Showing papers in "Clays and Clay Minerals in 1967"

Infrared absorption spectrometry in clay studies

Abstract: THE RELATIONSHIPS BETWEEN SPECTRUM AND STRUCTURE IN LAYER- SILICATES ARE REVIEWED, AND APPLIED IN THE STUDY OF STRUCTURAL CHANGES OCCURRING DURING THE HEATING OF MONTMORILLONITES UP TO DEHYDROXYLATION, AND THEIR SUBSEQUENT REHYDROXYLATION. INFORMATION GIVEN BY INFRARED SPECTROSCOPY ON THE BINDING OF WATER IN EXPANDING LAYER SILICATES IS PRESENTED, AND THE PHYSICAL AND CHEMICAL PROCESSES ASSOCIATED WITH ENTRY OF BASIC, NEUTRAL AND ACIDIC MOLECULES INTO THE INTERLAYER SPACE OF THESE MINERALS ARE ILLUSTRATED FOR AMMONIA, ETHYLAMINE, PYRIDINE, NITROBENZENE, AND BENZOIC ACID. PROBLEMS ASSOCIATED WITH THE STUDY OF SOIL CLAYS, WHICH ARE OFTEN COMPLEX MIXTURES INCLUDING POORLY ORDERED AND AMORPHOUS CONSTITUENTS, FREQUENTLY FIRMLY COMBINED WITH ORGANIC MATTER, ARE DISCUSSED. NEW EVIDENCE IS PRESENTED CONCERNING THE ENVIRONMENT OF THE TWO TYPES OF HYDROXYL GROUP IN BEIDELLITE. THE THERMAL STABILITIES OF NH SUB 4 AND LATTICE OH IN MONTMORILLONITE AND BEIDELLITE, AND THE PROPERTIES OF THEIR DEHYDROXYLATES, ARE CONTRASTED. THE NATURE OF THE COLLAPSED PHASE FORMED IN LI-, MG-, AND NH SUB 4 MONTMORILLONITE AT 300-500 C IS DISCUSSED. THE PRESENCE OF WEAK HYDROGEN BONDS BETWEEN LATTICE OXYGENS AND INTERLAYER WATER IS ESTABLISHED, ALTHOUGH IT IS SHOWN THAT THE STRENGTH OF HYDROGEN BONDS FORMED BETWEEN NH SUB 4 AND LATTICE OXYGENS IS DEPENDENT ON THE SITE OF SUBSTITUTION IN THE LAYER LATTICE. /AUTHOR/

Electron-Optical Study of Smectites*

Abstract: The combined use of electron microscopy and of selected area diffraction (SAD) has been applied to the study of montmorillonites from Wyoming and from Camp-Berteaux, of nontronite, and of hectorite. The study shows that only the elementary layers of the Wyoming montmorillonite and of the nontronite are single two-dimensional crystals. The elementary layers of the montmorillonite from Camp-Berteaux are formed by edge-to-edge associations of very small elements with mutual orientations of about 60° or multiples of 60°. The layers of hectorite are formed by edge-to-edge association of laths with fluctuations of orientation of the order of 10° rotation around adjoining edges. The SAD patterns of Wyoming montmorillonite show that the single layer plane symmetry group of this mineral is c1m1; nontronite layers belong to the symmetry group c2mm. The study of thick particles shows that in turbostratic smectites the layers are stacked with mutual rotations around the perpendicular to their plane. This mode of stacking explains the absence of hkl reflections. High resolution diffraction (HRD) patterns obtained with sample inclined to the electron beam show that only the structure of hectorite approaches the ideal model; nontronite and montmorillonite exhibit appreciable distortions with respect to the ideal model. HRD diagrams provide precise information for the refinement of the crystal structures of smectites

Properties of Vermiculites and Smectites: Expansion and Collapse

Abstract: Samples 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 A. 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 A. The K-saturated vermiculites tended to retain the collapsed lattice and exhibited diffraction maxima of 10–10·6 A with integral higher orders. Some hydration occurred as evidenced by peak asymmetry or the appearance of a small 14·3 A 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.

Alcohol-Water Interactions on Montmorillonite Surfaces. I. Ethanol

Abstract: Infrared spectroscopic, X-ray diffraction and gravimetric techniques were used so study the vapor phase adsorption of ethanol on homoionic Cu-, Al-, Ca,, Na-, and NH4-montmorillonite films. Equilibration of these films with ethanol vapor at a relative pressure of unity reduced the water content to less than 0.7% (300°C). As dehydration proceeded, the infrared absorption bands of the residual water were observed. Apparent differences between different cation saturations are reconciled by a consideration of the different types of ion-dipole interactions involved. Adsorption isotherms and X-ray diffraction results substantiated the interpretations of the infrared data. Prolonged evacuation did not remove all of the adsorbed ethanol as shown by spectroscopic and gravimetric techniques. Cu-, Al- and Ca-montmorillonite retained 4.5, 7.9, and 4.5 molecules per ion, respectively, while Na- and NH4-clays retained less than one molecule per cation. Ethanol loss occurred rapidly at 40% relative humidity except in the Cu-system where 70 hr were required for complete replacement. These differences indicate that the adsorption and retention of alcohol by montmorillonite is affected by the saturating cation and that alcohol and water compete for the same adsorption sites. Ion-dipole type interactions should thus be considered in adsorption mechanisms of alcohol on montmorillonite.

