A standardless method of energy dispersive X-ray fluorescence in conjunction with scanning electron microscopy was used to analyze selected areas of clay-size particles of talc, pyrophyllite, and kaolinite supported by a carbon planchet. Peak intensity ratios of fluorescing elements relative to silicon were converted directly to weight or mole ratios using conversion factors determined theoretically. The conversion factors depend upon particle thickness and mass adsorption coefficients of the sample for the elements analyzed. The effects of particle thickness become significant above ~0.1 μm. Without using particle thickness corrections, the mean molar ratios of metal to Si agreed to within 6.1,0.5, and 9.7% of the theoretical ratios for kaolinite, pyrophyllite, and talc, respectively.

Although several hypotheses for the formation of glauconite have been proposed, the sedimentary environment and mechanism of glauconitization are still poorly understood. In this contribution, the mineralogy and chemical compositions of sediments from Paleogene formations (Fms) in the Kyzyltokoy basin (Kyrgyzstan) were examined to better understand glauconitization processes. The samples were analyzed using microscopic petrography, X-ray diffraction (XRD), electron probe microanalysis (EPMA), and X-ray fluorescence (XRF). Interlayered diatomite-argillaceous rocks were newly identified within the diatomites of the Isfara Fm. Glauconite from the Kyzyltokoy basin displayed two stages of maturity: 1) early stage (nascent) glauconite grains composed of ∼3.5% K2O and ~8% FeOT; 2) late-stage (highly evolved) glauconite grains composed of 7–9% K2O and ~27% FeOT. The early stage glauconite grains in the Hanabad Fm green clay (green clay is clay with a greenish color) indicate interruptions in glauconitization processes, whereas the (highly) evolved glauconite grains show a completed glauconitization process along the contact between the Hanabad and Sumsar Fms. Hematite was detected in the red clay (clay with reddish color) of the Sumsar Fm and probably formed by glauconite disintegration. Accordingly, the Paleogene Fms depositional conditions were of three types: 1) beginning of glauconitization with interruptions, 2) completion of glauconitization, and 3) glauconite disintegration. Glauconitization in the Kyzyltokoy basin, thus, likely occurred via a combination of dissolution, precipitation, and recrystallization processes.

The process of deformation in clays is visualized as the combination of recoverable deformation resulting from bending and rotation of individual particles and irrecoverable deformation due to relative movement between adjacent particles at their points of contact. The relative movement between particles is treated as a rate process in which interparticle bonds are continually broken and reformed as the deformation proceeds. Accordingly, the rate of deformation is governed by the activation energy associated with the rupture of interparticle bonds. Thus, in terms of a rheological model, the fundamental element consists of a spring, representing the recoverable deformation, in series with a rate process dashpot representing the irrecoverable deformation.

Owing to the heterogeneous nature of the fabric of clay soils, i.e. varying particle size, shape, orientation, surface characteristics, etc., a wide range of activation energies, elastic stiffness, and other material properties is anticipated. This is accounted for by assuming a Gaussian distribution for the model properties. Thus, the complete rheological model postulated in this study consists of a combination of spring and dashpot elements covering the complete spectrum of model properties.

The response of the rheological model is analyzed for creep and constant strain-rate loading. The analysis is accomplished numerically using a digital computer since no closed form solution exists for the non-linear systems of equations that result from this model. Experimental data for a number of triaxial tests on clays under various conditions of loading are presented for comparison with the model behavior.

In this paper we analyzed by electron microscopy and X-ray diffraction (XRD) the exposed lacustrine clay in a stratigraphic column at Charo Canyon, State of Michoacán, Mexico. Smectite, cris-tobalite, albite and quartz are the main mineral species in the sediments. Smectite is the most abundant and has a nanometric twinned small particle habit. The low crystallinity of the smectite detected in some of the samples seems to be associated with instability of the paleohydrological regime in which clayey material was deposited. Iron from underlying volcanic ash is apparently responsible for the iron concentration detected in the smectite structure.

X-ray, chemical, and genetic characteristics of a chloritized montmorillonite mineral species, found in The Río Chiflón Formation (La Torre, La Rioja, Argentina) are described. The mineral is associated with illite, montmorillonite, and chlorite, plus the non-clay associates analcite and hematite. The Río Chiflón Formation is of Upper Triassic age, and consists of red sandstones and siltstones representing poorly developed fluviatile cyclothems.

