bluuebunny/crossref_metadata_2025_split huggingface dataset:
Redox Behaviour of Iron in Hydroxylated Silicates
Authors: Addison W. E. , Sharp J. H. 
Published: August 2006

AbstractThe oxidation and reduction of clay minerals, particularly chamosite and nontronite, are compared with those of the amphibole crocidolite. Oxidation is very similar, but differences in behaviour on reduction are described. These differences are interpreted in terms of the different environments of the oxygen atoms in the various structures. Mechanisms of the various processes are discussed in detail.
Montmorillonite-Polyalcohol Complexes: Part II
Authors: Brunton George , Tettenhorst Rodney , Beck Carl W. 
Published: August 2006

AbstractOscillating-heating X-ray diffraction was used to determine d-spacings and intensity changes of the (001) diffraction maximum for various combinations of 3 clays, 6 cations and 7 polyalcohols from 20°C to 1000°C under non-equilibrium conditions.The temperature of collapse of the one layer complex was measured. Analysis of variance of this parameter for a model containing 3 clays, 6 cations and 7 polyalcohols showed that there is a significant difference among cations and polyalcohols but not among clays.Additional work on one clay, 6 cations and 18 polyalcohols shows that ΔT—the difference in temperature between the collapse of the clay-organic complex and the boiling point of the polyalcohol—is proportional to the length of the carbon chain ; ΔT is also a function of the number and position of the OH groups.The mean temperatures of final collapse for all polyalcohols are related to the valence of the interlayer cations and inversely related to their ionic radii.There are two groups of d-spacings for the one-layer complexes. Complexes with polyalcohols having OH groups at the ends of the chain have mean d-spacings between 13.6–13.7 Å, while complexes with polyalcohols with interior OH groups have mean d-spacings of 13.9–14.0 Å.
Hydrothermal Rhyolitic Alteration in the Castle Mountains, California
Authors: Heystek Hendrik 
Published: August 2006

AbstractX-ray diffraction, differential thermal, chemical analysis and cation exchange data indicate a progressive genesis upon hydrothermal alteration of rhyolitic materials in an extensive fault zone. Kaolinite, a Ca-Mg beidellite, mixed-layer beidellite-hydrous mica and beidellite-vermiculite clay minerals, quartz, cristobalite and feldspar commonly occur in the deposit.Detailed studies show that the sequence of the 2:1 clay mineral alteration is beidellite-hydrous mica mixed-layer → beidellite-vermiculite mixed-layer → beidellite. This mineralogical change parallels a progressive decrease in the layer charge and amount of fixed K+ present and an increase in exchangeable Ca+ and Mg+ respectively.
Stevensite and Talc—Hydrothermal Alteration Products of Wollastonite
Authors: DeRudder Ronald D. , Beck Carl W. 
Published: August 2006

AbstractMagnesium-bearing hydrothermal solutions moving along channelways created by faulting in the Willsboro, New York, wollastonite deposit have effected the conversion of wollastonite to layer-lattice silicates. Alteration products sheath faults in wollastonite and may be divided into three gradational but regular zones: (1) least altered (fresh) country rock composed of wollastonite with minor diopsidic clinopyroxene and grossularite-andradite garnet; (2) moderately altered rock rich in montmorillonite; and (3) strongly altered rock composed predominantly of talc.X-ray diffraction, oscillating-heating X-ray diffraction, electron microscopy, infrared absorption, base exchange, and chemical analyses substantiate identification of the montmorillonitic alteration product, pseudomorphous after wollastonite, as stevensite. Stevensite, a trioctahedral magnesium montmorillonite, has been reported heretofore only in basaltic rocks where it has been formed by the action of magnesium-bearing solutions on pectolite. Pectolite and wollastonite have similar compositions and structures and may be similarly converted to stevensite in a magnesium-rich hydrothermal environment.Talc, the dominant mineral in the most intensely altered zone bordering the solution channelway, was formed by the continuing action of magnesium-bearing solutions on stevensite. Stevensite has a defect structure, i.e., a deficiency in the total number of ions in octahedral coordination. The addition of magnesium from hydrothermal solutions to the octahedral layer of stevensite converts this mineral to talc, concomitantly freeing interlayer cations and water.Stevensite is unstable and is converted to talc above a temperature of 275°C at water pressures of 690 bars. It is believed that hydrothermal alteration of wollastonite took place at temperatures near or below 275°C with stevensite forming in the cooler part of the reaction zone, and talc forming from stevensite at slightly higher temperatures nearer the solution channelway.
Variability in “crystallinity” Values among the Kaolin Deposits of the Coastal Plain of Georgia and South Carolina
Authors: Hinckley David N. 
Published: August 2006

