On the Helen claim in Homansville Canyon, East Tintic district, a small deposit of kaolinic clay typical of argillic alteration, together with hematite and manganese, occurs at the intersection of a minor north-south fissure with a steep east-trending contact of Tertiary quartz latite lava and dolomitized Cambrian Herkimer limestone. The fissure ends at a small, completely argillized monzonite plug about 100 yd north.

Argillic alteration and other types of hydrothermal alteration are common near the ore deposits and many of the intrusive bodies that are scattered through the roots of the Eocene volcanic field in which the East Tintic and Tintic districts lie. In most areas of argillic alteration abundant pyrite or alunite and barite suggest that the alteration was caused largely or in part by sulfur acids, but in the Helen claim these minerals are virtually lacking and in contrast fluorite, hematite, and manganese and aluminum oxides are abundant.

A mineral zonation parallel to the lava-dolomite contact is conspicuous. The zones in the lava outward from the contact are: (L 1) a silicic zone 1–5 in. wide with some kaolinic clays, mixed-layer clay and micaceous minerals; (L 2) a strongly argillized zone about 3 ft wide having much montmorillonite and a moderate amount of kaolinic and micaceous minerals, but in which the kaolinic minerals decrease away from zone L 1; (L 3) transition zone 2–5 ft wide in which montmorillonite diminishes, micaceous minerals increase, and kaolinic minerals disappear as altered rock grades into normal country rock. The bulk density of the rock decreases with the intensity of argillic alteration and nearly all chemical constituents decrease in amount per unit volume; magnesium, water, manganese, and fluorine, however, increase conspicuously.

The zones in the altered dolomite away from the lava contact are (D 1) a hematite-quartz zone 5–8 ft wide, which contains some minor sericite and manganese oxides; (D 2) a manganiferous zone 1–2 ft thick containing abundant manganese oxides and hematite, and minor clay, quartz, and kaolinic minerals; (D 3) a discontinuous zone about 8 in. thick of halloysite and kaolinite; (D 4) a fluorite–kaolin zone with minor diaspore about 1 ft thick; (D 5) a diaspor-fluorite zone about 41/2 ft wide in which the kaolin minerals diminish away from zone D 4; (D 6) a diaspore–kaolinite zone about I ft wide with minor fluorite and mixed-layer clays; (D 5) a kaolin and mixed-layer clay zone about 3 in. thick with very minor manganese oxide, fluorite, and diaspore; (D 8) a “sanded dolomite” zone about 10 ft wide, consisting chiefly of weakly bonded granular dolomite with some kaolinite and mica; (D 9) hard fresh hydrothermal dolomite extending outward for several hundred feet. Zone D 8 grades imperceptibly into D 9.

The mineral zones suggest reaction of dolomite with hot halogen-rich acid emanations carrying halides of iron, aluminum, and silicon; the precipitation of the oxides of iron, manganese, silicon, and aluminum, and of fluorite, is appropriate to zonation responsive to the increasing pH caused by reaction with the carbonate wall rock.

This paper presents data on clay-size material in the loess of southwestern Iowa. Most of the loess samples studied are Wisconsin in age. Regional distribution of clay-size material in the loess is discussed, and data are given on the modes of occurrence of clay in the loess. The following test methods were used to study the clay fractions of selected loess samples: Mechanical analysis, differential thermal analysis, cation-exchange determinations, refractive index determinations, and x-ray diffraction techniques. These tests indicate a uniformity in clay-mineral composition, with montmorillonite and illite group minerals predominating. Clay contents from mechanical analysis are correlated with various properties of the loess; in most cases the properties appear to be linear functions of the clay content. The plastic limit is discussed in detail.