Studies of the Li+, K+ and Mg2+ varieties of the clay, and solvation with glycerol or ethylene glycol have shown that the mineral is a smectite which behaves peculiarly with heating. Between 200° and 600°C the mineral collapses gradually from a basal spacing of 13–10 Å. Regular expansibility with ethylene glycol and glycerol is completely preserved (in the Li+ and K+ clays) up to a preheating of 400°C and partially preserved up to 600°C. This behavior has been interpreted as caused by the presence of interlayer contaminants of a hydroxy-cation type. The interlayer cations may be Al, Mg, and Fe, (in this order).

The environment of the Río Chiflón Formation has been evaluated in the light of well-known occurrences of intergradient clays in soils, and the presence of analcite and hematite. It is proposed that chloritization has taken place during a soil weathering process, under alkaline conditions with great availability of sodium during alternating dry-humid seasonal climates (oxidation conditions). The stability of the interlayer developed under these circumstances was increased during long burial and diagenesis.

Eocene-aged bentonite deposits in Gonzalez (Texas, USA) carrfy scattered manganese oxide-rich pods where rare earth element (REE) concentrations as high as 7800 ppm have been detected — 10 times greater than in the already enriched bentonite. This study investigated the nature of the association between REEs and Mn oxides as well as REE modes of occurrence in these pods, in order to understand the processes that mobilize and accumulate REEs in the low-temperature depositional environment of the Texas coastal plain. Embedded, polished blocks of Mn pods were analyzed by Scanning Electron Microscopy (SEM); sections were then extracted by the FIB liftout technique from regions bearing REEs for further analysis by Transmission Electron Microscopy (TEM). The SEM and TEM results revealed the presence of abundant yttrium phosphate nanoparticles identified as xenotime, forming large globular aggregates that reach a few microns in diameter; these xenotime aggregates also host trace concentrations of Zr, Dy, Er, Yb, and Ce. Further, rhabdophane nanoparticles were detected that host predominantly light REEs and Y. The relative proportions of REEs in rhabdophane vary between particles and show decoupling of Ce from other light REEs, suggesting oxidation from Ce3+ to Ce4+. The REE enrichment of these Mn pods is due to extensive weathering along fractures cutting through the bentonite deposit that drove their remobilization and transport downward. At the base of the bentonite, where fractures terminate against the boundary with a cemented sandstone, changes in flow regime combined with gradual downward changes in fluid composition, prompted co-precipitation of Mn oxides and REE phosphates (xenotime and rhabdophane).

The Dolná Ves K-bentonite deposit is one of a few known economic accumulations of illite-smectite in the world. Several studies have been done on the illite-smectitic component isolated from the Dolná Ves K-bentonite, but there is a shortage of analytical data on the K-bentonite itself. The main goal of the present study was to perform mineralogical and physico-chemical characterizations of various technological types of K-bentonites from the Dolná Ves deposit to better understand the relationships between the various qualitative types and their properties. The type I (high-grade) K-bentonite contains 88–91 wt.% of illite-smectite. The type II (low-grade) K-bentonite contained substantially less illite-smectite, ranging from 37 to 63 wt.%. The illite-smectites isolated from the type I K-bentonites displayed greater expandability, contained more octahedral Mg and less octahedral Fe, had greater cation exchange capacity (CEC), smaller thickness of fundamental particles, and thinner illite-smectite crystals in comparison with illite-smectites from the type II K-bentonites. The LOI (loss-on-ignition) and Al2O3 content increased with increasing amount of illite-smectite. The increase in the expandability by 10% corresponded to an increase in CEC by ~10 meq/100 g. The type I K-bentonites had much greater mass loss at <250°C due to greater expandability. The best tilemaking performance was expected for the type I K-bentonite. This raw material could also be potentially valuable for the pharmaceutical, cosmetic and food industries. Overall, the results showed that the studied technological types of K-bentonites from the Dolná Ves deposit differ not only in terms of illite-smectite contents but also in terms of the nature of the illite-smectites.

A method using the bombardment of samples with protons and other positive ions of energy in the MeV range is described: the prompt atomic (γ-rays) and nuclear (γ-rays and charged particles) events generated during the bombardment, are detected with energy sensitive solid state detectors: cooled Ge(Li) for γ-rays and hard γ-rays, cooled Si(Li) detectors for soft γ-rays (3–20 keV) and Si-barrier detectors for charged particles. These 3 types of detectors can be simultaneously used for multipurpose experiments. These techniques are particularly useful for simultaneous detection of all the elements of interest in the sample. Comparisons are made with other microtechniques. Analyses of Li, Na, K, Ca, Rb, Cs and Cl exchanged in appropriate chloride solutions have been achieved for several clays (Geisenheim, Isola di Ponza, Layton). A new phenomenon relative to the anion contribution in cation exchangers is observed. A method of profile analysis of Na by resonant nuclear reactions is discussed.