AbstractQuantitative measurement of the relative degree of crystal perfection among 144 samples of Coastal Plain kaolin shows that the deposits are nonhomogeneous with respect to crystallinity and that the hard and soft types can be distinguished at the 0.95 probability level by an analysis of variance. The nonhomogeneity of the deposits and the distinction between the hard and soft types agrees with the results obtained for other properties not reported here. Although on the basis of pulverizing ease there may be a single population with hard and soft end members, in terms of origin the evidence indicates the existence of two distinct clay populations.
Clay Mineral Effects on the Stress-Strain Response of Soils in Direct Shear
Authors: Kondner Robert L. , Vendrell José R. 
Published: August 2006

AbstractMore than one hundred sets of direct shear tests were conducted on soils composed of four reference clay minerals and various combinations of the four clay minerals of the Columbia University Clay Mineral Standards Project (A.P.I. 49) to illustrate with quantitative results the influence of clay mineralogy on the stress-strain characteristics of soils and hence the practical importance of clay mineralogy in soil mechanics. The soils tested consisted of various amounts by weight of Bedford Indiana Halloysite, Mesa Alta New Mexico Kaolinite, Santa Rita New Mexico Montmorillonite and Fithian Illinois Illite prepared with distilled water. The experimental results agree quite well with hyperbolic stress-strain relations previously developed by the author. The Hvorslev strength parameters are written as exponential functions of the clay mineral content and are included in the hyperbolic stress-strain law. The ultimate shear strength of the soils are mathematically expressed in terms of the stress history, confinement, and mineralogy.
Swelling Pressures of Sodium Montmorillonite at Depressed Temperatures
Authors: Yong R. , Taylor L. O. , Warkentin B. P. 
Published: August 2006

AbstractSwelling pressures of oriented samples of sodium montmorillonite at 10−4 and 10−2 M NaCl in the pore-water were measured at controlled temperatures ranging from 1°C to 23°C. The specially designed apparatus allowed swelling against a movable piston connected to a mercury manometer through which the ambient pressure was applied.A decrease in swelling pressure with decrease in temperature is predicted theoretically from the Gouy-Chapman theory, taking the variation of temperature and dielectric constant into account. At a salt concentration of 10−4 M NaCl, the measured swelling pressure at 120 Å average interparticle distance decreased from 48 cm of mercury at 23°C to 35 cm at 1°C, while the corresponding calculated pressure decrease was from 48 to 40 cm. While the measured pressures fell below calculated values at higher distances, the influence of temperature remained consistent.At 10−2 M NaCl, a decrease in measured swelling pressure with decreasing temperature also occurred, but the measured swelling pressures were much higher than those predicted theoretically. Corrections were calculated, based upon the salt concentrations required by the theory to give the experimentally measured swelling pressures at room temperature. These were substituted into the approximate Langmuir solution of the combined Poisson-Boltzmann equation to describe the swelling pressure at 10−2 M NaCl. With these corrections, the calculated swelling pressure at 120 Å average interparticle distance decreased from 30 cm at 23°C to 26 cm at 1°C while the measured pressure decreased from 30 to 23 cm. This agreement between the corrected, calculated pressure and measured pressure held from 100 to 250 Å interparticle spacing.
Studies in Fractionated Montmorillonite Suspensions
Authors: Mungan Necmettin , Jessen Frank W. 
Published: August 2006

