bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pedogenic Formation of Montmorillonite from a 2:1-2:2 Intergrade Clay Mineral
Authors: Malcolm R. L. , Nettleton W. D. , McCracken R. J. 
Published: August 2006

AbstractMontmorillonite was found to be the dominant clay mineral in surface horizons of certain soils of the North Carolina Coastal Plain whereas a 2:1–2:2 intergrade clay mineral was dominant in subjacent horizons. In all soils where this clay mineral sequence was found, the surface horizon was low in pH (below 4·5) and high in organic matter content. In contrast, data from studies of other soils of this region (Weed and Nelson, 1962) show that: (1) montmorillonite occurs infrequently; (2) maximum accumulation of the 2:1–2:2 intergrade normally occurs in the surface horizon and decreases with depth in the profile; (3) organic matter contents are low; and (4) pH values are only moderately acid (pH 5–6).It is theorized that the montmorillonite in the surface horizon of the soils studied originated by pedogenic weathering of the 2:1–2:2 intergrade clay mineral. The combined effects of low pH (below 4·5) and high organic matter content in surface horizons are believed to be the agents responsible for this mineral transformation. The protonation and solubilization (reverse of hydrolysis) of Al-polymers in the interlayer of expansible clay minerals will occur at or below pH 4·5 depending on the charge and steric effects of the interlayer. A low pH alone may cause this solubilization and thus mineral transformation, but in the soils studied the organic matter is believed to facilitate and accelerage the transformation. The intermediates of organic matter decomposition provide an acid environment, a source of protons, and a source of watersoluble mobile organic substances (principally fulvic acids) which have the ability to complex the solubilized aluminum and move it down the profile. This continuous removal of solubilized aluminum would provide for a favorable gradient for aluminum solubilization.The drainage class or position in a catena is believed to be less important than the chemical factors in formation of montmorillonite from 2:1–2:2 intergrade, because montmorillonite is present in all drainage classes if the surface horizon is low in pH and high in organic matter.
Properties of Vermiculites and Smectites: Expansion and Collapse
Authors: Harward M. E. , Carstea D. D. , Sayegh A. H. 
Published: August 2006

AbstractSamples of smectites and vermiculites were evaluated to (1) determine the effects of source and amount of charge, (2) determine if a continuum of properties exists, and (3) improve the basis for differentiating criteria for identification.The montmorillonites expanded to the equivalent two-layer complex upon solvation by condensation of ethylene glycol or glycerol vapor. Beidellite exhibited the one-layer complex with glycerol vapor and the two-layer complex with ethylene glycol. The vermiculite samples did not yield regular two-layer complexes regardless of saturating cation, prior moisture or solvating agent. A number of different complexes of vermiculite were obtained depending on conditions of solvation. These corresponded to spacings of approx 13·6, 14·0, 14·3, 15·0, and 15·3 Å. Two or more of the complexes may be present in the same sample.Potassium-saturated vermiculites and smectites both exhibited collapsed layers in a dry atmosphere. Hydration of smectites occurred at humidities above 20 per cent and resulted in poorly ordered diffraction maxima of 11–12 Å. The K-saturated vermiculites tended to retain the collapsed lattice and exhibited diffraction maxima of 10–10·6 Å with integral higher orders. Some hydration occurred as evidenced by peak asymmetry or the appearance of a small 14·3 Å line at higher humidities, although the collapsed spacing predominated. The tendency of vermiculite to hydrate decreased as the exchange capacity increased.Differences in properties can be related to both source and amount of charge. Nevertheless, a continuum in the properties of expansion and collapse between the smectites and vermiculites was not observed. The data indicate two discrete populations. These properties may be used as differentiating criteria for identification.
Cation Replacement Studies on Heteroionic Bentonitic Clay Fractions Using Specific Ion Glass Electrodes
Authors: Fertl Walter , Jessen F. W. 
Published: August 2006