The direct application of heavy metal- and quaternary ammonium-based antibacterial agents can cause inconvenience such as irritation, short-term applicability, discoloration of the tissue, and environmental concerns. The immobilization of these agents on montmorillonite (Mnt) was expected to diminish these effects by hindering direct contact of the ions with the target tissues. The objective of the present study was, therefore, to prepare inorgano(I)- and organo(O)-montmorillonites (I/O-Mnt) and to determine their potential uses in such biomedical applications. Na-montmorillonite (Mnt-Na) was modified by hydrothermal and microwave irradiation methods using Cu2+/Zn2+, and quaternary ammonium and/or anionic surfactants. The effect of the structures formed by immobilization on Mnt surfaces on antibacterial activity was investigated. Quaternary ammonium surfactants were cetyltrimethyl ammonium bromide (CTAB) with a linear alkyl chain, cetylpyridinium chloride (CPC) with a single aromatic ring, and benzethonium chloride (BZT) with double aromatic rings. N-lauroyl sarcosinate (SR) was the anionic surfactant. The samples were subjected to thermogravimetric (TGA) and scanning electron microscopy (SEM) analyses. Desorption tests showed that the antibacterial efficacy against Streptococcus mutans stemmed from I/O-Mnt and not from the ions released from the material surfaces to the aqueous phase. The results of the antibacterial studies showed that the existence of a linear alkyl chain and a double aromatic ring were the structural factors causing the greatest antibacterial effect. The time-kill tests revealed that Mnt-CTA, Mnt-BZT, and Mnt-CP-SR were effective against Streptococcus mutans within 5 min of contact. With the new findings, they were identified as possible selective and potent bactericidal agents and promising candidates for biomedical applications.

Regolith-hosted rare earth element (REE) deposits hosted by the granitic regolith in South China provide >90% of the world’s heavy REEs. Kaolinite is one of the major carriers of REE ions in regolith. The formation and transformation of kaolinite can be affected by chemical weathering and hydrodynamic conditions, but the contribution of each factor has not been evaluated. This study systematically investigated the variation in abundance of phyllosilicate minerals and structural order of kaolinite in the Renju regolith-hosted REE deposit. The total abundance of 1:1 phyllosilicate minerals increased upwards along the profile from Section I to Section III. However, semi-quantitative analyses indicated that Section III-1 (depth at 10–16 m) featured an evident decrease in both abundance and structural order of kaolinite upward along the profile. The morphological feature and abundance of kaolinite revealed intensive kaolinite-to-halloysite transformation and kaolinite dissolution in Section III-1. This suggests that the alternating wetting and drying zone in Section III-1 provided a favorable kinetic environment for the entry of water molecules into the kaolinite interlayer and the kaolinite-to-halloysite transformation, resulting in both lower structural order and abundance of kaolinite in Section III-1. Moreover, REE ions started to be enriched from the alternating wetting and drying zone and formed high-grade ores at the lower part of the water table, due to a significant increase in pore water and decrease in the seepage velocity. Therefore, the abundance and structural order of secondary kaolinite can serve as important indicators of hydrodynamic changes in regolith, as well as the mineralization of regolith-hosted REEs.

To identify the mechanisms for and to estimate the photochemical reaction efficiency of molecules in solid-state host materials is difficult. The objective of the present research was to measure the photogeneration efficiency of the methylviologen cation radical (MV+•) hosted in a semi-transparent hybrid film composed of MV2+ and saponite, a 2:1 clay mineral. MV+• is the one-electron reduced species of MV2+. MV+• was generated by UV irradiation of these films. The fluorescence intensity of MV2+ and the photogeneration efficiency of MV+• depended on the loading level of MV2+. When the loading level of MV2+ was high (75% of the cation exchange capacity (abbreviated as % CEC) of saponite), its fluorescence was reduced considerably because of the self-fluorescence quenching reaction, and the photogeneration efficiency of MV+• was relatively high (quantum yield φ = 3.5×10–2) compared to that of films with low adsorption density (10% CEC, φ = 1.1×10–2). Furthermore, when the loading level of MV2+ was very low (0.13% CEC), a self-fluorescence quenching reaction was not observed and MV+• was not generated. From these observations, one of the principal mechanisms of the self-quenching reaction and MV+• formation in saponite is the electron transfer reaction between excited MV2+ and adjacent MV2+ molecules in the ground state.

