Showing papers in "Clays and Clay Minerals in 1968"

Hydroxy Interlayers in Expansible Layer Silicates

Abstract: Vermiculites and smectites in soils and sediments are frequently partially interlayered or “chloritized”. Dioctahedral expansible layer silicates are those most frequently interlayered, and hydroxy-Al appears to be the principal component of the non-exchangeable interlayer material. The most favorable soil conditions for interlayer formation appear to be: moderate pH (4·6–5·8), frequent wetting and drying cycles, and low organic matter content. In marine sediments, hydroxy-Mg interlayering may be significant. Soil-derived clays containing partially filled hydroxy-Al “brucite” sheets may be filled out with hydroxy-Mg. Under reducing conditions, hydroxy-Fe interlayers may be important. Depending on the OH/Al ratio and Al content of hydroxy-Al interlayers, expansible layer silicate may either promote or retard the formation of gibbsite. Interlayered expansible layer silicates also may be precursors to kaolinite.

Surface Acidity of Smectites in Relation to Hydration, Exchangeable Cation, and Structure*

Abstract: Equilibrium studies on clay films exposed to N H3 and H20 vapors demonstrate the effect of exchangeable cations on surface acidity and its relationship to hydration. At a relative humidity of 98 per cent the order of acidity on the clay surface as indicated by protonation of N H3 was AI > Mg > Ca = Li > Na = K for Wyoming bentonite and AI > Mg > Li > Ca = Na = K for nontronite. At a relative humidity of 20 per cent, however, the order was AI= Mg > Ca > Li > Na > K for the bentonite and AI = Mg > Li > Ca > Na > K for nontronite. The largest change in proton donation properties due to hydration effects was in the calcium clays. For Ca-bentonite the NH4 + formation was 16 me/100 g at 98 per cent and 80 me/100 g at 20 per cent relative humidity. In Ca-nontronite, the NH4 § formation was 14 and 64 me/100 g for the wet and dry systems respectively. The differences in proton donation between the bentonite and nontronite clays are believed to be due to charge site location and its effects on ion hydration. The NH4 + formed by the protonation process seemed to exist in different environments in the bentonite and nontronite as indicated in the i.r. absorption spectra.

Clay minerals in hydrothermally altered rocks at wairakei, new zealand*

Abstract: Geothermal fluid discharged by steam wells, which have been core drilled to depths as much as 4500 ft at Wairakei, New Zealand, has altered Pliocene to Pleistocene, silicic, mainly glassy volcanics and related aqueous tuffs and breccias. Measured temperatures (max. 265°C) indicate epithermal to mesothermal conditions in buried fault fissures, the locus of both the hydrothermal fluid and most intense alteration. A supergene kaolinite alteration zone is distinguished from hypogene Ca-montmorillonite and combined micaceous and chloritic zones. The hypogene zones are usually wide and are temperature dependent and localized along fault fissures. Other common hypogene minerals are alkali feldspars, wairakite, epidote, quartz, calcite, laumontite, ptilolite, pyrite and pyrrhotite. Prehnite is rare. The micaceous clay minerals include illite (about 10 A) and a series of random mixed-layer illite-montmorillonites with d(001) values ranging from 10·28 to 12·45 A. The amount of interstratified montmorillonite is related to temperature and fault fissures. Apart from rare mixed-layer swelling chlorite, the Fe-rich chloritic clay shows little or no variation in its composition. Both the micaceous clays and the chloritic clay result from alteration of earlier formed Ca-montmorillonite. The stability of hydrothermal minerals is controlled by the temperature and chemical composition of the geothermal fluid ascending along the fault fissures. K-feldspar but not albite is deposited on fissure walls, but both alkali feldspars replace primary soda-lime plagioclase in the wall rock. The absence of albite on fissure walls is ascribed to low aqueous mNa+/mK+ ratio. Primary quartz is not affected by the altering solution but hydrothermal quartz is deposited on fissure walls and in the wall rock.

