bluuebunny/crossref_metadata_2025_split huggingface dataset:
Freeze-Dried and Thawed Clays
Authors: Lincoln James , Tettenhorst Rodney 
Published: August 2006

AbstractHeating montmorillonites to their dehydroxylation temperatures destroyed their ability to form an aerogel. The breakdown of the aerogel structure coincided with the loss of hydroxyl water from the montmorillonite. Apparently, this loss of water was accompanied by a loss of the layer charge. Particle size and aerogel-forming ability appear to be inversely related properties for at least some montmorillonites. The kaolinite investigated did not form an aerogel in any size fraction. The formation of montmorillonite aerogels from various concentrations of clay was investigated. The texture and physical appearance of these aerogels was examined and presented herein.Thawed clay suspensions exhibited a variety of behaviors. The Volclay bentonite, which apparently formed a true sol was unaffected by freezing. In all other clays at least some of the fine clay particles agglomerated on freezing and large clumps were observed dropping out of the melting ice. After stirring the thawed suspensions less clay was dispersed than in the unfrozen suspension counterparts. Addition of a dispersing agent to these suspensions caused more clay to remain dispersed following freezing-thawing-stirring.
Low Temperature Hydrothermal Synthesis from Dolomite or Calcite, Quartz and Kaolinite
Authors: Bayliss P. , Levinson A. A. 
Published: August 2006

AbstractDolomite or calcite, quartz and kaolinite in various proportions were reacted at 250–300°C temperatures and pressures up to 90 bars in a hydrous environment. Reactions which approached completion produced talc, calcite, montmorillonite, anorthite (both metastable hexagonal and stable triclinic polymorphs) and the rare Ca-zeolite, garronite. These reactions are applicable to diagenesis, low-grade metamorphism and hydrothermal alteration.
Flint Clay by Hydrothermal Alteration of Sedimentary Rock in Mexico
Authors: Hanson Robert F. , Keller W. D. 
Published: August 2006

AbstractThis paper documents the first report of flint clay in Mexico, located at Estola, Guerrero, 199 km south of Mexico City, on Mexico Highway 95. It is the first report (known to the writers) of flint clay formed by hydrothermal alteration. It describes the in-situ alteration of a calcareous, silty shale to flint clay (well-ordered kaolinite).The changes during alteration are mineralogical, chemical, and structural. Calcite, comprising about one-third of the shale, quartz and probably some feldspar comprising a scant third, and a mixture of greenish-yellow (limonitic) clay minerals are dissolved or altered ultimately to white kaolinite (monomineralic). Calcium carbonate, free and combined silica, and iron compounds are dissolved, while simultaneously the alumina is relatively enriched. The fissility, inequigraularity, and cementitous fabric of shale are changed to the massively homogeneous, finegrained, interlocking fabric that is typical of flint clay.The sequence of changes, which overlap, are; (1) dissolution of carbonate minerals, (2) mobility of iron, replacement of quartz and feldspar by kaolinite; and (3) intensive “digestion” of rock substance to homogeneous, essentially monomineralic, kaolinite flint clay. Alunite, and secondary vein-calcite or gypsum may accompany the flint clay.This occurrence lends support to the concent that flint clay is formed from presumably only sedimentary parent rock.
Sequential Active Alteration of Rhyolitic Volcanic Rock to Endellite and a Precursor Phase of it at a Spring in Michoacan, Mexico
Authors: Keller W. D. , Hanson Robert F. , Huang W. H. , Cervantes A. 
Published: August 2006

