More than 100 minerals have been reported from the Silver Coin Mine, Nevada USA; five new minerals have been discovered here, due to the unusual geochemical environment. The present study reports on the investigation of a greenish clayey sample from the Silver Coin Mine. After the separation of a fine fraction to enrich the clay minerals, sauconite, a rare Zn-rich smectite, was found by X-ray diffraction (XRD) and was further characterized by differential thermal analysis (DTA), infrared (IR) spectroscopy and scanning electron microscopy (SEM). The Zn-rich smectite is accompanied by illite, minor kaolinite/halloysite and traces of gibbsite (as was indicated by the IR spectroscopy). The occurrence indicates an acidic environment probably caused by oxidation of sulfides.

The determination of the structural formula, to further characterize the Zn-rich smectite, was difficult because of the multi-clay mineral assembly. However, different SEM-EDX (energy dispersive X-ray) approaches as well as transmission electron microscopy (TEM)-EDX analysis helped to characterize the smectite as Al-rich sauconite with some exchangeable K+.

The upper Jequitinhonha Valley is located within the Serra do Espinhaço Meridional mountain range in the State of Minas Gerais, Brazil. The topography is flat or gently undulating with large flat areas known as chapadas (‘high plains’) that are dissected by rivers forming swamps known locally as veredas (‘paths’). The present study is concerned mainly with a representative toposequence in the watershed of the Lagoa do Leandro vereda, a swamp near the city of Minas Novas on a chapada of the highlands of the Alto (Upper) Jequitinhonha region.

The soils of this sequence were studied by a variety of physical and chemical techniques, including Mössbauer, electron spin resonance (ESR) and photoacoustic (PAS) spectroscopies, as well as X-ray diffraction (XRD) and carbon isotope data. Mössbauer spectra of the silt fraction of a grey Xanthic Haplustox (Munsell 10YR 3/2) from the Lagoa do Leandro vereda, referred to here as a ‘Grey Haplustox’ (‘LAC’), proved the existence of Fe2+- and Fe3+-bearing components. Photoacoustic spectroscopy confirmed the presence of Fe2+, as shown by Mössbauer spectroscopy, probably in an octahedrally coordinated site, but the principal optical absorption bands are due to different Fe3+ sites. A ferrimagnetic contribution and three other paramagnetic lines attributed to Fe3+ and Ti3+ were demonstrated by means of ESR. The ESR and PAS results are thus in agreement with the chemical composition and Mössbauer spectroscopy, allowing a detailed characterization of the mineralogy of this silt.

Carbon isotope data indicate the climate to have varied during the past: awetter climate in the Pleistocene, with drier phases in the Late Pleistocene and Holocene, and again a more humid climate 1200 years ago. δ13C data indicate the C3 scrubland vegetation to have occupied the bottom of the vereda in the past (Bispo & Silva, 2014).

Greyish Oxisols that consist chiefly of phyllosilicate minerals of the kaolinite group (which are usually associated with binary oxides and hydroxides) are of common occurrence in tropical soils resulting from leaching and precipitation. Such Oxisols of greyish appearance and similar mineralogy have been described elsewhere from Brazil and, for example, from India. Such soils are therefore proposed here as a new hierarchical level of the Soil Classification System.

Because of widespread tremolite and chrysotile minerals in Palaeozoic-Mesozoic metamorphic and Triassic ophiolitic units, respectively, in the Eskişehir region, Turkey, there is significant potential for development of cases of mesothelioma. Such occurrences in the Eskişehir region show a positive correlation with the concentration and dimension of tremolite crystals compared with those of chrysotile crystals. A detailed assessment of the mineralogy, geochemistry and genesis of these materials has not been carried out to date; the present study was undertaken to fill that gap. The sharp diagnostic basal reflections at 8.14 Å, 3.09 Å and at 7.30 Å, 3.63 Å, well defined fibrous crystallinity, and ideal differential thermal analysis-thermal gravimetric and Raman curves suggest the development of well crystallized fibrous/acicular tremolite and chrysotile with the average structural formulae of: (Na0.07K0.03)(Ca1.68Mg0.18Mn0.01)(Fe0.42Mg4.55Ti0.01)(Si7.60Al0.24Fe0.16)O22(OH)2, and (Mg5.55Fe0.41 Mn0.006)(Si3.79Al0.13)O10(OH)8, respectively.