AbstractCentrifuged fractions, ranging in size from 2·0 to 0·05 μ of a Wyoming bentonite, Bentonita de Durango from Mexico, and Helms clay from Texas were studied. The variation in replacement of Na+, Ca2+, Mg2+, K+, and H+ from these heteroionic clay systems under specific equilibrium conditions of salt concentrations was measured.The displacement cation distribution was monitored by using specific ion glass electrodes, such as a sodium ion electrode, a cationic glass electrode, a calcium ion electrode and a Tektite electrode. Some factors affecting the exchange reactions are discussed and application of findings to drilling and production techniques is indicated.
Formation of Halloysite from Feldspar: Low Temperature, Artificial Weathering Versus Natural Weathering
Authors: Parham Walter E. 
Published: August 2006

AbstractWeathering products formed on surfaces of both potassium and plagioclase feldspar (An70), which were continuously leached in a Soxhlet extraction apparatus for 140 days with 7·21 of distilled water per day at a temperature of approximately 78°C, are morphologically identical to natural products developed on potassium feldspars weathered under conditions of good drainage in the humid tropics. The new products, which first appear as tiny bumps on the feldspar surface, start to develop mainly at exposed edges but also at apparently random sites on flat cleavage surfaces. As weathering continues, the bumps grow outward from the feldspar surface to form tapered projections, which then develop into wide-based thin films or sheets. The thin sheets of many projections merge laterally to form one continuous flame-shaped sheet. The sheets formed on potassium feldspars may then roll to form tubes that are inclined at a high angle to the feldspar surface. Etch pits of triangular outline on the artificially weathered potassium feldspars serve as sites for development of continuous, non-rolled, hollow tubes. It is inferred from its morphology that this weathering product is halloysite or its primitive form. The product of naturally weathered potassium feldspars is halloysite · 4H2O.The flame-shaped films or sheets formed on artificially weathered plagioclase feldspar do not develop into hollow tubes, but instead give rise to a platy mineral that is most probably boehmite. These plates form within the flame-shaped films, and with continued weathering are released as the film deteriorates. There is no indication from this experiment that platy pseudohexagonal kaolinite forms from any of these minerals under the initial stage of weathering.
Potassium Release from Muscovite as Influenced by Particle Size
Authors: von Reichenbach H. Graf , Rich C. I. 
Published: August 2006

AbstractCompleteness of exchange of K from muscovite by Ba2+ ions decreased with particle size below 20 μ. Accompanying K exchange at 120°C, using a repeated batch technique, was a marked loss of Si and the formation of boehmite in the finer fractions. Several possible explanations for the unexpected high K retention of fine mica fractions are discussed. The formation of a diffusion-inhibiting surface “skin” is discounted, because equilibrium was obtained more rapidly with the fine fractions than with coarser fractions. The average degree of bending of unit mica layers due to peripheral expansion is probably greater in large particles. With bending, rotation of tetrahedra and shifting of adjacent layers with respect to each other may induce greater release of K and a lower selectivity for this ion. Fault planes may induce preferential expansion of individual layers and initiate interstratification and splitting of particles. Splitting of particles may reduce bending and increase K selectivity.
Electron Microscopic Identification of Single Crystals of Wairakite, a Rare Component in Clays
Authors: Kiss Klara , Page Harold T. 
Published: August 2006

AbstractCrystallites of the finest fraction of a clay mineral from Rosamund, California, which account for over 50 per cent of the total weight, are identified as wairakite single crystals of 0·1–1 μ size. High-magnification electron microscopy revealed flat, almost perfectly square-shaped lamellae, which consist of superimposed layers of approximately < 50 Å thickness. Electron diffraction patterns from a selected single crystal proved that the basal plane of the crystallite aligned perpendicular to the electron beam is the (111) plane. It is suggested on the basis of the present study and the report of previous investigators that the pseudocubic wairakite crystals cleave along their (111) and ($\bar 1$11) planes. The indices of high order reflections, unpublished or previously reported as uncertain, are determined.
A Method for Removing Titanium Dioxide Impurities from Kaolin
Authors: Maynard R. N. , Millman N. , Iannicelli J. 
Published: August 2006