AbstractFour natural bentonites, from Texas, Wyoming, Mexico, and Puerto Rico, have been fractionated by use of a super-centrifuge. The fractions have been investigated for base exchange capacity, apparent density, X-ray diffraction character and gel strengths of their suspensions.Based on (001) spacings from X-ray diffraction and cation composition from ammonium acetate base exchange data, it was found that upon fractionation, clays of heterogeneous cation composition divide into two groups. Fractions larger than 0.150 micron contain the divalent cations Ca2+-Mg2+, while the finer fractions contain the monovalent cation Na+. Based on indirect evidence provided by X-ray diffraction, particle size fractionation, and gel strength, and correlation of the data with the literature, it is concluded that Na+clays exist as unit layers in suspensions while Ca2+-Mg2+particles are aggregates of a few layers.Base exchange capacity and density were found to be independent of particle size.A new structure is postulated and proposed for aqueous montmorillonite gels. This structure, descriptively called “hinge,” comprises clay particles oriented randomly to form a network in which each particle is hinged to other particles through sharing of bound particle-water.
Cation Exchange in Kaolinite-Iron Oxide Systems
Authors: Thomas Grant W. , Swoboda Allen R. 
Published: August 2006

AbstbactKaolinite, to which iron oxides had been added by heating with FeCl3 solution, was studied with regard to its cation exchange capacity. It was observed that net cations held (cations less anions) varied directly with pH. Cations and anions are removed in equivalent amounts when the clays are washed with water. Removal of exchangeable cations proceeds as the last anions are removed. As a consequence, the negative sites may become saturated with non-exchangeable hydroxy-aluminum ions. To obtain the true CEC of a kaolinite-iron oxide system, it is necessary to estimate the amount of nonexchangeable hydroxy-aluminum by conductometric titration.
The Bentonites of Cabo de Gata (Southeast Spain) and of Guelaya Volcanic Province (North Morocco)
Authors: Vivaldi J. L. Martin 
Published: August 2006

AbstractVolcanic activity was important in Spain during the second half of the Cenozoic Era. It was closely related to the late kinematic and subsequent periods of the Alpidic orogenic cycle. Manifestations of the volcanic activity are seen in several parts of the Iberian Peninsula, but the main ones were confined to a few rather individualized zones. Cabo de Gata, Cartagena, and Mazarrón show a strong similarity, as does the Guelaya volcanic province, Morocco. The rocks (rhyolites, dacites and andesites) are clearly calcalkaline and, in many places, strong contamination processes have been demonstrated. The eruptions were, at least in part, fissural and fill important fractures, mainly northeast-southwest. They occurred just after the more important folding in the Betic-Riffien orogen. In these regions bentonite has formed by alteration of volcanic material.The most important deposits are in Sierra of Nijar and Gata (Almería, Spain) and in the Monte Tidinit (Morocco). The Cabo de Gata bentonites are composed mainly of calcic and calcosodic montmorillonites. Palygorskite has been found in some places.The bentonite of the Monte Tidinit is mainly calcium montmorillonite but some samples contain cristobalite. In Monte Maazza there is also a sedimentary deposit, consisting of a complex mixture of endellite, halloysite, gibbsite, montmorillonite and alunite—probably of hydrothermal origin. Halloysito is the main component: it is accompanied by gibbsite in the bottom layers and by montmorillonite and alunite in the top ones.The ground clay, after processing by cation exchange or acid activation, is used for several industrial products, such as soaps and detergents, cosmetics and pharmacy; but the main use is for drilling muds, foundry molds, and clarification of mineral and vegetable oils.All the bentonites are amenable to acid activation but the natural mixture of halloysite and montmorillonite from Monte Maazza gave the best results in tests on lubricating oils at a laboratory scale.Research still in progress on the rheology of suspensions of the Almeréa bentonite contaminated with electrolytes gave interesting results using several thinner and filter oss control agents.
Kinetics and Mechanisms of Dehydration and Recrystallization of Serpentine—I
Authors: Brindley G. W. , Hayami Ryozo 
Published: August 2006

AbstractDehydration and recrystallization reactions of fine and coarse powders and also of massive samples of serpentine under isothermal heating conditions in air are followed by thermobalance measurements and by X-ray diffraction intensities. The rate of recrystallization to forsterite is shown to have an inverse relationship to the rate of dehydration. This result is interpreted in terms of the damage inflicted on the crystal structure of serpentine by the dehydration reaction; the more slowly this reaction occurs, the more readily is forsterite formed as a result of the topotactic relationship between forsterite and serpentine. The surface layers of particles and massive samples of serpentine which dehydrate readily appear to be highly disordered and consequently recrystallize to forsterite very slowly. The corresponding phenomena exhibited by kaolinite are discussed and compared with those by serpentine.
High-Temperature D.T.A. and X-Ray Diffraction Studies of Reactions
Authors: Wahl F. M. , Grim R. E. 
Published: August 2006