Clay Minerals as Electron Acceptors and/or Electron Donors in Organic Reactions

Abstract: Certain clay minerals have the ability to catalyze the polymerization of some unsaturated organic Compounds (styrene, hydroxyethyl methacrylate) and yet to inhibit polymer formation from other closely related monomers (e.g. methyl methacrylate). This apparently contradictory behaviour of the clay minerals can be rationalized in terms of electron accepting and electron donating sites in the silicate layers. The electron acceptor sites are aluminium at crystal edges and transition metals in the higher valency state in the silicate layers; the electron donor sites are transition metals in the lower valency state. The catalyzed polymerizations involve the conversion of the organic molecule to a reactive intermediate; thus where the clay mineral accepts an electron from the vinyl monomer a radicalcation is formed, where the organic compound gains an electron it forms a radicalanion. Examples of these reactions are discussed. The inhibition of polymerization processes involves the conversion of reactive organic intermediates, such as free radicals, which have been formed by heat or radical initiators, to non-reactive entities. For example, loss of an electron from the free radical gives a carbonium ion; in some cases this will not undergo polymerization. An example of this type is the thermal polymerization of methyl methacrylate. The color reactions on clay minerals are useful in predicting the electron accepting or electron donating behaviour of the clay minerals because they proceed by similar mechanisms to the polymerization reactions. For example, the benzidine blue reaction is a one electron transfer from the organic molecule to the electron accepting sites in the mineral (aluminium edges, transition metals in higher valency state). Masking of the crystal edge with a polyphosphate destroys the electron accepting properties of the crystal edge; this technique can be used to control the reactivity of the mineral and to distinguish between the crystal edge and transition metal sites as electron-acceptor sites in the clay minerals.

Boron fixation by illites

Abstract: The mechanism of boron uptake by clays, especially illitic clays, and the factors which control such uptake have long been debated issues. In an attempt to answer some of the questions of the controversy, three illites were treated in solutions containing boron. In the study, boron concen- tration, salinity, temperature, and time were varied independently over rather wide ranges. For the illites studied, irreversible uptake of boron was increased by increasing boron concen- tration, salt concentration, temperature, and time of treatment. The amount of boron which was fixed also varied with the type of illite treated. The amount of fixation was controlled primarily by the specific surface area of the clay and also by the crystallinity, K content, and/or amount of mixed-layer material ("frayed-edge" development?), and apparently was independent of the original boron content of the clay. A two-step mechanism is proposed for boron fixation by illite, consisting of rapid chemical adsorp- tion of the tetrahedral B(OH)+ anion at the "frayed-edge" of the illite flake followed by much slower diffusion of boron into the tetrahedral part of the structure.

Absorption of pyrimidines, purines, and nucleosides by Li-, Na-, Mg-, and Ca-montmorillonite /clay-organic studies XII/.

Abstract: Purines, pyrimidines and nucleosides absorption by Li-, Na-, Mg- and Ca-montmorillonite in aqueous solutions over range pH 2-12 by cation exchange

Analysis of Iron in Layer Silicates by Mossbauer Spectroscopy

Abstract: Analysis of Mossbauer effect in layer silicates provides a spectroscopic method for deter- mining valences and coordination of iron. In this study Mossbauer spectra were obtained for amesite, cronstedtite, nontronite, two glauconites, biotite, lepidomelane, chlorite, minnesotaite, vermiculite, stilpnomelane, and chloritoid. Trivalent iron was detected in tetrahedral coordination. Abundant trivalent iron in octahedral coordination apparently causes quadrupole splitting values of divalent iron in the same mineral to decrease. This phenomenon was noted in cronstedtite and glauconite. In cases where divalent iron predominates in the mineral, the quadrupole splitting is larger. It is generally accepted that ferrous iron is largely in octahedral coordination. This suggests that the octahedral sites may be more distorted when ferric iron is present in the octahedral sheet. In biotite, quadrupole splitting of divalent iron is decreased when trivalent iron is present in tetrahedral sheets. This suggests that there is also more distortion in the octahedral sheet because of iron in tetrahedral positions.