AbstractThe removal of titanium minerals from kaolin can be accomplished by treatment with dispersing agents in an amount in excess of that required to produce maximum deflocculation of the kaolinite particles. In this reflocculated state the kaolinite particles attain a high degree of suspensional stability, and the titanium mineral particles, primarily anatase, are liberated and can be separated by sedimentation. Substantial removal of anatase impurities can be achieved by this method.
Interparticle Potential Energies in Na-Montmorillonite Clay Suspensions
Authors: Taylor T. R. , Schmidt P. W. 
Published: August 2006

AbstractThe small angle X-ray scattering data obtained in an earlier investigation of a series of Na-montmorillonite clay samples containing varying concentrations of sodium metaphosphate have been used to calculate the potential energy φ(x) of the interaction between two isolated parallel clay platelets separated by a distance x. All φ(x) curves have the form expected for Na-montmorillonite. In each curve there is a potential well for a platelet separation approximately equal to the most probable separation distance determined in the earlier study. Because the depth of the potential well is of the order of 0·01 eV for all samples, the attractive forces are relatively weak. While the calculated φ(x) functions are not highly accurate, in future investigations precautions can be taken to increase the reliability of the computed potential energy functions. This preliminary study suggests that determination of φ(x) from small angle X-ray scattering data can be a useful method for quantitative study of interparticle forces in Na-montmorillonite clays.
Rheological Model Studies in Clay
Authors: Christensen R. W. , Kim J. S. 
Published: August 2006

AbstractThe 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.
Specific Co-Absorption of Purines and Pyrimidines by Montmorillonite (Clay-Organic Studies XV)
Authors: Lailach G. E. , Brindley G. W. 
Published: August 2006

AbstractThe co-absorptions of various purines and pyrimidines from aqueous solutions by Na- and Ca-montmorillonite are studied in the range of pH 1–6. The pyrimidines, thymine and uracil, which are not absorbed from solutions of these Compounds alone, are appreciably absorbed from solutions containing also adenine or 2,6-diaminopurine, are weakly absorbed from solutions containing hypo-xanthine, and are not absorbed from solutions containing purine, cytosine, and caffeine. The specific co-absorption is tentatively attributed to hydrogen-bond formation between the molecules in solution rather than to an overlapping of the molecular configurations (vertical stacking). The montmorillonite-organic associations have a basal spacing of about 12-5 Å which permits only a single molecular layer between successive silicate layers.
Lithium and Potassium Absorption, Dehydroxylation Temperature, and Structural Water Content of Aluminous Smectites
Authors: Schultz Leonard G. 
Published: August 2006

AbstractX-ray analysis of Li+- and K+-saturated samples, differential thermal analysis (DTA), thermal gravimetric analysis (TGA), and chemical analysis of 83 samples enable a distinction to be made between Wyoming, Tatatilla, Otay, Chambers, and non-ideal types of montmorillonite, and between ideal and non-ideal types of beidellite. The Greene-Kelly Li+-test differentiates between the montmorillonites and beidellites. Re-expansion with ethylene glycol after K+-saturation and heating at 300°C depends upon total net layer charge and not upon location of the charge. Wyoming-type montmorillonites characteristically have low net layer charge and re-expand to 17 Å, whereas most other montmorillonites and beidellites have a higher net layer charge and re-expand to less than 17 Å.Major differences in dehydroxylation temperatures cannot be related consistently to the amount of Al3+-for-Si1+ substitution, nor to the amount of Mg, Fe, type of interlayer cations, or particle size. The major factor controlling temperature of dehydroxylation seems to be the amount of structural (OH). Of 19 samples analyzed by TGA, montmorillonites and the one ideal beidellite that give dehydroxylation endotherms on their DTA curves between 650° and 760°C all contain nearly the ideal amount of 4(OH) per unit cell, but the non-ideal montmorillonites and beidellites that give dehydroxylation peaks between 550° and 600°C do not. Non-ideal beidellites contain more than the ideal amount of structural (OH) and non-ideal montmorillonites seem to contain less, although the low temperature of dehydroxylation of the latter could also be due to other structural defects. Change in X-ray diffraction intensity of the 001 reflection during dehydroxylation suggests that the extra (OH) of beidellite occurs at the apex of SiO4 or AlO4 tetrahedrons with the H+ of the (OH)− polarized toward vacant cation sites in the octahedral sheet.
Soil Minerals in the Al2O3-SiO2-H2O System and a Theory of Their Formation
Authors: Kittrick J. A. 
Published: August 2006

