or palygorskite could be formed. Palygorskite was also developed by transformation from saponite during diagenesis.

Different types of dioctahedral smectites (nontronite, beidellite, montmorillonite) were investigated by X-ray fluorescence analysis (XRF) and Fourier transmission infrared spectroscopy (FTIR). Starting with the chemical composition of the octahedral sheet, the occupancies within the octahedral sheet were adjusted by computer simulations to fit the occupancies derived from FTIR. For both cis-and trans-vacant smectites the AlAl and FeFe pairs are mainly randomly distributed but seem to be aligned along OH-bonded directions. Relative to the chemical composition, AlFe pairs are enriched in cis-vacant smectites and depleted in nontronites. This behaviour can be explained by the necessity to dehydrate and hydrolyse cations when they become incorporated into the structure during crystal growth. The first and second hydrolysis steps are necessary for incorporating cations in trans-vacant smectites, whereas only the first hydrolysis step is necessary for cis-vacant smectites. The corresponding difference in energy may explain why mostly cis-vacant smectites occur in low-temperature environments.

This study examines part of the thick palaeoweathering mantle that formed on the northern area of the Spanish Central System. The study of a compound profile indicates that despite weathering processes, the primary structure of the metamorphic rocks is preserved, and is only partially lost in some intervals of the upper part of the compound profile. Macro/micromorphology, mineralogy and geochemical changes within the profiles revealed two weathering paths. In the first path, Fe-chlorite weathered to chlorite-smectite mixed-layer/smectite/kaolinite+ iron oxides. In the second path, biotite and/or muscovite weathered to kaolinite + iron oxides. The profiles show a progressive decrease, from base to top, in mica and mixed-layers and an increase in smectite and kaolinite. Thus, the profiles only comprise the lower or intermediate zones of the weathering mantle. The weathering occurred under humid climates; the lower zones of the profiles were poorly drained, whereas the topmost zones were better drained and more oxidizing. The results obtained indicate that detailed mineralogical studies are very useful to reconstruct the characteristics of the weathering mantles, and as palaeogeographic and palaeoclimatic indicators.

The kaolin deposit at the Adelita mine, located in the province of Rí;o Negro (Patagonia, Argentina), was studied. Petrographic studies on thin sections and chemical analyses of major, minor and trace elements on bulk samples were carried out. The kaolin content of the rock ranges from 31% to 65%. The mineralogy of the working front, which is about 45 m thick, varies from the upper zone, where the rock is strongly silicified, stained with iron oxides and carbonated, grading downwards to a kaolinized zone, with a quartz-kaolinite-dickite assemblage with relict lithic particles and a smaller amount of iron oxides, and ending in the deepest zone where dickite, alunite, diaspore, quartz and scarce associated kaolinite occur.

The kaolin mineralogy was determined by SEM, XRD, DTA-TG, IR and δ18O and δD isotope analyses. The S, Ba and Sr contents are enriched during hydrothermal alteration, whereas Cr, Nb, Ti and lanthanide elements are concentrated mainly during weathering. The (Ba+Sr) concentrations in the samples studied vary between 600 and 6000 ppm and (Ce+Y+La) between 2 and 150 ppm; (Cr+Nb) remains constant for all the samples, whereas (TiO2+Fe2O3) is below 0.3%. In the hypogene deposits P2O5 is also more abundant and increases with the degree of alteration. Chondritenormalized rare earth element diagram shows a marked enrichment in LREE relative to HREE, with negative europium anomalies and D18O values range between 3.8‰ and 7.7‰ and δD between –123‰ and –103‰, suggesting that kaolin formed from the hydrothermal alteration of rhyolitic tuffs.