Enrichment of light rare earth elements relative to medium rare earth elements and heavy rare earth elements in tremolite compared to that of chrysotile which exhibits no anomaly and negative anomalies for Ba, Sr, Ce, Nb, Yand Zr in the tremolite samples and chrysotile, are responses to the fractionation of feldspar, glaucophane, pyroxene and olivine under the high temperatures of hydrothermal-alteration processes during serpentinization and the high-pressure conditions of metamorphism. Based on H and O isotope data, the tremolite and chrysotile are thought to have developed from tectonically controlled magmatic and meteoric hydrothermal systems and the formation temperatures of the tremolite are higher than those of chrysotile.

The Eocene İslambeyli Formation in the Lalapaşa region (NW Thrace, Turkey) consists predominantly of siliciclastic clayey clastics at the bottom and of claystone, tuff and tuffaceous claystone/ sandstone/limestone in the middle and uppermost parts of this formation. Some tuff-tuffaceous beds of the middle–upper parts of the formation are economically viable bentonite depoits. The İslambeyli Formation exhibits vertical variations in the mineralogy, elemental compositions, and smectite-forming processes. Smectite was formed by weathering and diagenetic processes in the fluvial-shore environments in the lower part and by diagenetic alteration in a shallow-marine environment in the middle–upper parts of the formation. Ca-smectite flakes were formed by two processes: direct precipitation; and by means of a dissolution-precipitation mechanism from feldspar and mica. Dissolution-precipitation was most prevalent in the siliciclastic lower part of the formation. The amounts of Al, Fe, Mg and Ca required to form smectite and accessory illite were supplied mainly from the alteration of feldspars, mica and glass shards. The origin of smectite can also be explained by the inferred solution compositions given the parent phases in this formation, and the devitrification of glass shards in pyroclastic-rich middle–upper parts of the formation. In the upper beds, the observed decrease of K and Fe in the smectite structure coincided with both the increase in the amount of smectite and the increase in solution pH suggesting that precipitation of smectite developed over a prolonged period and under arid conditions.

A comparative study using bentonite (BT), hexadecyltrimethylammonium-modified bentonite (BT-HDTMA) and phenyl fatty hydroxamic acid-modified bentonite (BT-PFHA) as adsorbents for the removal of Pb(II) has been proposed. These adsorbents were characterized by X-ray diffraction, X-ray fluorescence, Fourier-transform infrared spectroscopy and surface area measurement. Cation exchange capacity was also determined in this study. The adsorbent capabilities for Pb(II) from aqueous solution were investigated, and the optimal experimental conditions including adsorption time, adsorbent dosage, the initial concentration of Pb(II), pH and temperature that might influence the adsorption performance were also investigated. The experimental equilibrium adsorption data were tested by four widely used two-parameter equations, the Langmuir, Freundlich, Dubinin- Radushkevich (D-R) and Temkin isotherms. The monolayer adsorption capacities of BT, BT-HDTMA and BT-PFHA for Pb(II) were 149.3, 227.3 and 256.4 mg/g, respectively. The experimental kinetic data were analysed by pseudo-first order, pseudo-second order and intraparticle diffusion kinetics models. The experimental data fitted very well with the pseudo-second order kinetic model. Determination of the thermodynamic parameters, ΔG, ΔH and ΔS showed the adsorption to be feasible, spontaneous and exothermic.