AbstractAn attempt has been made to assemble the best thermodynamic information currently available for soil minerals in the Al2O3-SiO2-H2O system at 25°C and 1 atm. Montmorillonite is included by considering its aluminum silicate phase. Diagrams are presented so that the stability of the minerals can be visualized in relation to the ionic environment. Although the Al2O3-SiO2-H2O system is a very simple one compared to soils and sediments, the stability diagrams depict a mineral stability sequence and mineral pair associations that are in good agreement with natural relations.According to the stability diagram, mineral pairs that can form in intimate association are gibbsite-kaolinite, kaolinite-montmorillonite, and montmorillonite-amorphous silica. Forbidden pairs are amorphous silica-kaolinite, amorphous silica-gibbsite, and montmorillonite-gibbsite. The formation of intimate mixtures of three or more of these minerals is also forbidden. The stability diagrams predict ion activity relationships that are in reasonable agreement with those obtained from soils and sediments.Amorphous silica probably limits high silica levels, with montmorillonite also forming at high silica levels. Kaolinite forms at intermediate and gibbsite at low silica levels. These minerals in turn probably control the activity of aluminum ions at a level appropriate to the pH. The formation of gibbsite, kaolinite, montmorillonite and amorphous silica appears to be controlled by a combination of kinetics and equilibria. That is, the kinetic dissolution of unstable silicates appears to control the H4SiO4 level. The new mineral(s) most stable at that H4SiO4 level appear to precipitate in response to solution equilibria.
Refinement of the Crystal Structure of Nacrite
Authors: Blount Alice M. , Threadgold I. M. , Bailey S. W. 
Published: August 2006

AbstractThe crystal structure of nacrite from Pike’s Peak district, Colorado, has been refined by least squares and electron density difference maps utilizing ten levels of data. Complete refinement was inhibited by thick domains involving a/3 interlayer shifts in the “wrong direction”. The ideal structure is based on a 6R stacking sequence of kaolin layers, in which each successive layer is shifted relative to the layer below by −1/3 of the 8·9 Å lateral repeat. This direction is X in nacrite, contrary to the usual convention for layer silicates, because of the positioning of the (010) symmetry planes normal to the 5·1 Å repeat direction. Alternate layers are also rotated by 180°. The pattern of vacant octahedral sites reduces the symmetry to Cc and permits description of the structure as a 2-layer form with an inclined Z axis.Adjacent tetrahedra are twisted by 7·3° in opposite directions so that the basal oxygens approach more closely both the Al cations in the same layer and the surface hydroxyls of the layer below. Interlocking corrugations in the oxygen and hydroxyl surfaces of adjacent layers run alternately parallel to the [110] and [11̄0] zones in successive layers. The upper and lower anion triads in each Al-octahedron are rotated by 5·4° and 7·0° in opposite directions as a result of shared edge shortening. Nacrite has a greater interlayer separation and smaller lateral dimensions than dickite and kaolinite, and the observed β angle deviates by 1½° from the ideal value. These features, as well as its overall lesser stability, are believed due to the less favorable positioning in nacrite of the basal oxygens relative to the directed interlayer hydrogen bonds.
Montmorillonite-Organic Complexes - Gas Chromatographic Determination of Energies of Interactions
Authors: Bissada K. K. , Johns W. D. 
Published: August 2006