AbstractSequential alteration of volcanic rock of rhyolitic composition to a precursor of endellite, and thence to tubular endellite, may be observed at a hot spring about 27 km north of Ciudad Hidalgo, Michoacan, Mexico. Ojo Caliente de Laguna Larga (or Verde) yields H2S-SO2-containing water, temperature about 45°C pH 3·5–3·7, from multiple orifices in vesicular and slabby rock with which the water reacts.First-stage alteration of the rock consisted of permeation and dissolution, accompanied by deposition of clay substance in vesicle walls. The clay substance, although “amorphous” to X-rays, yields a weak DTA of endellite, and kaolinite. It is interpreted as a precursor of endellite. Further reaction included continued filling of vesicles and spreading argillation which coalesced between vesicles and other rock pores. Ultimately, the rock was completely “digested” to well-defined endellites.Strong desilication and depotassication of the rock is indicated by the dissolved substances in the spring water: Si 59·1 (equivalent to 127 SiO2) ug/ml: Al, 1·63; Fe, 0·65: Mg, 0·21: Ca, 178: Na, 0·73: K, 13·7. Despite high K+, predominantly high H+ and Al3+ induce formation of endellite. The clay-water system accords well with stability diagrams.Allophane-endellite in Indiana and endellite at Stanford, Kentucky, are formed from cold, strongly acid, meteoric-water solutions high in Si and Al relative to kaolinite dissolved in water. Factors of genesis common to both hot- and cold-water endellite are cited, suggesting that they are premissively critical, but not necessarily restrictive, to the origin of endellite.
Mixed-Layer Kaolinite—Montmorillonite from the Yucatan Peninsula, Mexico
Authors: Schultz L. G. , Shepard A. O. , Blackmon P. D. , Starkey H. C. 
Published: August 2006

AbstractClay beds 1–2 m thick and interbedded with marine limestones probably of early Eocene age are composed of nearly pure mixed-layer kaolinite-montmorillonite. Particle size studies, electron micrographs, X-ray diffraction studies, chemical analyses, cation exchange experiments, DTA, and TGA indicate that clays from three different localities contain roughly equal proportions of randomly interlayered kaolinite and montmorillonite layers. The montmorillonite structural formulas average K0·2Na0·2Ca0·2Mg0·2(Al2·5Fe1·03+Mg0·5)(Al0·75Si7.25)O20+(OH)4−, with a deficiency of structural (OH) in either the montmorillonite or kaolinite layers. Nonexchangeable K+ indicates that a few layers are mica-like. Crystals are mostly round plates 1/10 to 1/20 μ across. The feature most diagnostic of the mixed-layer character is an X-ray reflection near 8 Å after heating at 300°C. The clays are inferred to have developed by weathering of volcanic ash and subsequent erosion and deposition in protected nearshore basins.
Relation of Potassium Exchange and Fixation to Degree of Weathering and Organic Matter Content in Micaceous Clays of Podzol Soils
Authors: Ross G. J. 
Published: August 2006

AbstractThe rates of K exchange of untreated and peroxide-treated micaceous clays from five Podzol soils of increasing degrees of weathering were determined using sodium tetraphenyl boron. In addition, the amounts of K fixed against NH4 were measured. The Ae horizon clays of these soils contained mainly interstratified mica-vermiculite-montmorillonite whereas the C horizon clays contained mica of a more discrete nature.As was expected, there was an inverse relationship between rates of K exchange and degrees of weathering of the Ae horizon clays. However, in the samples from each of these soils except in those of the most weathered one, the K exchange rate of the interstratified mica from the Ae horizon was higher than that of the less weathered, more discrete mica from the corresponding C horizon. The abundance of hydrated edges and layers exposing K exchange sites in the Ae horizon micas probably contributed to their higher rates of K exchange. Amounts of K fixed in the Ae horizon clays were not related to degrees of weathering.Removal of organic matter from the Ae horizon clays by peroxide considerably increased both the rates of K exchanged and the amounts of K fixed. These increases were attributed to the elimination of a blocking effect of adsorbed organic matter on K exchange and fixation.
Cation Migration Into Empty Octahedral Sites and Surface Properties of Clays
Authors: Calvet R. , Prost R. 
Published: August 2006

AbstractThe migration of small cations into the empty octahedral sites of dioctahedral clays allows one to study the local effects in the trioctahedral structure and the consequences of the exchange capacity decrease on the solvation properties. The results concern essentially the montmorillonite saturated by lithium. Computations based on a point charge model shows the necessity for the OH groups to undergo a reorientation when the lithium ions are within the octahedral sites. This change of orientation was studied by i.r. spectroscopy which permits one to estimate the amounts of lithium present in the structure. By analogy with i.r. results obtained for the Li, Mg, Ca and K montmorillonites, one can say that the non-exchangeable lithium which is not within the octahedral sites must be in the bottom of the hexagonal cavities. Moreover, it is shown that the solvation properties of the clay depend on the number of exchangeable cations and on the nature of the solvent. The clay does not swell with water when the amount of exchangeable cation is lower than 50 per cent of the exchange capacity. This limit is 30 per cent with glycerol, and 20 per cent with ethylene glycol.
Antigorite—Its Occurrence As a Clay Mineral
Authors: Brindley G. W. , Santos Persio de Souza 
Published: August 2006