This present study provides an overview of the clay-mineral reactions involved in the chloritization process in a mixed-layer mineral series, and focuses on the properties of the resulting lowtemperature chlorites (formed at <220°C) in diagenetic and hydrothermal systems. According to the literature, most chlorite species occurring in low-temperature geological systems are derived fromspecific clay precursors except for direct precipitates from solution in veins. In addition, three main types of clay-mineral series have been associated with these chloritization processes: saponite-to-chlorite, berthierineto- chlorite and kaolinite-to-sudoite reactions. The conversion of saponite to chlorite results in the most common sequence of trioctahedral clay minerals related to the occurrence of Mg-Fe trioctahedral chlorite in a wide variety of hydrothermal and diagenetic to very low-grade metamorphism environments. Two models were proposed in the literature to describe the saponite-to-chlorite conversion through corrensite. The first model is a continuous transition model based on solid-state transformation (SST) mechanisms and is valid in rock-dominated systems (closed micro-systems with very low fluid-rock ratios). The second model is a stepwise transition model based on dissolution-crystallization mechanisms (DC) and is efficient in fluid-dominated systems (open systems with high fluid-rock ratio). The berthierine to Fechlorite transition results in a sequence of trioctahedral phases which are related to chloritization processes in iron-rich and reducing environments. This transformation is a cell-preserved phase transition dominated by a SST mechanismthat operates simultaneously in different domains of the parental mineral and may be considered as a polymorphic mineral reaction. Finally, the conversion of kaolinite to sudoite (Al-Mg ditrioctahedral chlorite) has not been documented like the other two aforementioned conversion series. Despite the scarcity of detailed investigations, the conversion of kaolinite to sudoite through tosudite is considered a stepwise mineral reaction that is dominated by a DC mechanism. From a compilation of literature data, it appears that several parameters of hydrothermal and diagenetic chlorites differ, including the minimal temperature, the textural and structural characteristics and the extents of compositional fields. In hydrothermal systems, discrete chlorite occurs at a minimal temperature near 200°C, regardless of its chemical composition. In diagenetic systems, discrete chlorite occurs at minimal temperatures that vary according to its crystal chemistry (100–120°C for Mg-chlorite as opposed to 40–120°C for Fe chlorite). The strong discrepancy between the lowest temperature at which Mg- and Fe-chlorite form in buried sediments and in geothermal systems should result from drastically different heating rates, heat-flow conditions and tectonism between basins at passivemargins and geothermal systems at active margins. The morphology, structure and compositional fields of the diagenetic Fe-rich chlorite may have been inherited from those of the berthierine precursor. All of the chlorite species formed through theDC mechanism have good geothermometry potential. However, the SST mechanism in which berthierine is transformed into chlorite could have unexplored consequences regarding the use of the chemistry (including stable isotope composition) of diagenetic Fe-chlorite for reconstructing the burial history of sediments. Further investigations regarding the formationmechanisms of mixed-layerminerals are required to provide us with insight to understand the chloritization process in low-temperature geological systems.

Novel composite materials with wide pores were synthesized by an in situ technique using kaolin, palygorskite and pseudoboehmite as raw materials. The characterization results indicated that the synthesis components and conditions influenced the micro-, meso- and macro-porosity of the composite materials. The composites contained 53.5% zeolite Y and had much larger specific surface areas and pore volumes as well as significant hydrothermal stability. Fluid catalytic cracking (FCC) catalysts were prepared based on the composite materials. The results indicated that the as-prepared catalysts possessed a unique pore structure which assisted in diffusion-controlled reactions. In addition, the attrition resistance, activity and hydrothermal stability of the catalyst studied were superior to those of a reference catalyst. The catalyst studied also exhibited excellent nickel and vanadium passivation performance, strong ‘bottoms upgrading’ selectivity and better gasoline and coke selectivity.

Polyamine is a novel inhibitor applied to water-based drilling fluids in order to reduce hydration of clays, especiallymontmorillonite (MT). In the present study, thewater-adsorption properties of montmorillonite intercalated with polyamine were characterized by X-ray diffraction (XRD), diffuse reflectance infrared Fourier transform spectroscopy (DRIFT) and adsorption isotherm tests using water, benzene and heptane. According to the XRD, DRIFT and water-adsorption test results, polyamine (PA)- intercalated montmorillonite (PA-MT) adsorbs less water than either K+- or NH+4-intercalated montmorillonite (K-MT, NH4-MT). The surface energy of MT was analysed using the van Oss- Chaudhury-Good (VCG) approach based on thewater, benzene and heptane adsorption results. The surface energy between PA-MTand water was less than that of NH4-MT and K-MT. Compared with K-MT and NH4-MT, the surface energy of the Lewis acid portion of PA-MT underwent a more significant decrease, suggesting that the hydration of unexchanged Na+ did not make a discernible contribution. The experimental water-adsorption data were fitted using Langmuir, Brunauer-Emmett-Teller (BET), and Freundlich adsorption models. The Langmuir adsorption models can be used to fit the data for water adsorption on PA-MTacross the entire p/p0 range. After plotting the experimental data in the linear format of the Freundlichmodel, only one linear region for PA-MTwas observed, indicating a singlewater-adsorption mechanism for PA-MT. When compared with PA in the absence of clay, DRIFT spectroscopy showed that the NH2 bending mode for PA-MT shifted from 1571 cm–1 to 1619.7 cm–1. This suggested an increase in hydrogen bonding (H bonding) between the ammonium group and the interlayer water. Across the entire p/p0 range, water is suggested to have adsorbed onto PA-MT through H-bonding interactions between the ammonium group and the interlayer water.