Interparticle friction is the principal property which permits soils and granular materials to resist load without formation. Dry soils of virtually all types are highly stable. The suitability of soils for engineering purposes depends largely upon their ability to remain in place and support whatever loads may be placed upon them, either by a permanent engineering structure or by transient vehicle loads. A study of the properties which distinguish the more satisfactory from the less satisfactory soils indicates that in the majority of eases clays are detrimental to stability. It is apparent that wet clay has the effect of a lubricant in diminishing the natural resistance due to friction that would otherwise exist. It is necessary that the civil engineer responsible for construction of any form of earth work should be informed not only concerning the Quantity of clay minerals that are present but also about their nature and their potential influence on the engineering properties of the soil.

Factors controlling the crystal structure of phlogopite have been widely investigated; but the role of electrostatic interactions, for example, has received much less attention than other factors. The purpose of the present study was to peform a single-crystal refinement of an Al-saturated phlogopite and to use that refinement to supplement crystal-chemical analyses. The phlogopite investigated was from the Rumford quadrangle, Maine, and has the following chemistry: ${\left({\text{K}}_{0.81}{\text{Na}}_{0.03}\right)}_{\Sigma =0.84}{\left({\text{Mg}}_{1.84}{\text{Fe}}_{0.52}^{2+}{\text{Al}}_{0.45}{\text{Mn}}_{0.02}{\text{Ti}}_{0.07}^{4+}\right)}_{\Sigma =2.90}{\left({\text{Si}}_{2.78}{\text{Al}}_{1.22}\right)}_{\Sigma =4}{\text{O}}_{10}{\left({\text{OH}}_{1.81},{\text{F}}_{0.05}\right)}_{\Sigma =1.86}$\$\end{document}. The sample is a 1M polytype with C2/m symmetry and cell dimensions of a = 5.3220(4), b = 9.2170(7), c = 10.2511(8) Å, and β = 100.081(1)°. Hydrogen atoms were located and the crystal structure was refined to give parameters R1 = 0.0301 and weighted R2 = 0.0887. The octahedral M1 site was larger than the M2 (average M1—O: 2.079 Å, average M2—O: 2.062 Å) and the electron counts were equal (M1 = M2 = 14.8 e−); based on bond distances, which are more accurate than electron counts in determining occupancy; this result is consistent with a slight preference of Mg for M2 and Fe2+ for M1.

Thirty-five Al-rich, natural phlogopite-1M samples that are of (1) high metamorphic grade, and that have (2) total Al contents ⩾ 1.27 atoms per formula unit (a.p.f.u.), (3) Fe3+ contents ⩽ 0.11 a.p.f.u., and (4) Mn contents ⩽0.10 a.p.f.u. along with the newly described phlogopite, exhibited crystal chemical trends related to increasing Al content. Octahedral substitutions of smaller, high-charge cations (i.e. Al) apparently decrease distortions in the octahedral sites and produce longer M2—O4 distances. In addition, VIFe-F avoidance apparently occurs in high Al-content samples, which are generally high in VIFe. The data set also shows that these samples have limited ordering among M sites (Fe2+ in M1 and Al in M2), an increase in β (99.96° to 100.32°) possibly caused by cation ordering and therefore size differences of M1 and M2, and interlayer (A) sites with A—Oouter distances that increase and A—Oinner distances that decrease with increasing Ti content.

Computer models were used to simulate electrostatic interactions in phlogopite structures with variable Al concentrations utilizing Pauling’s electrostatic valency principle, which considers first-coordination electrostatic interactions. The model results were compared to the maximum Al concentrations in natural and synthetic phlogopite samples. Model results revealed no indications (e.g. a limit reached or a sudden change occurred) that charge saturation/undersaturation of the apical oxygen atoms at Al contents equal to the maximum in natural and/or synthetic samples causes instability that could not be balanced by bond-length variation. However, a cation of higher charge substituting at M1 (or M2) may result in higher electrostatic repulsions between the other octahedral sites. Thus, the Al3+ content in the octahedral sites may reach a maximum, with Fe2+ for Mg substitutions favored.

Refractory clay, derived from hornblende chlorite schist that was hydrothermally altered along nearly vertical fractures and faults, occurs near Guanajuato, Mexico, a few kilometers south and east of the famous monument, El Cristo Rey. Part of the chlorite is expanding, i.e. probably mixed-layer vermiculitic chlorite or biotite. The most refractory clay is comprised chiefly of kaolinite, with variable amounts of finely crystalline quartz. Huge, thick “gossans” of silica have been deposited as surface-covers over the fractures; such silica gossans are fairly common over Mexican hydrothermal clay deposits and may be used as probable field guides to argillation.