In a hitherto unpublished manuscript dated 1794–95, H.-B. de Saussure described three types of rudimentary laboratory experiments on weathering, each one lasting about 4 hours, undertaken on samples of jade, serpentine, feldspar, and mica schist. He submitted these samples to dry heating, heating with continuous addition of water, and heating with periodic addition of water. Experimentation was performed at temperatures of the order of 200–250°C, and Saussure seems to have realized that a reasonable increase of temperature was necessary for laboratory simulation of long-lasting geological processes. No changes were observed during dry heating whereas increasing alteration was noticed in the presence of water, particularly when heating was combined with periodic wetting. He concluded that these tests demonstrated his preconceived idea that weathering of minerals (mostly silicates) resulted from alternating periods of drying and wetting. This concept is basically very close, if not identical, to that underlying modern ideas on seasonal weathering.

Direct analysis by Fourier transform methods revealed interstratification of three components for a homogeneous, potassium-treated and organic-solvated montmorillon-ite. An initial simple interpretation based on random mixing of two components was shown to be incorrect. Ethylene glycol solvation showed enhanced expansion in agreement with earlier investigations. Glycerol solvation produced a noteworthy contribution from a 14 Å component. An interpretation of the 14 Å component is suggested, based on an asymmetric distribution of layer charge. Regular interstratification, bending or curling of clay layers and anomalous dehydroxylation temperatures may be a consequence of asymmetric layer charge distribution in montmorillonites.

Kaolinite originating by the low-temperature subaerial transformation of montmoril-lonite occurs extensively in Tertiary clayey sands of central and northern Florida. It occurs in gray iron-stained weathering zones, as much as several feet thick, that transgress primary green clays of the Bone Valley and other formations over hundreds of square miles. Subjacent deposits of opal and chert, clearly post-depositional, are a widespread byproduct of the transformation.

Kaolinization begins as a hexagonal modification of the edges of montmorillonite flakes. X-ray study reveals that montmorillonite degrades and disappears up-section, with the appearance of the 7.2 kaolinite reflection and a very small 20–21 Å reflection. The altered clay loses silica and gains alumina and water.

The clay transformation apparently proceeds by intracrystalline leaching of tetrahedral silica layers by slightly acid ground water. Approximately regular interposition of resultant stripped packets within montmorillonite creates a regular 1:1 mixed-layered montmorillonite-kaolinite, which responds as montmorillonite does to glycolation and heating. The stripped kaoline-like packets develop hexagonal outgrowths of true kaolinite by lateral epitaxy. Nourished by the decomposing montmorillonite, the outgrowths enlarge and nucleate new vertical growth, observed as oriented crystallites, 40–50 Å thick.

Transformation of montmorillonite to kaolinite is a major geochemical process: creating goethite-stained kaolinitic sands of regional extent, liberating much silica for chert deposition and ground-water enrichment, and constituting an eluvial process that leads, in some areas, to residual quartz sand plains.

Variations in the peptization resistance of selected samples of clay mineralogical materials toward alkaline dispersing agents are discussed from a quantitative point of view.

Clay samples, collected from South Carolina, Wyoming, Illinois, New Mexico, South Wales, Great Britain and Cornwall, England were subjected to the action of solutions of Calgon (“sodium hexametaphosphate”), ammonia, sodium hydroxide, sodium carbonate, sodium pyrophosphate, and “sodium lignosulfonate.” The resulting apparent dispersion, in each case, was expressed as a function of the employed concentration and chemical nature of the dispersing agent. Pipette analysis and Oden balance techniques at constant temperature were used to measure the degree of dispersion. All clay samples employed were identified as to type by X-ray diffraction, chemical analysis, thermal analysis, and electron microscopy.

All samples examined exhibited a maximum in apparent dispersion (suspension stability) at a specific concentration of dispersing agent. Such maximum was followed by a sudden decrease in apparent dispersion, i.e., flocculation, at higher concentrations of dispersing agent. Concentrations of dispersing agent were varied in steps of one part per thousand. One hundred and twenty experimental runs were made on each type of material examined. Differences in the degree of apparent dispersion attained by use of different dispersing agents were expressed in terms of a threshold concentration which altered “equivalent diameter” one tenth of a phi unit. Among dispersing agents employed, “sodium lignosulfonate” was found to be least selective of clay mineral type in its peptizing action.

