Precise measurement of the content and the layer charge of illite and smectite is an important aspect of the mineralogical calibration of geophysical well logs and of the evaluation of mechanical and chemical properties of sedimentary rocks. Ate chnique for obtaining such measurements was developed during mineralogical studies of the Miocene clastic rocks from the Carpathian Foredeep. X-ray diffraction (XRD), chemical, cation exchange capacity (CEC), H2O sorption, and ethylene glycol monoethyl ether (EGME) sorption data were obtained for 65 samples of sandstones, shales and carbonates. The illite + smectite sum, involving all detected 2:1 minerals (smectite, illite-smectite, illite, glauconite and muscovite) was measured by XRD. The content of the illitic component was evaluated separately using % K2O and accounting for % K2O in K-feldspar. The content of the smectitic component was estimated from EGME retention using the reference data for a smectite standard, and from CEC assuming the smectitic layer charge of 0.41/O10(OH)2 (Środoń et al., in press). All these measurements produced very consistent results.

New chemical and structural data on sepiolite-falcondoite in garnierite veins from the Falcondo Ni-laterite deposits, central Dominican Republic, are reported. Samples of Ni-sepiolite-falcondoite vary in colour from whitish green to green depending on the NiO content (wt.%) and the amount of silica present. The texture is normally schistose and friable but samples with considerable quartz and/or amorphous silica are compact and hard. Back-scattered electron images indicate that the samples are composed of at least three generations of Ni-sepiolite-falcondoite. The extreme refined cell parameters for Ni-sepiolite-falcondoite vary from 13.400(2), 27.006(4), 5.273(1) Å to 13.340(3), 27.001(6), 5.267(1) Å (space group Pncn). As the Ni content increases there is a small reduction in the a parameter. Chemical compositions determined by electron probe microanalysis cover a large interval of the Ni-sepiolite-falcondoite solid solution (Fal3 and Fal77). Individual samples show a considerable range in composition with the widest range determined in one sample from 4.63 to 22.40 wt.% NiO.

The composition and particle morphology of diagenetic mixed-layer illite-smectite (I-S) in the shallow buried Ordovician Kinnekulle K-bentonite were studied to understand the process of illitization in the Baltic Basin. The same K-bentonite bed from 12 different locations in the Basin was sampled and analysed by means of X-ray diffraction (XRD), atomic-force microscopy (AFM) and K-Ar dating. Illite-smectite in the samples was identified as a highly illitic R1 type illite-smectite vermiculite (high-charge smectite) mixed-layer mineral with 63–78% illitic layers. Illite-smectite was characterized by log-normally distributed thin particles with an area-weighted mean thickness varying from 1.9 to 3.6 nm and 2.1 to 3.8 nm by XRD-PVP and AFM analysis, respectively. The K-Ar diagenetic ages of the mixed-layer minerals suggest an illitization age of 370 to 420 Ma that agrees with the latest phase of the Caledonian orogeny. Illitization of the Kinnekulle bentonite was probably driven by the intrusion of K-rich fluids.

The climatic history of the Dead Sea region during the Pliocene and its global connection are observed from climate-sensitive rocks and clay minerals of the Sedom formation. The Sedom formation consists of evaporative halitic rock salt units and calcareous shale units that were deposited in the Dead Sea Basin during the Pliocene. The precipitation of the rock salts took place in the hypersaline sabkha environment of the Sedom Lagoon. The extensive evaporative conditions are related to an extremely dry and warm arid climate at that time. In the arid climate, the influx of meteoric water by the drainage system of the Sedom Lagoon was limited and permitted a large concentration of lagoonal brine as well as a small rate of detritus transportation to the lagoon. Accessory sepiolite found in the rock salt appears to be neoformed from brine enriched with Mg and poor in Al under the extreme salinity condition. The small amounts of Al are in accordance with the small number of detrital minerals in the rock salts. The replacement in the deposition of the rock salt members with the calcareous shale members demonstrates a decrease in the salinity of the brine in the Sedom Basin and an increase in the deposition of detritus. The change in conditions was related to a period of deposition under a more humid climate where the erosion and the transport of detritus by the drainage system to the Sedom Basin was higher, causing the deposition of calcareous shales. Palygorskite found in the calcareous shales appears to be neoformed from brine enriched with Mg and containing Al in conditions of reduced salinity of the Sedom Basin. The larger amounts of Al are in accordance with the abundance of detrital minerals in the calcareous shales.

The depositional cycles of the Sedom formation, the cyclic fluctuation of the climatic-hydrologic conditions from an arid to a more humid climate and their correlation with sea-level fluctuations and transgression-regression cycles of the Mediterranean Sea seem to be a response to corresponding global interglacial and glacial periods during the Pliocene.