AbstractSeveral reactions which take place in clay minerals at elevated temperatures were investigated by D.T.A. and continuous high-temperature X-ray diffraction. The combination of these techniques was used to examine the energy changes and phase transformations that occur in kaolinite, halloysite, illite, and montmorillonite at temperatures up to 1450°C.Diffraction data obtained from these minerals as they were heated are used to interpret the nature of the structural transitions, and new phase developments in two-layer type clay minerals are compared with similar developments in three-layer type clays.Continuous diffraction is used to detect changes that take place in the firing history of a clay in which small amounts of chemical impurities or other mineralizing substances are present or have been added. Several chemical impurities were added to each of the clays to determine their ability to either enhance or retard structural transition and new mineral development upon firing. The effects which these additives have on predicted structural changes are illustrated and are interpreted in lieu of chemical and structural requirements.
Halloysitic Underclay and Amorphous Inorganic Matter in Hawaii
Authors: Patterson Sam H. 
Published: August 2006

AbstractPlastic clay deposits underlie peat beds in several swamps on the island of Kauai, Hawaii. These underclays are appreciably different in mineralogical and chemical composition from the associated well-drained weathered rocks (saprolite). The underclay is much higher in silica and lower in iron oxide than the saprolite. The underclay is composed chiefly of halloysite minerals, with minor amounts of gibbsite, anatase, quartz, goethite, and illite. The saprolite is predominately gibbsite, goethite, and hematite, with minor amounts of titaniferous magnetite, anatase, and halloysite minerals. Apparently both the clay and saprolite have formed by weathering from the same type of parent rock and have undergone similar geologic histories; therefore, differences in drainage and the presence or absence of an overlying peat layer appear to be the principal genetic variables.The underclay and saprolite are believed to contain amorphous gels and allophane because X-ray intensities for many samples are low, and estimated amounts of identifiable minerals are not adequate to account for the whole samples. Attempts to isolate the amorphous materials in samples from Kauai have not been successful, but both an alumina-silica gel and allophane were found in saprolite at one locality on Maui, Hawaii. These materials were collected from the face of a freshly bull-dozed roadcut at a depth of 2 to 6 ft. They occur as veins and as fillings and coatings on vesicles, vugs, and cracks in a dark-brown saprolite closely associated with hard basalt. The allophane is white, and most of it is covered by a clear or light-colored gel. Some of the gel occurs in clear irregular masses ranging in size from microscopic specks to about one-fourth inch in diameter and is similar to a mass of frog eggs or thick gelatin. Some occurs as light-grayish brown, paper-thin laminae that extend along cracks for several inches.Both the allophane and dried gel are similar in composition, containing approximately 50 per cent alumina and 22 to 26 per cent silica. The close association and similar composition indicate that allophane forms from the alumina-silica gel. Gibbsite and halloysite minerals occur in a manner very similar to that of the allophane and gel, suggesting that these amorphous materials are intermediate phases in the formation of gibbsite and halloysite. This is supported by the small amount of gibbsite present in the dried gel.
Petrogenesis of Bentonites
Authors: Slaughter M. 
Published: August 2006

AbstractThe formation of typical bentonites occurs in two stages. The first stage comprises the development, transportation, and deposition of the volcanic ash, which determines the geometry and structure of the bentonite rock and influences the alteration of the ash during the second stage. The second stage encompasses the alteration of volcanic glass to montmorillonite and other minerals.The distribution of ash particles in the bentonite beds of Wyoming is satisfactorily explained by a theoretical model based on equations similar to heat flow equations. An extended model, assuming a disk-shaped volcanic cloud containing ash particles, also accounts for the geometrical shapes and geographic variations of the textural parameters of the bentonite beds.The alteration of Wyoming bentonite ashes to montmorillonite occurred undoubtedly at low temperatures in an aqueous environment. Petrologic evidence indicates that all of the Wyoming ashes and many ashes deposited elsewhere contained sufficient magnesium to form montmorillonite with no addition necessary from without. Also evidence indicates variations of pH of perhaps 5 to 8 made little difference in the alteration products of the ashes.Laboratory evidence of the processes and products of alteration of ashes to bentonite accord with field observation. With simplifying assumptions, the formation of montmorillonite from volcanic glass may be elucidated from the viewpoint of the stability of montmorillonite with respect to other similar minerals. The results of theoretical calculations of the mineral stabilities will be presented. Three energy parameters will be considered: the Coulomb energy, Van der Waals’ repulsion, and the London energy Thermal motion of the atoms will be taken into account.
Spatial Relations Between Air Bubbles and Flocculated Kaolinite and Dickite
Authors: Okuda Susumu , Williamson William O. 
Published: August 2006