AbstractA white clay from the Jatoba talc mine, Castro, Paraná, Brazil, is shown by chemical analysis, X-ray and electron diffraction, and by thermal analysis to be essentially pure antigorite in the strict sense of the term. Single crystal electron diffraction patterns give various values for the long a parameter, with 43·5 Å perhaps the most commonly occurring, b = 9·25 Å, d(001) = 7·25 Å. X-ray powder diffraction gives d(001) = 7·26 Å and b = 9·23 A. Electron micrographs show irregular platy and lath-like crystals of about 0·5–2 μ size with large development of (001) planes and with b in the direction of elongation. Other crystals are observed with very unusual forms, some having holes through them. They show mainly 0kl diffraction patterns and lie with the basal (001) planes normal to the stage of the instrument. The chemical analysis agrees closely with the ideal serpentine composition and the differential thermal analysis curve is consistent with antigorite.
The Effect of Exchangeable Cations on the Sorption of Chlorophyllin By Montmorillonite
Authors: Kaufherr N. , Yariv S. , Heller L. 
Published: August 2006

AbstractThe sorption of commercial K-Cu chlorophyllin by a sample of montmorillonite saturated with different exchange ions was studied. The organic anions are sorbed on external surfaces while K displaces most of the exchangeable cations. The samples sorb the constituents of chlorophyllin selectively and in different amounts, depending on the exchangeable cations of the clay. These also affect the amount of material peptized and the relative orientation and aggregation of the particles.
Surface Chemistry of Thermally Decomposed Organo-Montmorillonite Complexes
Authors: Slabaugh W. H. 
Published: August 2006

AbstractThe hydrophilic-hydrophobic properties of four thermally decomposed organoclays, the octadecylammonium-, the dimethylaryloctadecylammonium-, and the dimethyldioctadecylammonium-bentonites and the dimethyldioctadecylammonium-hectorite, were examined through adsorption isotherms with nitrogen, water vapor, and hexane. Along with DTA and TGA results, these clay complexes appear to undergo transitions from low to higher degrees of hydrophilicity as more and more of the hydrocarbon chains are dehydrogenated at successive temperatures up to 400°C.
Diagenetic Development of Kaolinite
Authors: Curtis C. D. , Spears D. A. 
Published: August 2006

AbstractExperimental solubility data for gibbsite and kaolinite are reviewed and applied to the problem of gibbsite stability within the natural environment. It is concluded that free alumina compounds formed (only) in lateritic soils will tend to silicify spontaneously in all sedimentary environments. This metasomatic reaction should be accompanied by massive volume expansion: unusual textures are to be anticipated.Petrographic and field descriptions of a number of ancient kaolinitic sediments (some with, some without free alumina) are reviewed. It is concluded that silicification of hydrated aluminum oxides was an important mechanism of kaolinite formation in ancient sediments and that free alumina compounds persist only as a result of the unusual volume expansion associated with kaolinite formation.
Cristobalite Authigenic Origin in Relation to Montmorillonite and Quartz Origin in Bentonites
Authors: Henderson J. H. , Jackson M. L. , Syers J. K. , Clayton R. N. , Rex R. W. 
Published: August 2006