Surface area of montmorillonite from the dynamic sorption of nitrogen and carbon dioxide

Abstract: Surface area determinations were made on a montmorillonite with various cations emplaced on the exchangeable sites, utilizing nitrogen and carbon dioxide as adsorbates at 77°K and 195°K, respectively, in a dynamic system. From the fraction of a Mississippi montmorillonite less than about 1 µ in size, samples were prepared by replacing the original exchangeable cations with Li+, Na+, K+, Rb+, Cs+, Mg++, Ca++, Ba++, and NH/, forming a series of homoionic montmorillonite species. Surface areas from 3-point B.E.T. plots (half-hour adsorption points), with nitrogen as the adsor-bate, ranged from 61 m2/g for Li-montmorillonite to 138 m2/g for Cs-montmorillonite, thus reflecting a certain degree of nitrogen penetration between layers. Complete penetration should theoretically resuit in a surface area of over 300 m2/g for this clay with a nitrogen monolayer between each pair of platelets. The experimental data indicate that the extent of penetration is time-dependent and is also a function of the interlayer forces as governed by the size and charge of the replaceable cation. This finding negates the generally accepted concept that nitrogen at 77°K does not penetrate the layers and provides a measure only of the externa! surface of expandable clay minerais. A further measure of the variation of interlayer forces is provided by the adsorption of carbon dioxide at 195°K. Surface area values ranged from 99 m2/g for Li-montmorillonite to 315 m2/g for Cs-montmorillonite. Although the carbon dioxide molecule is larger than the nitrogen molecule, its greater penetration apparently is a resuit of its being kinetically more energetic (with a larger diffusion coefficient) at its higher adsorption temperature. Similar differences have been found with both adsorbates in the study of microporous substances, such as coal, where activated diffusion is of considerable significance.

Aluminum interlayers in layer silicates; Effect of OH/ Al ratio of Al solution, time of reaction, and type of structure

Abstract: Aluminum intertayers were synthesized under the same experimental conditions in a number of vermiculites and montmorillonites from different sources to determine the effects of the degree of neutralization of AI solutions, the time of reaction, and the' type of structure. Vermiculite fixed AI as well as hydroxy-Al ions in its interlayers, producing a stable 14 ,~ spacing and decreasing its cation exchange capacity considerably. Heating the Al-interlayered vermiculite at 300~ produced an interstratified mixture, indicating that some interlayers collapsed while others did not. The different collapse was attributed to different charge on vermiculite layers. Neither the aging of vermiculite in AI solutions nor their OH/AI ratios changed the stability of the interlayers appreciably. Montmorillonites, on the other hand, did not fix AI ions but fixed appreciable amounts ofhydroxy- AI ions. In addition, the stability of the interlayers in montmorillonite increased on aging in hydroxy- A1 solutions and exceeded the stability of the interlayers produced in vermiculite. To explain the greater stability of montmorillonite interlayers, it was postulated that the more expanded interlayer space in montmorillonite provides a favorable locale for the organization of hydroxy-A1 ions into gibbsite structure while the restricted expansion in vermiculite prevents it.

Formation of Hydroxy-Al and -Fe Interlayers in Montmorillonite and Vermiculite: Influence of Particle Size and Temperature

Abstract: Hydroxy-Al and -Fe interlayers were prepared in "mono-mineralic" fine and coarse clay montmorillonite and coarse clay and silt vermiculite at 3~ and 21~ The formation of hydroxy interlayers was evaluated by X-ray diffraction, cation exchange capacity, and chemical analyses. At comparable particle size and regardless of temperature, the amounts of hydroxy-Al and -Fe interlayers in montmorillonite exceeded by far those formed in vermiculite. Likewise, the aluminum systems exhibited a higher degree of interlayering than iron systems. Within montmorillonite, the amount of hydroxy-A1 and -Fe interlayers increased as the particle size decreased, regardless of temperature. The aluminum interlayered montmorillonite equilibrated at 3~ was characterized by basal spacings of about 17 ,~ after Ca-saturation plus 54 per cent relative humidity. These spacings are larger than those normally observed for smectites. Within vermiculite systems equilibrated at 3~ more hydroxy-AI interlayers were recorded in coarse clay than in silt fraction, whereas at 2 I~ about equal amounts of interlayers were formed. By contrast, hydroxy-Fe interlayer was favored by the silt fraction at both temperature levels. The formation of aluminum interlayers in both minerals increased with increasing temperature. The formation of hydroxy-Fe interlayers in montmorillonite was generally not temperature dependent, whereas the formation of such interlayers in vermiculite increased slightly with increasing temperature. These data may partially explain the formation of chloritic intergrades in soils as a function of type of minerals, kind of ions, and thermal variations.