AbstractThe optical microscope revealed that when air-saturated dilute aqueous suspensions of coarse kaolinite and dickite crystals were evacuated, negatively charged bubbles formed on and between the particles, which showed characteristic spatial relations to the bubbles and to each other.Crystals leached with HCl developed edge-to-face flocculation over a wide acid pH range and presented their edges to the bubbles, indicating positive edge-charges. The addition of Na-montmorillonite reduced the number of particles adhering to the bubbles and impeded the edge-to-face flocculation.In slightly acid suspensions, the particles became adlineated to form chains linking bubbles together or dependent from them.At pH <3 or >7 the bubbles retained relatively few particles probably because the negative charge density on bubbles decreased at pH <3, while the crystals lost their positive edge charges at pH>7. At pH>7 crystals were often retained by their basal surfaces.Crystals saturated with Ca2+ or Pb2+ showed face-to-face flocculation and tended to present their basal surfaces to the bubbles. The relatively large amounts of Ca- and particularly of Pb-clay secured by the bubbles may be associated with the lessened wettability caused by these cations.The mantles of adherent particles affected the stability of the bubbles, both by preventing the coalescence of neighbors, and by lengthening the diffusion paths for dissolved air passing from smaller to larger bubbles.
Thermodynamics of the Various High-Temperature Reactions of Kaolinite
Authors: Soliman M. R. 
Published: August 2006

AbstractIn spite of the fact that the kaolinite-mullite reaction series had been the subject of extensive investigations since the work of Le Chatelier in 1887, nevertheless many-problems are still remaining. One of the major problems is the interpretation of the first exothermic peak at 980°C.Based on sufficiently accurate thermodynamic data of kaolinite and its high temperature products, equations were derived, expressing the changes of free energy with temperature for all various possible reactions of kaolinite between 298°K and 2300°K.The most favourable reaction at 980°C, (1253°K), is that which yields mullite and ß quartz.The exothermic peak at 980°C is neither due to crystallization of γAl2O3 and SiO2 nor to mullite, γAl2O3 and SiO2 but most probably due to crystallization of mullite and silica. The values of ΔG1250°K are: -40,919, -88,991 and -105,022 cal/mol respectively.
Inorganic pH Dependent Cation Exchange Charge of Soils
Authors: Volk V. V. , Jackson M. L. 
Published: August 2006

AbstractSodium hydroxide titration curves were determined on H resin treated montmorillonite, untreated acid and neutral soils of different origins and on the same soils with an H resin treatment. The acid montmorillonite titration curve reveals four buffer ranges corresponding to hydronium ions (range I), monomelic trivalent aluminum ions Range II), and two pH dependent charge ranges. Untreated acid soils contained pH dependent buffer zones governed jointly by the organic fraction, the soil pH, the presence of monomeric trivalent aluminum, and the exchange blocking mechanisms of other cations. Following an H resin treatment, soils containing less than 2 per cent of organic matter exhibited a clearly defined third buffer range (Range III) from pH 5.5 to 7.6. The inflection points are masked in the pH dependent buffer range in soils containing more than 2 per cent organic matter. The presence of added aluminum increased the pH dependent charge in an acidified montmorillonite while added ferric iron slightly decreased it. The natural acid weathering processes in soils result in some blocking of pH dependent charge as in Dodge soil of Wisconsin (KCl pH 4.5). When greater acidity develops, a large pH dependent charge results, as in Coolville soil in Ohio (KCl pH 4.0), and the lime requirement of the soil thus increases greatly.