AbstractThree kinds of opal-cristobalite, differentiated by the sharpness of the 4·1 Å XRD peak, were isolated from the Helms (Texas) bentonite by selective chemical dissolution followed by specific gravity separation. The δ18O value (oxygen isotope abundance) for these cristobalite isolates ranged from approximately 26–30‰ (parts per thousand), increasing with increased breadth of the 4·1 Å XRD peak. Opal-cristobalite isolated from the Monterey diatomite had a δ18O value of 34‰. These δ18O values are in the range for Cretaceous cherts (approximately 32‰) and are unlike the values of 9–11‰ obtained for low-cristobalite (XRD peaks at 4·05, 3·13, 2·4, and 2·49) formed hydrothermally or isolated from the vesicles of obsidian. The morphology pseudomorphic after diatoms, observed with the scanning electron microscope, was more apparent in the opal-cristobalite from the Monterey diatomite of Miocene age (approximately 10 million yr old) than in the spongy textured opal-cristobalite from the Helms bentonite, reflecting the 40 million yr available for crystallization since Upper Eocene.The oxygen isotope abundance of Helms montmorillonite (δ18O = 26‰) indicates that it was formed in sea water while the δ18O values of the associated opal-cristobalite indicate that this SiO2 polymorph probably formed at approximately 25°C in meteoric water. Although both cristobalite and mont-montmorillonite in the bentonite were authigenic, the crystallization of the SiO2 phase apparently required a considerably longer period and occurred mainly after tectonic uplift.In contrast to the results for cristobalite, quartz from the Helms and Upton (Wyoming) bentonites had δ18O values of 15 and 21‰ respectively. Such intermediate values, similar to those of aerosolic dusts of the Northern Hemisphere, loess, and many fluvial sediments and shales of the North Central United States (U.S.A.), preclude either a completely authigenic or a completely igneous origin for the quartz. These values probably result from a mixing of quartz from high and low temperature sources, detritally added to the ash or bentonite bed.
Microstructure and Pore Structure of Impact-Compacted Clays
Authors: Diamond Sidney 
Published: August 2006

AbstractThe microstructures of impact-compacted kaolinite and illite clays, after drying, were investigated by pore size-distribution measurements, X-ray orientation determinations, and scanning electron microscopy. Clays compacted on the dry side of the optimum moisture content exhibited a domain structure with adjacent domains largely separated by micrometer-size interdomain voids; clays compacted at or above the optimum moisture content showed a more nearly massive structure, large interdomain voids being absent. Parallel orientation was observed within domains, but neighboring domains were generally tilted with respect to each other. In kaolinite compacted on the wet side of optimum, regions of local parallel orientation could be identified at high magnification as domain units. A significant volume of 200 Å–800 Å dia. pores in this clay was identified with spaces observed between the kaolinite plates within domains, for samples compacted both on the wet and dry sides of optimum. The subdomain structure was tentatively classified as “intergrown” in character. (001)/(020), (002)/(020), (001)/(060), and (002)/(060) orientation indices were calculated for the compacted kaolinite and compared with analogous measurements for fully-random and fully-oriented specimens of the same clay. The results indicated only a small degree of preferential orientation normal to the axis of compaction, with little difference between samples compacted either wet or dry of optimum. These results were consistent with scanning electron microscope interpretations, which suggested that the domains did not appear to orient themselves significantly under the influence of the compaction employed.
Swelling Characteristics of Compacted, Expansive Soils
Authors: Nayak N. V. , Christensen R. W. 
Published: August 2006

AbstractThe limitations of existing methods for the prediction of swelling behavior of compacted soils are examined. Both the purely theoretical approach and the purely empirical approach are found to be inadequate. The present study is based on a semi-empirical approach in which a model of swelling behavior is developed leading to equations relating swelling potential or swelling pressure of a compacted soil to its plasticity index, clay content and initial molding water content. The model is based on the concepts of the diffuse double layer, modified by introducing empirical constants to account for elastic swelling effects and other limitations involved in the direct application of double layer theory to real soils. The empirical constants are evaluated from the results of experimental investigations carried out on a large number of soil samples representing a wide variation of clay content as well as consistency limits.It is shown that the predicted values of the swelling potential and swelling pressure based on the proposed model agree closely with the experimental results of this study and those reported in the literature. Furthermore, the equations developed in this study are of a more general nature and appear to be applicable to a larger range of soil types than those previously published.
Adsorption Studies on Kaolinites — II Adsorption of Amines
Authors: Conley Robert F. , Lloyd Mary K. 
Published: August 2006

AbstractAn investigation of the reaction between amines and hydrogen kaolinites having a broad range of crystallinites and particle sizes has been made. Aqueous and non-aqueous adsorption isotherms, conductivity titrations, rheological measurements and sediment volume studies give strong evidence that edge sites are dominantly involved in the reaction and basal surfaces remain essentially unaltered. The acid-base reaction produces a localized adduct rather than an ionized, protonated amine. The amine-hydrate adduct adsorbs with greatly modified geometry.
Three Techniques for Fabric Viewing as Applied to Shear Distortion of a Clay
Authors: McKyes Edward , Yong Raymond N. 
Published: August 2006

