Kaolin deposits >10 m thick overlie unconformably a Mesozoic ophiolite sequence at Jabal Humr, Masirah Island, Oman. The clay's mineralogical and chemical composition, plasticity and moisture content were measured to determine its genesis and suitability for commercial usage. The clay-rich raw material contains 76–94% kaolinite and varying amounts of quartz (micro sheets coating kaolinite) and calcite as well as secondary sulfates. The mode of occurrence, an associated shallow-marine iron oolite/pisolite unit, various secondary minerals which can only form in a gossan environment (oxidation zone of a much older sulfide deposit), and minerals such as gypsum that are highly unstable within a laterite, have led to the conclusion that the Jabal Humr kaolinite deposit cannot have the lateritic origin that has been suggested previously. Rather, it must have formed in a coastal marine environment with a subsequent strong geochemical overprint from the underlying gossan environment, after being enveloped by Tertiary carbonates. A high plasticity and its light colour after firing indicate that this material is suitable for industrial use, especially in pottery. Occasional high contents of up to ∼25% extremely fine-grained quartz (sheet-like, <50 nm thick) reduce the need for quartz addition during the processing for ceramic materials; such natural kaolinite-quartz mixtures already produce a suitable blend of materials. The possible occurrence of spalling during or after firing, caused by the sporadic presence of accessory calcite, can be avoided by by further addition of quartz which leads to the formation of calcium silicate.

The low-frequency conductivity of aqueous kaolinite suspensions has been measured as a function of volume fraction and concentration of KCl, K2SO4 and BaCl2, respectively. These measurements were interpreted with a theoretical model accounting for surface conductivity and particle shape. For the first time, an internally consistent data set was established by measuring all parameters necessary to solve the relevant equations. The simultaneous availability of surface conductivity, surface charge density and diffuse layer charge density permitted the estimation of counterion mobilities in the stagnant layer and a consistency check for the evaluation procedure of the conductivity experiments. In agreement with current literature results, monovalent counterions were found to have a Stern layer mobility similar to their bulk mobility, whereas the mobility of divalent counterions in this layer is reduced by a factor of ∼2.

Hydration reactions are known to affect rock or aggregate stability in construction; laumontite is not usually considered to be a ‘problem-mineral’ though drill cores from the very low-grade metamorphic altered andesites and volcanoclastic rocks from Central Chile showed detachments of shotcrete in a tunnel exposed to periodic water flow, with expandable clay phases presumed to be responsible for the observed failure. Abundant laumontite detected in the cores may also be responsible for the detachment, however, resulting from the structural expansion and contraction in response to hydration and drying. Clay reactivity in construction projects is often tested on site by 30 days of ethylene glycol exposure, but adequate monitoring options for laumontite are not deployed. Options for laumontite characterization involving a combination of water immersion and slaking and modified oedometer-based expansibility tests were used here to observe the response to laumontite expansion pressure. All tests were formulated considering minimal implementation efforts for building sites or the easy availability of analytical and testing facilities.

Laumontite was identified by optical microscopy, semiquantitative X-ray diffraction, and automated mineralogical analysis. A combination of the latter two methods provided reliable information about the presence of sub-microscopic laumontite and a visual impression of the textural arrangement of the zeolite in the rock.

A slaking test based on four cycles of immersion followed by drying and final application of weight (simulated overburden) is best suited to indirect detection and for demonstrating rock reactivity due to the presence of laumontite. Rocks with laumontite show expansion when crushed, recompacted and fitted into an oedometer, but mineralogical information is required for adequate interpretation of the results.

The present study focused on the assessment and possible applications of the clay from the Miličinica deposit, western Serbia. X-ray diffraction (XRD), Infrared (IR) spectroscopy, Inductively Coupled Plasma Optical Emission Spectrometry (ICP-OES), Differential Thermal Analysis and Thermogravimetry (DTA-TG) and High Temperature Microscopy (HTM) were used to characterize the clay in question. The physical properties determined were colour, plasticity, specific surface area, particle-size distribution and cation exchange capacity (CEC). Clay minerals are the main phases in the samples studied, with illite being the predominant phase and kaolinite being present in variable amounts. Quartz, feldspars, carbonates and iron-bearing minerals were also detected. Varied technological behaviours were expected because of the mineralogy (illite and iron contents), average grain size (0.6–0.7 µm), specific surface area (≈60 m2/g) and plasticity index (≈13%). The classification of the clays studied, based on the main characteristics and using appropriate diagrams, suggests that they are easily adaptable for ceramic processes.