Absorption of Pyrimidines, Purines, and Nucleosides by Co-, Ni-, Cu-, and Fe(III)-Montmorillonite (Clay-Organic Studies XIII)

Abstract: Absorptions of purine and pyrimidine derivatives by Co- and Ni- montmorillonite at pH Co ≫ Ca. Adenine, 7-methyladenine, hypoxanthine, and purine are strongly absorbed, 9-methyladenine, 6-chloropurine, and cytosine are weakly absorbed, and thymine and uracil are not absorbed. At pH 6 their absorptions decrease in the order Cu ≫ Ni > Co > Ca. Fe(III)-montmorillonite behaves quite differently from the other mont-morillonites studied. With purines and pyrimidines, there is strong absorption from pH 3 to pH 7–8; with the nucleosides, the absorption varies considerably with the compounds considered decreasing in the order adenosine > cytidine ≫ guanosine ≫ inosine.

Flint Clay and a Flint-Clay Facies

Abstract: Flint clay is denned as a sedimentary, microcrystalline to crystalline clay (rock) composed dominantly of kaolin, which breaks with a pronounced conchoidal fracture and resists slaking in water Additional ceramic (refractory) properties are implied, but not expressed, in the definition Flint clay first given recognition in the USA, has been observed on all continents; it will probably be found to be more abundant than its occurrences reported to date It occurs in rocks mainly Carboniferous or Cretaceous in age, and is invariably associated with plant- or coal-bearing measures The environment of deposition is commonly lowlying paludal, in basins in either clastic silicate rocks or in karstic carbonates It is inferred that parent illitic and/or kaolinitic clay colloids were transported into the swamps and there under-went further dialysis, alteration, and eventual crystallization in situ, producing a notably homogeneous kaolinite clay possessing interlocking crystallinity Some occurrences were further desilicated to high-alumina minerals, particularly to diaspore and boehmite Flint clay is interpreted as being an intermediate member of a so-called flint-clay facies which is a claystone sequence ranging from high-alumina minerals (or potentially so) formed on the highest part, structurally and/or topographically, of the depositional area, and grading down-structure and/or lower in elevation through flint clay to iliite-kaolinite plastic clay and thence to marine illitic shale, all being equivalent stratigraphically The geochemical reactions are depotassification of parent clay by substitution of K+ by H+, and desilication, especially where high-alumina minerals are formed

Heterogeneity of montmorillonite surface and its effect on the nature of hydroxy-aluminum interlayers

Abstract: A specimen montmorillonite (Arizona bentonite) was treated with hydroxy-aluminum solutions of various basicity. The cation exchange sites of this clay were found not to be homogeneous in their strength of retaining hydroxy-aluminum polymers; this strength varied from very weak, with which the A1 polymers were only loosely held, to very strong, with which stable interlayer AI-clay complexes were formed. When a large amount of clay was treated with a small amount of solution, the polymers were held only in positions of strong affinity; the polymers were difficult to extract with neutral salt solutions and did not change to crystalline AI(OH)3 during prolonged aging. When a small amount of clay was treated with a large amount of solution, the exchange sites were completely occu- pied by polymers; a portion of these polymers was easily extractable with neutral salt solutions and, during aging, changed to AI(OH)3. This contrast is significant in any attempt to compare results obtained under different experimental conditions and to correlate laboratory experimentation with the occurrence of gibbsite and interlayer AI-clay complexes in nature.

Low Frequency Dielectric Dispersion of Clay-Water-Electrolyte Systems

Abstract: —The dielectric properties of saturated kaolinite clay-water-electrolyte systems were determined over the frequency range of 30–105c/s. Very large dielectric constants are observed at low frequencies. Since the experimental data approach constant values at each end of this frequency spectrum, they can be described by a fairly well defined spectrum of relaxation times. The particle size and orientation, the type and amount of electrolyte, and temperature affect the low frequency dielectric increment and the average relaxtion time. Several physical processes, such as relaxtion due to dipolar rotational polarization, interfacial polarization, free space charge and bound ion polarization, are examined in an attempt to explain the observed data. It is concluded that there exists at present no theory to explain all the data, but the bound ion polarization mechanism appears to explain some of the results.