The trend of mineralogical and chemical changes (analyses tabulated in the paper) during argillation of the Guanajuato material is traced in overlapping sequence, as follows:

1. (a) bleaching of green ferro-ferric silicates accompanied by oxidation of part of the iron to “limonite”.

2. (b) leaching of alkali and alkaline earths accompanied by

3. (c) partial desilication of parent silicate minerals yielding kaolinite whose flakes are commonly oriented parallel with the chlorite of the schist, mobile silica, and finely divided quartz intermixed with the kaolinite

4. (d) refinement (“purification”) of the clay by further kaolinization and removal of silica minerals and some iron oxide.

The final clay may run higher in silica than does its parent rock.

Clay minerals are common constituents of the Miocene Surma Group reservoir rocks in the Sylhet Trough, Bengal Basin, and may exert significant controls on reservoir quality. The relationship between diagenetic clay minerals and reservoir quality in the petroliferous Sylhet Trough is poorly understood, however. The current study was aimed at the origin and diagenetic pattern of clay minerals in interbedded sandstones and shales using thin-section petrography, scanning electron microscopy (SEM), and X-ray diffraction (XRD), and understanding their diagenetic effects on reservoir quality. The results showed that the clay mineral cements in sandstones comprise mainly chlorite, illite/illite-smectite, and minor smectite and kaolinite. In the early diagenetic stage, clay rims and growth of vermiform kaolinite occur and partly occlude the pore throats. Deep burial effects include pore-filling, pore-lining, and grain-coating authigenic clays (mainly chlorite and illite). Diagenetic clay minerals and mechanical clay infiltration showed a systematic distribution in sandstones lying in the vicinity of sequence and parasequence boundaries. In a lowstand systems tract (LST), clay minerals within the sandstones commonly include mechanically infiltrated smectitic clays that eventually evolved to grain-coating chlorite and/or illite during the meso-diagenesis stage. The presence of clays/clay minerals has no significant impact upon reservoir quality of sandstones. The Surma Group shales are enriched in illite with significant proportions of chlorite and kaolinite and are likely to be mainly detrital, with diagenetic changes of smectite to illite.

Aluminum substitution is a common phenomenon in environmental iron oxides and oxyhydroxides, affecting the color, magnetic character, surface features, etc. Several methods for preparing Al-substituted iron oxyhydroxides can be found in the literature, resulting in samples with particular properties. In the present study, the synthesis of aluminum-substituted goethites, AlxFe1-xOOH with 0 ⩽ x ⩽ 0.15, by homogeneous precipitation and the transformation to aluminum-substituted hematites, (AlxFe1-x)O3, are presented. The goethite samples were produced at 90°C from solutions of urea and iron and aluminum nitrates in the presence of ammonium sulfate (GU series). Although attempts were made to incorporate up to 33 mole% of Al into the goethite, only ~15 mole% was found to be within the structure, due to the final pH, ~7, of the synthesis. Another feature of these goethites was a lateral alignment of the tabular particles. By heating batches of the GU samples at 400°C and 800°C, two series of Al-hematites were obtained, denoted here as the HX400 and HX800 samples, respectively. X-ray diffraction, thermal analysis, Karl-Fischer titration, transmission electron microscopy, and Mössbauer spectroscopy were used to characterize the samples. The X-ray patterns showed the samples to be pure iron phases, with particle sizes of ~10 nm for the GU and HX400 samples, and of ~70 nm for the HX800 samples. An inversion in the intensities of the (104) and (110) diffraction peaks of hematite was observed to be dependent on the aluminum substitution and was explained by small particle sizes, shape anisotropy, and the presence of nanopores. The cell parameters of both GU and HX samples showed a small decrease with increasing aluminum substitution up to x ≈ 0.15. The amount of adsorbed sulfate, presumably as an aluminum hydroxy sulfate gel, increased with aluminum substitution in all GU and HX samples, reaching a maximum of ~6.5 wt.% for the highest substitution. Heating at 100°C did not remove all of the adsorbed water, and significantly higher temperatures were required to achieve complete removal. Mossbauer spectra at 295 K and 80 K are typical for small-particle goethite and hematite, and revealed that Al-for-Fe substitution in all samples seems to be limited to ~15 mol.%.