AbstractA knowledge of the microscopic physical behavior of soils is important and necessary for the correct interpretation of observed macroscopic deformations in soil bodies. This study was designed to determine the particular pattern and distribution of extensive fabric alteration accompanying shear strains in a clay specimen subjected to triaxial stress combinations. The techniques used for observing these microscopic features were polarized light microscopy of thin sections from Carbowax-fixed clay samples, scanning electron microscopy of thinly coated cleavage surfaces in vacuum desiccated specimens, and transmission electron microscopy of metal-shadowed carbon replicas made of similar cleavage surfaces. All three methods showed that the zone of extensive fabric alteration in the triaxially sheared bodies was planar and had an average thickness of about 30 μ.Most clay particles in the zone were aligned parallel to the zone direction. The results of the study also demonstrated the particular merits of each of the three techniques for fabric viewing.
Effects of Amorphous Constituents on Some Mineralogical and Chemical Properties of a Panamanian Latosol
Authors: Townsend F. C. , Reed L. W. 
Published: August 2006

AbstractThis study was an investigation of the effects of sesquioxide constituents on some mineralogical and physiochemical properties of a Panamanian latosol.Latosols are soils characterized by high concentrations of iron and aluminum oxides and a general absence of free silica and alkaline earths.X-ray diffraction studies revealed sesquioxide coatings existed on the surfaces of the clay minerals. Mineralogically, the soil was composed of kaolin, amorphous minerals, hydrated iron and aluminum oxides, free silica, quartz grains, and magnetite. The results of DTA data suggested the presence of amorphous colloids in the soil. This suggestion was subsequently confirmed by selective dissolution analysis which revealed the unexpected presence of 17% amorphous silica in the coarse clay size fraction. Grain size analysis and scanning electron microscopy studies showed that the clay minerals are probably agglomerated by the sesquioxides into silt size clusters. CEC values obtained were primarily attributed to the amorphous colloids rather than the crystalline clay minerals because the sesquioxides probably partially blocked the exchange sites of the clays.Removal of the iron and aluminum oxides by sodium dithionite citrate-bicarbonate procedures (Mehra and Jackson, 1960), (a) sharpened and exposed previously “masked” X-ray diffraction peaks, (b) disaggregated the clay clusters producing greater amounts of clay size particles, and (c) altered the Cation Exchange Capacity (CEC) and water retention characteristics of the soil constituents.This investigation demonstrated that amorphous silica and iron and aluminum oxides greatly influence the properties of this latosol by coating and aggregating the clay minerals. These sesquioxide coatings suppress the ordinary behavioral characteristics of the indigenous clay minerals and consequently the observed behavior of the soil is dominated by the amorphous constituents.
Trace Element Concentration in Amorphous Clays of Volcanic Ash Soils in Oregon
Authors: Borchardt G. A. , Harward M. E. , Knox E. G. 
Published: August 2006

AbstractClay fractions in soils from a transect of the Mazama ash deposit (6600-yr-old) contained more than 80% amorphous material. Instrumental neutron activation analysis was used to compare the trace element composition of the soil clay with the unweathered volcanic glass. The clay fractions had only 10% as much Na as the volcanic glass. Conversely, the rare earth element concentrations were about three times greater and the transition metal concentrations were up to nine times greater in the clay than in the glass. The < 2μ size fraction therefore contained mostly weathering products rather than fine glass.The abundances of Cr, Co, Sc, and Fe in the clay fraction decreased with depth. The Sc/Fe ratio was approximately 4 × 10−4 for both clay and the unweathered glass. The relationship between elemental concentration in clay and fine sand size separates from the same soil horizons indicated that the clay exists in association with the larger size particles, probably as coatings.Dilute nitric acid removed about 80% of the rare earth elements La, Nd, Sm, Eu, Tb, Yb, and Lu from the clay. Deferration was necessary to remove Ce, a rare earth element that forms insoluble oxides upon oxidation to the Ce4+ state. The residue of the KOH dissolution treatment contained 2:1 layer silicates that may be derived from primary biotite.