Morphology of Particles in Size-Fractionated Na- Montmorillonites

Abstract: Electron microscopy of particles in size fractions (0·5–1·0 μ, 0·1–0·5 μ, 0·05–0·1 μ and < 0·05 μ e.s.d.) obtained by centrifugation of Na-saturated montmorillonites from Wyoming (two samples); Chambers, Arizona; and Fayette County, Texas, has shown details of particle morphology. The finest fraction of each montmorillonite consists predominantly of very thin, separate flakes whereas all coarser fractions, totalling 80 per cent or more by weight of the samples studied, are composed of microaggregates. For all the samples, preferred orientation is best developed in specimens formed from flakes of the finest fractions. Microaggregates are stable in dilute suspension although they swell to give large interlayer spacings, but can be disrupted into smaller, thinner flakes by ultrasonic vibration. Differences in dispersion behavior between separate flakes and microaggregates are not due to differences in interlayer charge or chemical composition, which are very small between fractions of each sample, but are thought to be due to the interlocking of flakes in microaggregates during crystal growth, which prevents their complete separation in dilute suspension.

Hydroxyl Stretching Frequencies of Synthetic Ni-, Al-, and Mg-Hydroxy Interlayers in Expanding Clays*

Abstract: nterlayers were produced in montmorillonite, vermiculite and hectorite in aqueous suspensions by precipitation from metal chloride salt, by hydrolysis of metal amalgams, and by slow hydrolysis of metal acetate during refluxing. In several systems an external phase of bayerite, gibbsite, or brucite was also formed. A prominent high frequency OH stretching vibration is associated with the interlayer in montmorillonites with approximate frequencies of 3660 cm -1 with nickel interlayers, 3690 cm -1 with aluminium interlayers and 3710 cm -1 with magnesium interlayers. Pleochroism studies indicate transition moment of interlayer OH to be at a relatively high angle to the planar surface of the clay crystals. Aluminium interlayers show some evidence of an additional weak absorption in the lower frequency region of 3570-3600 cm -1. In differential studies the lower frequency absorption is more evident and is shown to be unaffected by orientation. Techniques involving balancing of water deformation bands in differential spectra and D20 exchange suggest that it is not a water band. D~O flushing to remove water leaves the low frequency interlayer OH band more prominent in hectorite where the clay crystal OH is at 3680 cm -~. Deuteration studies show that fushing with D20 at room temperature removes water, and heating at 100~ in D20 vapor exchanges interlayer OH but not the clay crystal OH. Study of the OD stretching of the systems with deuterated interlayers supports observations made in the OH stretching bands.

Glauconite Pellets: Similar X-Ray Patterns from Individual Pellets of Lobate and Vermiform Morphology

Abstract: Glauconite pellets of vermiform and lobate morphology occur together in Eocene geologic formations in Maryland. Morphologically, the vermiform pellets appear to be identical to those that have previously been called “altered biotite”. In thin sections these pellets do show a well-defined micaceous morphology with the layers running across the worm-like pellets. Some zones in these pellets appear to be “crystals” that are up to 30 × 70 μ and nearly rectangular in cross section. However, there are tiny cracks along cleavage planes within these “crystals”. Externally, the lobate pellets have many rounded lobes and are similar to one of the shapes that Burst has called free-form. In thin section under crossed nicols these pellets have a grainy appearance, indicating that the lobate pellets are composed of many small zones, each about 5–20 μ across. Within these zones the mineral glau-conite has a single orientation, but the zones are not lined up with each other to give the gross micaceous appearance that is associated with the vermiform pellets.

The use of clay in poultry feed

Abstract: Dietary clay supplements (bentonite and kaolinite) have been used as binding and lubri- cating agents in the production of pelleted feeds for chickens. The high-swelling and water absorbing capacity of some bentonites make them attractive dietrary additives for control of wet droppings in caged layers. In addition, experiments show that layers fed on these diets exhibit significant increases in body weight, egg size, and life expectancy even though their total caloric intake is less than that of the control group. Dietary kaolin improves caloric efficiency even more than bentonite but without ap- parent effect upon growth or carcass quality. Kaolins of smaller particle size are superior to those of larger size in improving caloric efficiency. The effective kaolins are estimated to be worth approxi- mately two calories of metabolizable energy per gram. The major beneficial effect appears to be due to a slowing down of the rate of feed passage through the intestinal tract. Possible uptake of trace elements required for optimum nutrition has not yet been evaluated.