A bentonite sample from the Petreş ti deposit, Cluj County (Romania), was used to remove heavy-metal ions (Cd2+, Pb2+, Cr3+) from wastewaters. A representative sample of bentonite (P) was characterized using the Brunauer-Emmett-Teller (BET) method, wet chemical analyses, X-ray diffraction (XRD) and Fourier-transform infrared (FTIR) spectroscopy. The bentonite deposit from Petreş ti is present at the contact between Upper Jurassic limestones and basaltic andesites with subordinate basalt bodies. These rocks are composed of clay minerals (mainly smectite), with opal, quartz, feldspar and mica/illite as minor phases. The bentonite sample was used in powdered form (d < 0.2 mm) without any chemical treatment. The influence of the working regime, static and dynamic, on the process efficiency was studied using monocomponent synthetic wastewaters containing Cd, Pb and Cr ions. The bentonite sample proved to be efficient for the removal of these heavy-metal ions; removal efficiencies up to 100% (lead removal) were achieved.

Development of the Polish ceramic industry over the last ten years has resulted in a sharp increase in demand for basic raw materials, especially for ceramic clays – both white- and light-firing as well as red-firing varieties. Polish sources of white-firing clays are rather scarce. Their production is based on Santonian sandy-clayey sediments of the North-Sudetic Trough (Lower Silesia, SW Poland). Light-firing varieties occur mainly in Lower Jurassic sediments on the northern margin of the Holy Cross Mountains (central Poland). Red-firing well-sintering clays of Triassic age are known in the northern margin of the Holy Cross Mountains as well as in the Cracow-Silesian Monocline.

The white-firing Santonian clays contain mainly highly-ordered kaolinite (~50%) and quartz (~30%) with minor amounts of illite. Their grain-size median ranges between 1.9 and 2.5 μm. They show moderate plasticity (bending strength after drying at 1.7–1.9 MPa) and weak sinterability (water absorption after firing ~12%), but greater lightness after firing (L parameter ~86%). The light-firing Jurassic clays are kaolinitic-illitic in character, with a variable content of quartz. Kaolinite is represented by the low-ordered variety. The grain-size median is also variable, ranging between 1.1 and 3.4 μm. They show good plasticity (bending strength after drying 2.6–2.8 MPa), good or very good sinterability (water absorption after firing <6%) but moderate lightness (L ~79%).

Triassic red clays are highly polymineralic, with illite, kaolinite, smectite, chlorite and mixed-layered minerals occurring in variable amounts. Their specific features are: large hematite content (5–12%), commonly small CaO content (<0.5 wt.%) and an extremely small organic matter content (⩽0.1 wt.%). Their grain-size median usually varies between 2 and 3 mm. Using such clays, sintered ceramics (e.g. stoneware tiles) are obtained after firing in the temperature range 1150–1200ºC.

Two kaolins containing kaolinites of different crystallinity, as confirmed by the Aparicio-Galán-Ferrell index, were treated in HCl and KOH solutions at 95º and 80ºC, respectively, for periods up to 36 h. Changes resulting from the treatments have been characterized by several methods. Fe occurs in the octahedral sheets of both kaolinites and dissolves similarly to Al. Lower structural ordering, more structural defects and particles of smaller average size and less regular shape are responsible for faster dissolution of KGa-2 in comparison to well ordered Gold Field (Tanzania) kaolinite. More Si than Al is dissolved in KOH from both kaolins after any dissolution time. An aluminosilicate (feldspathoid) phase is thought to occur in the material prepared from KGa-2 in KOH. Near-IR spectra provide very useful information on changes in the mineral structure upon the treatments, on the solid reaction products and on the adsorbed water molecules.

The main physico-chemical properties of a new smectitic clay containing large amounts of amorphous material are reviewed and potential industrial applications of this type of clay are discussed. Due to a 34% amorphous material content (natural silica gel), the investigated clay has very high porosity and can be used as it is or in acid-impregnated form for oil bleaching or phosphate reduction in edible oil. In the field of biodiesel purification, the new clay can be used to remove, in particular, mono-, diglycerides and glycerol. The natural silica-smectite mixture is also suitable as a carrier for liquid ingredients, for example in animal feeds, and might serve as a partial or complete substitute for synthetic precipitated silicas. In the field of bioseparation processes, the clay can be used as an adsorbent for protein separation by means of cation exchange. Due to the suppressed swelling (compared with smectite alone), it can be packed in columns which can be regenerated.