The evolution of clay minerals in a Navarre Andosol (Spain) is investigated. The results indicate formation of allophane, evolution of trioctahedral mica to dioctahedral illite and the appearance of 10:14 A interstratified mineral in the lower layer. In the top horizons the interstratified mineral changes into vermiculite. The mineral distribution in the profile is indicated.

The experimental data on adsorption of Fe and CN of a ferrocyanide complex onto raw and acid-activated clinoptilolite/sepiolite on the basis of detention time and particle size was modelled by a linear and a non-linear approach. The linearized best-fit isotherm selection method and non-linear error minimization was applied through Freundlich, Langmuir and Temkin isotherms. ERRSQ, MPSD, HYBRID and ARE error functions were minimized by a developed MATLAB script to determine the isotherm parameters in non-linear optimization. The complex was not adsorbed as whole anions but the Fe and CN were adsorbed separately. 0.65 mg Fe/L. min and 4.84 mg CN/L. min initial adsorption rates were achieved with acid activated clinoptilolite. The Fe adsorption was not as successful as CN. The adsorption of Fe and CN was described by Freundlich and Langmuir isotherms respectively. The differences between the predicted isotherm parameter sets of linear models and minimized error function models indicated that both the best-fit isotherm selection and the isotherm constant determinations can be performed properly by error minimization as well as by conventional linear best fit modelling approach.

The mineralogical composition, microfabrics and geochemistry of a set of eight samples derived from a narrow area of NE Peloponnese (Greece), where engineering works are presently in progress, were investigated in this study. No important mineralogical differences were observed between the samples other than a variation in the proportions of the participating phases. Analyses reveal that these sediments consist mainly of carbonates (calcite, dolomite), quartz and feldspars (albite, orthoclase). Carbonate minerals exhibit a micritic texture and a high degree of cementation bonding. Phyllosilicates and clay minerals are also common, with smectite and mixed-layer smectite-chlorite being the prevailing phases, followed by chlorite and white mica (muscovite, illite). According to the physical properties measured on bulk samples, the samples were found to exhibit a low to medium expansion, low to intermediate plasticity, normal activity and brittle behaviour. The porosity does not exceed 46% and the organic matter ranges between 3.80 and 5.00%. The high degree of cementation, the dispersed appearance of clays, the small pores (<10 μm) and the common occurrence of smectite in a mixed-layer with chlorite are all favourable characteristics, positively influencing the sediment's stability for engineering constructions.

La formación Fardes consiste en secuencias alternadas de turbiditas y hemipelagitas. Estos sedimentos han sido silicificados diagenéticamente y se presentan como estratos gruesos de color amarillo, que contienen jarosita y sideronatrita, inicialmente depositados en un medio reductor. Los niveles hemipelagíticos se pueden considerar por su composición quimica y mineralógica como bentonitas, compuestas principalmente de esmectitas, mica y cuarzo. En algunos casos se han encontrado asimismo, calcita, dolomita, halita y yeso. En la fracción <2 µm el mineral más abundante es la esmectita (48%) seguido por la palygorskita y la mica (28% y 32% respectivamente). La composición de la esmectita corresponde a los miembros ricos en Fe de la serie nontronita-beidellita; las micas son verdaderas moscovitas y la paligorskita tiene contenidos anormalmente altos de Fe y Al. Evidencias mineralógicas y geoquimicas indican que estas bentonitas son productos de alteración de rocas volcánicas, posiblemente, andesitas calcoalcalinas.

A method of adapting a 9·0 cm X-ray camera is described

A focusing X-ray powder camera is described in which the degree of focusing varies with 2θ and can be made a maximum for any one reflection. It is of simple design and has two main uses:—(a) for a routine identification of the main clay mineral groups by their basal reflections, and (b) for the detection of very small amounts of any one crystalline component in a mixture.

This paper presents the results of acidic leaching of kaolinite from the flotation waste of the RTB Bor copper mine, Serbia. The kaolinitic concentrate from the flotation waste contains 32% Al2O3. Kinetic investigations were conducted on the leaching of kaolinite roasted at 750°C for 60 min under air using H2SO4, HNO3 and HCl. Activation energies for the process were 74, 63 and 63.2 kJ mol–1 for sulphuric, nitric and hydrochloric acids, respectively. The kinetic function D3: [1 – (1 – α)1/3]2 = kt was chosen to describe the fractional conversion dependence on time and temperature. This enabled effective management of the leaching process to be carried out.

When studying surface free energies of clays in relation to clay composition, we calculated that in some instances the aggregate stability should be higher for Na- then for Ca-forms. This raised the question as to whether the results obtained with the surface free energy approach are reliable for estimation of soil aggregate stability. The aim of the present work was to measure the surface free energy components and attractive forces for a clay calculated from measurements of the contact angle of glycerol, diiodomethane and cis-decalin and to compare them with results of penetrometrical measurements.

This study reports a leaching process along with a novel physical pretreatment technique to remove iron impurities from kaolin using oxalic acid. A detailed examination of the physical properties of the minerals confirmed that almost none of the leaching-resistant iron oxides, specifically hematite, was completely interlocked with the clay minerals. Accordingly, a pre-agitating technique followed by high-pressure washing of the sample on a 600 μm sieve were applied. In this method, by discarding up to 20% of the raw material, >54% of the total iron content of the raw kaolin was removed, and the iron content was reduced from 9.75% in the initial sample to <6.00% in the passing fraction. Application of this pretreatment method rendered the leaching process successful at 97°C using 0.3 M oxalic acid solutions for 1 h under atmospheric pressure. Compared to the leaching of the raw material without pretreatment, which consumed at least 0.5 M oxalic acid over a minimum period of 2 h, the method used was very cost-effective and favourable, reducing the iron content of the product to <1% and producing high-quality kaolin.

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.