Dickite and Kaolinite in Pennsylvanian Limestones of Southeastern Kansas

Abstract: Dickite and kaolinite are polymorphs of Al4(Si4O10)(OH)8. Dickite traditionally is regarded as hydrothermal, based on field and laboratory evidence. Dickite and kaolinite occur in cavities in phylloid algal limestones, in interstices of biocalcarenites and sandstones, and along joints, fractures, and stylolites, in Pennsylvanian rocks exposed throughout 9600 square miles of southeastern Kansas. The stratigraphic interval of approximately 1100 ft extends from the Fort Scott Limestone (Desmoinesian) through the Lecompton Limestone (Virgilian). The best crystallized dickites are found in porous algal limestones as pockets of glistening white powder composed of well developed pseudohexagonal plates up to 40 µ across. Very well crystallized kaolinites occur similarly, except the crystals are much smaller. Less well crystallized dickites and b-axis disordered kaolinites occur in less porous rocks. Variations in crystal size and morphological development are genetically significant. Dickite-kaolinite distribution is related to: (1) stratigraphic alternation of limestones and impervious shales; (2) gentle, westward regional dip; (3) thick, mound-like buildups of highly porous algal limestones, miles in length and width; (4) igneous intrusions (early Tertiary?) in Woodson and Wilson counties. Dickite is confined to an elliptical area 125 miles long northeast-southwest, extending 60 miles eastward from the intrusions. Dickite is associated preferentially with porous algal mounds. Kaolinite occurs in less porous rocks within the dickite area, and also is abundant well beyond. Heated groundwaters, possibly mixed with magmatic waters, moved readily up-dip and along strike outward from the intrusions through the conduit-like algal mounds; dickite was deposited from such solutions. Where water movement was restricted or where water had travelled tens of miles from the intrusions, water temperature fell below the limit for dickite crystallization, and kaolinite precipitated instead. Kansas dickite, unlike most other reported dickites, formed in rocks that were neither deeply buried nor extensively altered hydrothermally.

Hydrothermal Alteration of a Rhyolite Flow Breccia near San Luis Potosi, Mexico, to Refractory Kaolin

Abstract: A deposit of kaolin clay, the site of the General Zaragosa Mine, located about 50 km northwest of San Luis Potosi, S. L. P., Mexico, has produced more than 250,000 tons of refractory clay by room and pillar mining methods during the last 32 years. The clay was formed by hydrothermal argillation of part of a fault block of rhyolite flow-breccia and probably welded tuff, presumably lower Tertiary in age. A silica-rich gossan now exposed at the surface caps the clay deposit.

Retention of crude oil bases by clay-containing sandstone

Abstract: Retention of basic components of a crude oil by clay-containing reservoir sandstone was studied by flowing crude oil through cores and monitoring the concentration of bases in the effluent. Cores that were H-saturated, H-saturated then aged, and Na-saturated retained 0·82, 0·82, 0·70, and 0·20 meq base/100 g, respectively. Barium exchange capacity values were 0·86, 0·71, and 0·83 meq/100 g. Subsequent floods with water, toluene, and chloroform-acetone removed oil that had increasing concentrations of base and N, indicating that the basic fraction of crude oil was the most difficult fraction to extract from clay mineral surfaces. Retained bases were nitrogenous and the most tenaciously held bases had base/N ratios approaching unity.

Surface Conductivity and Dielectrical Properties of Montmorillonite Gels

Abstract: The surface conductivity of salt free montmoriUonite clay gels saturated with lithium, sodium, potassium and cesium has been studied. The theory of the behavior of heterogeneous dielec- trics adapted to systems having a surface charge density has been applied to the clay gels. From numerical calculations it became evident that the value of the depolarization factor may be extra- polated to 1 in the direction of the small axis of the platelet, meaning that the field action is zero in this direction. Along the long axis, however, the action is complete and the motion of the charge carriers is essentially tangential to the platelet. The values of the surface conductance are of an order of magnitude of l 0 -9 Mho. The investigation of the behavior of the water molecules has been carried out over a wide tem- perature range (145-320~ At temperatures below 273~ the conduction appears to be predomin- antly protonic; the counterions are considered to be disturbing elements in the water layer structures, thus creating a number of lattice defects able to transport the current. Above 273~ the conduction is essentially due to the adsorbed cations, their contribution starts during the phase change.