AbstractGas-solid chromatographic measurements of interaction energies were made for the systems ethanol and acetone with K-, Na-, Ba-, and Ca-montmorillonites. The results revealed an increased interaction energy in the orderK-mont. < Na-mont. < Ba-mont. < Ca-mont.Interaction energies ranged from about 14 kcal/mole for K-montmorillonite to about 30 kcal/mole for Ca-montmorillonite. A very good agreement was observed between experimental heats of adsorption values and theoretical values for the electrostatic attractive energy between the respective cations and polar molecules.These results confirm our earlier suggestions that complex formation takes place through cation-dipole interactions and that the polar molecules solvate the exchange cations in a manner similar to the hydration of cations in aqueous solutions.
Surface Conductance and Electrokinetic Properties of Kaolinite Beds
Authors: Lorenz Philip B. 
Published: August 2006

AbstractA technique was developed for forming clay beds of uniform porosity between 48 and 62 per cent. The surface conductance and streaming potential of sodium kaolinite were determined over a range of values. Zeta potential as calculated from the classical formula was about - 30 mV at neutral pH and changed sign at pH 4. The surface conductivity of the sodium clay at various pH values was directly proportional to the zeta potential and from 12 to more than 30 times as large as the calculated electrokinetic surface conductivity. Similar measurements were made on kaolinite in the acid (hydrogen-aluminum) and calcium forms. The acid clay fitted the experimental correlation found for the sodium series, but the calcium clay, with less than one-tenth of the zeta potential of the sodium clay at neutral pH, had half its surface conductance. The results are interpreted as showing that exchangeable ions on kaolinite are mostly in a condensed layer on the surface where the mobility determines surface conductance. The surface mobilities for Na, Ca and H-Al are 20, 8 and 0 per cent of normal, respectively. Apparently hydrogen ion from the solution is very effective in replacing sodium, which exhibits its electrokinetic and conductive properties in proportion to its concentration on the surface.
Transformation of Montmorillonite to Nickel-Chlorite
Authors: Gupta G. C. , Malik W. U. 
Published: August 2006

AbstractNickel-chlorite has been obtained by the co-precipitation of nickelous hydrous oxide and montmorillonite at an OH/Ni ratio of 2.0. Chemical analysis shows that 16 me of Ni is fixed per gram of clay. System without any free nickelous hydrous oxide is quite stable up to an investigated period of 6 months, shows impedence to collapse on heating to 550°C, and no expansion of 001 spacing on glycerol treatment.Different properties studied (X-ray diffraction analysis, thermal [D.T.A. and T.G.A.] data, i.r. absorption analysis, Polarographic reduction behavior and cation exchange capacity measurements) confirm the complete transformation of montmorillonite to nickel-chlorite.“Seeding” of the hydroxide out of the “fixed” interlayer positions takes place on ageing the sample with free nickelous hydrous oxide. No montmorillonite could be detected by X-ray diffraction analysis in spite of this backward reaction.
Anauxite and Kaolinite Structures Identical
Authors: Bailey S. W. , Langston R. B. 
Published: August 2006

AbstractSingle crystal X-ray diffraction patterns reveal that the structure of selected anauxite crystals is the same as the structure of macroscopic kaolinite crystals. Anauxite and kaolinite crystals are intergrowths on a domain scale of units in pseudotwin orientations. Individual domains in anauxite have the triclinic geometry of kaolinite, and give X-ray reflections that compare closely in intensity with those calculated from the atomic parameters of kaolinite. Large crushed crystals of anauxite give powder patterns identical with that of kaolinite. Because it has been shown recently that the chemical composition of anauxite is also identical with that of kaolinite, it is recommended that the term “anauxite” no longer be used.
A Purple-Colored 1M Mica Clay From Silverton, Colorado
Authors: Tien Pei-Lin 
Published: August 2006

AbstractA purple-colored clay of 1M mica polymorph in association with lead-zinc ore was collected from an abandoned mine dump near Silverton. Colorado. Electron micrographs show that the crystallites of the clay are less than 2μ in size and have poorly developed hexagonal outlines. Differential thermal and i.r. absorption analyses indicate similarity with those of muscovite. The structural formula of the 1M mica polymorph is (K1.45 Na0.02) (Al3.75 Mg0.19) (Si6.90 Al1·10) O20 (OH)4. The purple color may be related to trace amounts of manganese in the clay.