An equation for the calculation of a “peptization resistance factor” is presented. Results obtained by application of this equation indicate that differences in the response of the same clay material to different alkaline dispersing agents may be attributed, in part, to differences in degree of peptization achieved by “threshold mechanisms” of peptization and by “adjustment mechanisms” along the peptization path. Such equation may have future value in the differentiation of marine and terrestrial clay deposits.

Control of the structure and morphology of clay crystals presents a challenge in the synthesis of materials for adsorption and catalysis. In the present study, direct crystallization of a phyllosilicate grafted with organosilyl (methylsilyl and phenylsilyl) groups on the surface of monodisperse spherical silica particles (2.6 μm) is reported. Methyl- and phenyltriethoxysilanes were allowed to react hydrothermally in a Teflon-lined autoclave with silica, MgCl2, and LiF in the presence of urea for 2 or 4 days. X-ray diffraction patterns revealed that the fine platy particles formed were a trioctahedral hectorite-like layered silicate. Greater temperature (150°C) was required to achieve homogeneous coverage of the original spherical silica particles with the hectorite-like particles. The diameter of the initial silica grains increased slightly to 3.0 μm after the hydrothermal reactions, while the original spherical shape and size distribution were maintained. Solid-state 29Si nuclear magnetic resonance analyses confirmed that the presence of resonances attributed to the RSi(OMg)(OSi)2 and RSi(OMg)(OH)(OSi) (R = methyl or phenyl) environments of the silicon proved the formation of covalent bonds between phyllosilicate sheets and the organic moieties. The crystallinity of the layered silicates increased when the reactions ran for a longer time (4 days).

Shales of marine, brackish-water, and nonmarine origin, collected from cyclothems of Pennsylvanian age, were analyzed chemically and mineralogically. Clay mineral identifications were accomplished using x-ray diffraction and differential thermal analysis techniques. Summations of the structure amplitudes of the individual clay minerals formed a basis for semi-quantitative ratios between illite and kaolinite-chlorite. Illite was found to be enriched in the marine shales. The origin of the authigenic clay minerals in the shales is discussed from two aspects. The first and probably the more correct uses the thesis that the ultimate clay mineral is built up from a skeletal aluminum-silicate structure; the second discusses the origin of the clay minerals from a purely colloidal point of view. Trace element determinations, pH values, and pipette analyses are also included as a part of this study.

Desorption processes of low-molecular-weight compounds from the surface of smectites into the gas phase determine a number of processes, e.g. those involved in drug delivery and the release of herbicides. The desorption has not been investigated thoroughly and is not well understood. The present study was undertaken in order to understand better the factors influencing these desorption mechanisms. Starting with a very pure standard (Na+-rich) montmorillonite (Kunipia-F), which was exchanged against cations with different hydration properties (Ca2+, Li+, phenyltrimethylammonium, hexyltrimethyl-ammonium), the experiments explored the rate of desorption of volatiles with different chemical functionalities (water, ethanol, ethyl acetate, and toluene). The desorption was monitored by thermogravimetry and differential scanning calorimetry under isothermal conditions, and by ramping the temperature at a constant rate. The experiments were compared with numerical calculations based on finite-element methods and with analytical models. These data point to a two-step mechanism where the desorption follows the curve of the equilibrium desorption isotherms of those molecules on the montmorillonite. The bulk-like volatiles (i.e. volatiles with release kinetics close to that of the bulk liquids) were desorbed in a first step. With a decrease in the degree of coverage of the volatile on the montmorillonite, the desorption was increasingly dominated by the strength of interaction between the volatile and the interlayer cations of the montmorillonite.