Quantitative Analysis of Naturally Occurring Multicomponent Mineral Systems by X-Ray Diffraction

Abstract: A theory for the quantitative analysis of multicomponent mineral systems by means of X-ray diffraction is presented. A linear interaction between mineral pairs is postulated. The theory is verified experimentally for bicomponent and tricomponent systems using a variety of sample preparation techniques including random powder mounts, suspensions sedimented onto glass slides, and pressed powder pellets. The minerals studied include quartz, fluorite, kaolinite, glauconite, illite, and montmorillonite. The determination of the linear interaction factors for mineral pairs is treated theoretically and experimentally. Emphasis is placed upon techniques that are applicable to naturally occurring mineral systems. Four approaches are presented for determining linear interaction coefficients for various types of such mineral systems. These approaches are applied to the experimental data and the results are compared. Results accurate within 2 per cent are commonly obtained. Experimental techniques are discussed and a qualitative and quantitative error analysis is pre- sented. It is shown that the indicated quantities present may not be particularly sensitive to the value of the linear interaction coefficient.

Infrared Study of the Orientation of Chlorobenzene Sorbed on Pyridinium-Montmorillonite

Abstract: The pyridinium-montmorillonite complex has the ability to sorb additional aromatic molecules between the layers. The neutral molecules occupy the vacant space produced by the change in orientation of the pyridinium ion from a parallel to a perpendicular position and with the N-H group directed toward the negative unit layer surface.

Cationic Diffusion in Clay Minerals:II. Orientation Effects*

Abstract: The effect of orientation of vermiculite particles on the diffusion of Na ion was measured by a tracer technique. The diffusion measurements were made on pellets prepared by pressing freezedried vermiculite in a cylindrical die and the diffusion coefficient evaluated by a thin-film boundary condition of Fick’s law. Because flakes of vermiculite were highly oriented under the pressing force, it was possible to prepare different angles of specimen orientation with respect to the surface where diffusion was initiated. Mathematical relationships of orientation angle, axial ratio of the platelets, and apparent diffusion coefficient were developed. The experimental results on the diffusion of Na ion in K-vermiculite of clay size gave apparent diffusion coefficients of 2·21 × 107cm2 sec−1 when the diffusion flux was parallel with the clay platelets and 0·45 × 10−7 cm2 sec “1 when the flux was perpendicular to the clay platelets. For the diffusion of Na ion into Na-vermiculite, apparent diffusion coefficients were obtained of 1·18 × 10−8cm2sec−1 when the diffusion flux was parallel with the clay platelets, and 0·18 × 10−8 cm2 sec−1 when the flux was perpendicular to the platelets. For K-vermiculite, the change in apparent diffusion coefficient is a simple one of particle geometry. The Na-vermiculite system exhibited more complicated behavior.

Measurement of Exchangeable Cations in Bentonites

Abstract: High swelling bentonites cannot be analyzed for exchangeable cations with exactly the same technique as most soils. To resolve varied techniques used in the past and to establish a reliable pro- cedure, the effects of sample size, the number of saturations, washes and extractions, and the volume of extracting solutions were determined on three high-swelling bentonites. Small samples must be used to insure complete extraction of exchangeable cations, and the 0.5 g weight was the best size of those tested. Most exchangeable cations were removed in three extractions with 25 or 33 ml volumes of ammonium acetate. More extractions could result in excessive solubiliza- tion of minerals. Centrifugal force must be sufficient to prevent loss of sample during decantation. This varied from 4500 to 7500 g for 10-20 rain, depending on particle size and sample dispersion. The proposed CEC method requires little time, but still compared closely with Frink's more extensive method and showed no significant difference between treatment means. The procedure was used to analyze high-swelling bentonites from fourteen locations in six Western States. Chemical properties changed within each deposit and with geographical location, but in general the bentonites contained high amounts of exchangeable Na, moderate amounts of exchangeable Ca and Mg, and low amounts of exchangeable K. Total exchangeable cations and CEC agreed well, demonstrating the reliability of the proposed method.