Polycyclic aromatic hydrocarbons are increasingly widespread pollutants introduced into the environment via oil spillage and incomplete anthropogenic combustion of fossil fuels. In this work, the capacity of stevensite and sepiolite to adsorb phenanthrene (PHE) has been evaluated experimentally by batch testing. Both clay minerals are distributed widely in the Madrid Basin, are of low cost and can be applied with minimal environmental impact. In the context of few previous studies, adsorption isotherms have been developed to understand the adsorption mechanisms and were fitted to the Freundlich and linear models with virtually the same results. Although stevensite showed greater adsorption capacity than sepiolite, the isotherms were constructed for equilibrium concentrations up to 0.8–1.0 mg/L due to the low solubility of PHE in water. When compared to other adsorbents the ability of stevensite to retain PAHs should be examined further in order to add and complement novel functions in reactive barriers.

The Çankırı Basin is one of the largest Cenozoic basins in Central Anatolia, Turkey and contains possible economic hydrocarbon and evaporite reserves. Gypsum is the dominant mineral in the evaporite-bearing Pliocene deposits of the Çankırı Basin. In claystones, the abundance of smectite, dolomite, illite/mica and chlorite in association with minor amounts of mixed-layer chlorite-smectite, mica-vermiculite, amphibole, serpentine, quartz and feldspar together indicate an alkaline environment. Minor kaolinite is also present in some clay samples. Smectite is both detrital and authigenic. Palynological analysis revealed the existence of a mixed forest (Pinus, Cathaya, Tsuga, Cedrus, Abies, Quercus, Ulmus, Juglans, Pterocarya, Acer, Carya, Carpinus, Fagus) dominated by Pinus with a widespread herbaceous understory (Poaceae) interspersed sparsely with open areas occupied by Asteraceae. This flora reflects warm-temperate and humid climatic condition. δ13C analyses have shown that the vegetation was dominated by C3 plants.

Ordovician clastic rocks of the Antalya unit in SW Turkey bear mineralogical/geochemical evidence of Triassic extensional rift timing and spatial relations. The crystal chemistry of the phyllosilicate assemblages (illite, chlorite, kaolinite, mixed-layer illite-smectite, chlorite-vermiculite and chlorite-smectite) is consistent with the rock experiencing a multi-generational burial history. The appearance of kaolinite and illite-smectite-bearing rocks in the Antalya unit is characteristic of diagenetic-anchimetamorphic conditions and is of higher grade than their anchi-epizonal equivalents in other regions of the Tauride belt. Illites and chlorites are of both detrital and authigenic origin, whereas I-S and kaolinites are authigenic. Detrital micas have been altered to chlorite and K-white mica stacks in which relicts suggest the chlorites were derived from detrital biotites. The broad X-ray diffraction illite peaks show that they are composed both of illite and illite-smectite. Na,K-mica and paragonite occur within the chlorite-mica stacks as replacements of muscovite, probably driven by Na-rich solutions. The authigenic clays were formed within the microporous matrix and the interplanar spaces of {001} planes of chlorite-mica stacks, with textures independent of the bedding and foliation planes of the rocks. The authigenic chlorites exhibit higher Si and Fe and lower Mg contents than their detrital counterparts. Authigenic chlorite thermometry indicates rift-related temperatures of 50–150°C, whereas pre-rift detrital chlorites formed at temperatures of  >200°C. Authigenic illite and illite-smectite are phengitic in composition and contain more Si, Mg, Fe and Ca and less Al and K than detrital K-white micas. The textural, mineralogical and chemical characteristics support the hypothesis that the mineral assemblages were a result of a two-step mode of formation with diagenetic overprints of previously anchizonal rocks in extensional basin conditions.

Because of the current need for new landfill sites in Ankara, the suitability of Ankara Clay as a liner material for landfill sites was investigated. A mineralogical and geotechnical database was created by compiling the results of previous tests by the present authors as well as those of tests performed in the present study. The mineralogical properties of the samples were investigated by X-ray diffraction, scanning electron microscopy and methylene blue adsorption. The cation exchange capacities (CEC) of the samples vary from 12 to 35 meq/100 g soil and the dominant clay minerals are illite, smectite and kaolinite. The geotechnical properties of the Ankara Clay samples that were assessed included specific gravity, the Atterberg limits (plastic limit, liquid limit, plasticity index), particle-size distribution, compaction properties (i.e. maximum dry density and optimum water content) and hydraulic conductivity. Because the hydraulic conductivity of the samples was lower than the acceptable limit of 1 × 10−9 m/s, it follows that, from a geotechnical perspective, Ankara Clay is a suitable material for use as a compacted clay landfill liner. The relationships between the mineralogical and geotechnical parameters that were investigated by regression analysis indicated that the hydraulic conductivity of the compacted soil samples decreased with increasing plasticity index, clay content, CEC, smectite content, smectite to illite ratio and decreasing illite content. According to the specifications for field construction of compacted clay liners, Ankara Clay is suitable for compaction in the field.