Chlorites formed as a replacement of phenocrysts in metabasites from the pumpellyite-actinolite to lower-greenschist facies Mikabu and North Chichibu belts in southwest Japan were studied by X-ray powder diffraction, electron microprobe analysis (EMPA) and high-resolution transmission electron microscopy (HRTEM). The metabasites contain a small quantity of fine-grained smectite and corrensite in the <1 μm size fraction. The chlorite also contains trace amounts of Ca, Na and K, which generally appear to be associated with smectite stacked in chlorite packets. The smectite layers comprise up to 13% of the chlorite domains. Theoretical estimates of the smectite ratio by the Wise method using EMPA data coincide well with the ratio determined based on HRTEM observations in most chlorites. However, in some chlorites with high proportions of Ca, Na and K, the cations cannot be reasonably attributed to smectite alone. Based on the present analyses, Ca, Na and K cations are also hosted in discrete interstitial phases of fine-grained smectite and corrensite as possible retrograde metamorphic products. These findings suggest that care should be taken in application of the Wise method to estimate the smectite ratio, and that the whole-rock chlorite composition may not be suitable as a geothermometer.

Acid-base titrations and attenuated total reflectance-infrared (ATR-IR) spectroscopy of solutions containing Zn(NO3)2 and the herbicide 3-amino-1,2,4-triazole suggested that soluble complexes ZnL2+ and Zn(OH)L+ form, where L represents aminotriazole. Sorption experiments and modeling in systems containing K-saturated Wyoming (SWy-K) montmorillonite suggest that at low concentrations the aminotriazole sorbs primarily in cationic form via an ion-exchange mechanism. Sorption isotherms for aminotriazole are ‘s’-shaped, indicating a co-operative sorption mechanism as the concentration of the molecule increases. At higher concentrations, ATR-IR spectroscopy indicated the presence of cationic and neutral triazole molecules on the surface, while X-ray diffraction data suggest interaction with interlayer regions of the clay. When the concentration of the herbicide was high, initial sorption of aminotriazole cations modified the clay to make the partitioning of neutral molecules to the surface more favorable. Experiments conducted in the presence of Zn(II) indicated that below pH 7, Zn(II) and aminotriazole compete for sorption sites, while above pH 7 the presence of Zn(II) enhances the uptake of aminotriazole. The enhancement was attributed to the formation of an inner-sphere ternary surface complex at hydroxyl sites (SOH) on crystal edges, having the form [(SOZn(OH)L)]0.

The nature and morphology of Al(OH)3 polymorphs obtained by precipitating Al and tartrate at pH 12.0 and at a tartrate/Al molar ratio (R) of 0.1 were studied by X-ray diffraction, transmission electron microscopy and electron diffraction. Co-crystallization of unusually long (up to 18 µm) ‘stick-shaped’ gibbsite with platy particles of both nordstrandite, mainly, and bayerite was observed. Face-to-face associations of plates nucleated perpendicularly on the gibbsite surfaces parallel to the c axis produced peculiar elongated ‘brush’ -shaped particles. In a strongly alkaline environment the inhibiting effect of tartrate on Al(OH)3 polymorph formation is reduced and production of co-crystallized phases with structural crystallographic similarities can be observed.

Rectorites containing various amounts of Ca were found at the Sano Mine, Nagano Prefecture, Japan. The Ca content in nonexchangeable form varied from 1.0 to 3.9% CaO. With more than 3.4%, they may be called Ca-rectorite. Chemical data of the most Ca-rich sample showed that Ca was the dominant interlayer cation, and gave a structural formula of (Mg0.16)EX(Ca0.59Na0.27K0.17)FIX[Al3.94Mg0.08 Fe0.07Ti0.01](Si5.85Al2.15)O20(OH)4. This sample is apparently the most Ca-rich rectorite reported to date. The Greene-Kelly test and an intercalation examination by octadecylammonium indicated that the expandable component layers were beidellitic. Assuming the tetrahedral composition of the expandable component layers are similar to the average tetrahedral composition of beidellite of (Si3.6Al0.4), the tetrahedral composition of the mica-like component layers was calculated to be (Si2.25Al1.75). This was closer to a brittle mica (margarite) than to a true mica. Examination of chemical data for several Ca-rectorite samples from different localities, including those from the Sano Mine, showed a trend of increasing Ca content as Al increased and Si decreased. Ca-rectorite exhibited characteristic infrared absorption bands at 480, 670–700 and 900–930 cm−1, which became more intense as Ca content increased. These bands also corresponded to major absorption bands of margarite.

The reactions between montmorillonite and carbonates and hydroxides of Na, K and Li were studied at 550°C as a function of salt content and time. The reactions were found to be rapid with a half-time of 20–30 minutes. Good agreement was obtained between theoretical and experimental stoichiometric values for the clay-carbonate reaction. The 001 and 02,11 reflections of the products of the clay-salt reactions diminished in intensity and/or disappeared at and above the stoichiometric concentrations of the reactants.