Mineralogical and geochemical study of clay mineral transformations in the sedimentary triassic jura basin (france)

Abstract: A detailed study of sediments from the Triassic of the French Jura shows that clay minerals vary continuously with the facies. Near the coasts of the Jura Sea, sediments consisted of sandy, continental detritus and the minerals are poorly crystallized. At the center of the basin, in what was a cation-rich chemical environment, they are well crystallized. A progressive mineralogical variation can be observed from degraded illite to well-crystallized chlorites passing through the intermediate stages of more-or-less regular mixed-layer structures. This variation is due to a true crystalline transformation. Similarly, chemical variations in clay minerals and whole-rock samples are related to the paleo- geography of the basin. The distribution of major and trace elements is a function of distance from the Jura Sea coastline and also a function of the mineralogical composition of the fine fraction. The most obvious relationships are: (1) An increase in the concentration of MgO and the percentage of ignition-loss water from the coast toward the deep sea; (2) A decrease in the concentration of SiO2, A1203, and TiO2 as well as that of trace elements such as vanadium, gallium, and cobalt from the coastal regions to the center of the basin; (3) A lack of statistically significant variations in the concentration of Fe203, Mn304, B, and Ni throughout the basin. The authors conclude that: ( 1 ) Transformations (aggradations) observed by means of X-ray diffrac- tion methods are in agreement with the chemical analyses; (2) Transformations are contemporaneous with the sedimentation; they are not diagenetic; (3) Clay minerals play an important role in the geochemical balance of sedimentary basins.

Electron microprobe study of kaolin

Abstract: Electron microprobe studies of kaolinite indicate that most of the Fe is evenly distributed throughout the kaolinite and must either be in the structure or occur as very small particles adsorbed on the surface. In addition to Ti the anatase impurities contain Fe and Mg. Fe, Mg, Mn, V, and K are present in biotite. It is necessary to concentrate the fine-grained mineral impurities in order to study them with the electron microprobe.

Some Results of the Study of Clay Minerals in the U.S.S.R.

Abstract: Clay mineral studies in the U.S.S.R., mainly since 1960, are summarized. Electron diffrac- tion techniques especially have been developed and used extensively. Methods have been developed for simultaneous recording of DTA curves and other properties. Polytypism of phyllosilicates has been studied intensively by Zvyagin and others. Mucfi new information on the structure and morphol- ogy of halloysites has been obtained by electron-optical methods. Other clay minerals extensively studied include allophanes, kaolinites, chlorites ("donbassite" is preferred to "sudoite" for diocta- hedral varieties), alushtite (or tosudite), monothermite, and various zinc-bearing clays. Much attention has been given to physico-chemical and colloid-chemical properties. The natural occurrence and alteration of clays and clay minerals are described in weathering and oxidation zones, in soils, and in Recent and Ancient sediments. Primary clay minerals of hydrothermal origin are described.

Structural charge site influence on the interlayer hydration of expandable three-sheet clay minerals

Abstract: Previous investigations have demonstrated the influences of interlayer cation composition, relative humidity, temperature, and magnitude of interlayer surface charge on the interlayer hydration of montmorillonites and vermiculites. It has been suggested that the sites of layer charge deficiencies may also have an influence upon the amount of hydration that can take place in the interlayers of expandable clay minerals. If the interlayer cation-to-layer bonds are considered as ideally electrostatic, the magnitude of the forces resisting expansion may be expressed as a form of Coulomb's law. If this effect is significant, expandable structures in which the charge-deficiency sites are predominantly in the tetrahedral sheet should have less pronounced swelling properties than should structures possessing charge deficiencies located primarily in the octahedral sheet. Three samples that differed in location of layer charge sites were selected for study. An important selection criterion was a non-correlation between tetrahedral charge sites and high surface-charge density, and between octahedral charge sites and low surface-charge density. The effects of differences in interlayer cation composition were eliminated by saturating portions of each sample with the same cations. Equilibrium (001) d values at controlled constant humidities were used as a measure of the relative degree of interlayer hydration. Although no correlation could be made between the degree of interlayer hydration and total surface-charge density, the investigation does not eliminate total surface-charge density as being significant to the swelling properties of three-sheet clay-mineral structures. The results do indicate a correlation between more intense expandability and predominance of charge deficiencies in the octa- hedral sheet. Conversely, less intense swelling behavior is associated with predominantly tetrahedral charge deficiencies.