Lubricants are an essential component in high-performance mechanical equipment, but traditional lubricants are becoming inadequate for meeting the increasing demands for anti-friction and anti-wear properties and they discharge harmful chemicals to the environment. The purpose of the present study was to explore the use of sepiolite as a novel oil additive to extend the performance of lubricants. Sepiolite nanofibers were first treated by acid followed by a dry air flow, aimed at increasing the pore volume and decreasing the particle size. Then the nanofibers were further modified by an organosilane coupling agent to reduce the surface free energy and to improve the dispersion stability in lubricant. A significant improvement in the performance of the lubricant was achieved by using the modified sepiolite nanofibers as an additive. When the amount of modified sepiolite nanofibers added was 1.5 wt.%, the best performance was demonstrated by the lubricant, showing a viscosity increase at 40°C and 100°C, and an increase in resistance to oxidation. Moreover, the acid value and pour point decreased, and the copper sheet corrosion level dropped to its lowest value.

The exclusion of anions relative to tritiated water from the negatively charged interlamellar spacing of hydrobiotites that have a limited degree of lattice expansion permits measurement of the interlamellar volume. Measurement of the changes in the interlamellar volume and in the exchange capacity, when hydrobiotite lattices are collapsed by potassium treatment or expanded by treatment with sodium tetraphenyl boron, provides a means for estimating the distribution of the surface charge densities of these interstratified minerals.

In the hydrobiotite sample studied (Zonolite from Traveler’s Rest, South Carolina), the biotite fraction was estimated to have a surface charge density of 2.0 ± 0.14 × 10−7 meq cm−2 and the vermiculite fraction, 1.5 ± 0.51 × 10−7 meq cm−2. The charge density, and its relative distribution, was reflected in the tendency of these mineral fractions to collapse upon potassium treatment and to entrap trace concentrations of cesium in the interlayer spacing.

Scanning electron microscopic (SEM) examination of the quartz isolated from chert of Transvaal and Swaziland, of 2000 and 3400 million year (MY) ages, respectively, in southern Africa revealed marked differences in quartz morphology. Well-defined individual euhedral quartz crystals, with polyhedral triple-point faces, were clearly evident on freshly fractured Transvaal chert surfaces as well as with the quartz isolates from the chert. The morphology and coarseness suggest crystal growth with little, if any, metamorphism; however, the δ18O values of 23.8–24.1‰ suggest crystallization temperatures of perhaps 40–45°C. In contrast, fracture surfaces of the older, strongly metamorphosed Swaziland cherts revealed a high degree of grain intergrowth which inhibited fracture between quartz grains. Quartz isolates from these showed strongly interlocked quartz crystal clusters and elongated chips of quartz with poorly defined irregular faces. Intercalation of mineral veins in the cherts on a mm scale and the intergrown character of the quartz grain boundaries provide evidence that the latter cherts have been strongly metamorphosed and recrystallized, in keeping with 14.6–15.1‰ δ18O values, corresponding to 80°C fractionation with water. The SEM micrographs of the fine quartz (1–10 µm) isolated from the Otavi dolomite formation of the 700-MY Damara System and from the 2000-MY Transvaal Dolomite Series revealed well-defined subhedral and euhedral quartz crystals of small size which, together with the 26.9–27.8‰ and 23.8‰ δ18O values, respectively, indicate that these dolomites have been affected little, if any, by post-depositional metamorphism; their crystallization temperatures fall in the range of 25–30 and 40–45°C, respectively.

A Vermiculite from Beni-Uxera, North Africa, was refluxed with HC1 solutions of various concentrations to determine the effect of such a treatment on its surface area. The treated vermiculite was analyzed for “free” SiO2 and by x-ray diffraction, and the refluxing solutions were analyzed for the cations removed from the vermiculite. Surface areas were determined by means of adsorption isotherms of n-butane at 0°C.

The surface area of the acid-treated vermiculite increases with increase in concentration of the acid. Heating of the acid-treated samples or the natural samples decreases the surface area.

The increase in surface area by acid treatment is due to destruction of the vermiculite and its conversion to a “free” form of SiO2 which possesses a large surface area. x-Ray analysis indicated that this “free” SiO2 was not present in the interlayer positions of the crystal lattice of vermiculite.