Interstratification in Vermiculite

Abstract: Vermiculite (Libby, Mont.) was ground in a Waring blender in a 1 m NaCl solution and, after removal of excess electrolyte, the clay fraction was separated by sedimentation. The clay was predominantly vermiculite: X-ray diffraction patterns of Ca-saturated and oriented specimens showed an intense and sharp 15 A and a weak 25 A diffraction maxima and their integral orders. The intensity of the 25 A reflection, attributed to regularly interstratified layers of vermiculite (15 A) and mica (10 A), was less than 20% of the 15 A peak. Additions of varying amounts of potassium or cesium, ranging from 10% to 100% of exchange capacity, to Ca-saturated clay showed that the collapse of the vermiculite lattice proceeds through a 1:1 regular interstratification of a 15 A and a 10 A lattice. Successive additions increased the 25 A diffraction peak at the expense of the 15 A reflection until the entire sample was interstratified. Further additions of K (or Cs) reduced the intensity of the 25 A reflection and produced a 10 A reflection until the entire sample was collapsed to 10 A and no 25 A reflection was recorded. These observations point out that under certain environmental conditions, the diagenetic formation of micas from vermiculite may proceed through an interstratification of the two in a manner analogous to weathering of biotite to vermiculite through an interstratified stage. One-dimensional Fourier synthesis from the intensities of the 00l diffraction maxima of the interstratified mixture was carried out. In addition, a mechanism for the formation of the interstratified mixture was postulated: the replacement of Ca by K (or Cs) in one layer reduces the effective negative charge on the adjacent layer. Consequently, the K cannot replace the Ca in this but replaces the Ca in the next layer forming the interstratified mixture.

Polyelectrolyte Reinforced Aerogels of Clays—Application as Chromatographic Adsorbents

Abstract: Aerogels of clays can be prepared by freeze-drying of clay water gels. The mechanical strength of the aerogels is improved by the addition of water-soluble polyelectrolytes to the hydrogels. The porosity of the powdered aerogels can be adapted to the requirements for adsorbents in gas chromatography by compounding the hydrogels with suitable amounts of polyelectrolytes. Simultaneously, the surface of the clay may be modified by adsorption of polar or cationic organic compounds in order to achieve specific chromatographic separations. Because of the toughness of the clay-polyelectrolyte aerogels, they can be rolled out to thin sheets which may be applied as chromatographic papers.

Particle Arrangements in Kaolin

Abstract: An ambiguity in interpretation of electron micrographs of replicas of fracture surfaces of dry clay samples is illustrated, and a method of making ultra-thin sections described. Micrographs of ultra-thin sections of remoulded, consolidated, and sheared kaolin specimens are shown. In unconsolidated specimens random arrangements of particles, or of small groups of particles, were found. In failure zones, in sheared samples, the preferred orientation was parallel to the zone, with, in some cases, a subsidiary zone in which particles were inclined to the main zone. Interparticle contacts were mainly edge-to-edge or face-to-face.

Influence of Exchange Ions on the b-Dimensions of Dioctahedral Vermiculite

Abstract: The 1–5 µ size fractions of different ground muscovites were treated for a 30-day period for K+ removal with a pH 75 solution containing sodium tetraphenylboron The initial K+ contents ranged from 211 to 219 me/100 g After the extraction period, the final K contents ranged from 21 to 37 me/100 g The apparent structural charge on the expanded material decreased to values ranging from 156 to 184 me/100 g, which are within the charge range for natural vermiculites The b-dimensions of these laboratory-produced vermiculites were found to vary with the exchange ion and with the hydration state of the ion For hydrated samples, saturation with Cs+, Li+, and Mg2+ ions increased the observed b-dimension in comparison to that of the corresponding parent mica, whereas saturation with Sr2+ and La3+ ions had little effect on b After dehydration at 350°C, only Cs+-saturated samples had a b-dimension greater than that of the parent mica The observed b-dimension for the dehydrated samples was found to be a direct function of the crystal radius of the interlayer ion Apparently, as the ion dehydrates, the surface oxygen triads rotate until some of the oxygens “lock” onto the ion, limiting the minimum b-dimension Before dehydration, however, the water of hydration in the interlayer region is evidently held with sufficient energy to limit rotations of the oxygen triads that give rise to a decrease in b When Li+ and Mg2+ ions occupy the interlayer region, their water network apparently even produces a slight increase in the observed b-dimension

Visible Changes in Macro Mica Particles That Occur with Potassium Depletion

Abstract: Mica particles approximately 10 or 25 mm square and 0.5 mm thick were placed in NaCl-NaTPB solutions to make visual observations of the changes that occur in micas when the interlayer K is replaced by Na. Samples of muscovite, biotite, phlogopite, lepidolite, and lepidomelane were used, and the effects of different degradation periods were photographed. An increase in the thickness of the particles due to basal planes splitting apart was observed with all micas. This exfoliation released interlayer K and in some cases caused the particles to cleave into separate flakes. Lepidomelane particles remained intact despite a 20-fold increase in thickness in 7 days. Even muscovite and lepidolite exfoliated and cleaved, but much longer degradation periods were needed. There was a distinct change in the color of the dark biotite, phlogopite and lepidomelane particles when K was removed. Therefore, the initial stages of K depletion at holes, scratches, and edges of the particles were easily followed. As the degradation of the mica particles progressed, however, the color of the mica became a less reliable index of the stage of K depletion. Visual evidence of K depletion at the edges of particles was also obtained with muscovite, but not with lepidolite. Transverse sections of 25-mm particles of K-depleted biotite were photographed to show the edge expansion that occurred when interlayer K was replaced by Na.

Size and Shape of Montmorillonite Crystallites

Abstract: Spray drying dilute suspensions of bentonitic montmorillonite produces a powder that shows totally random orientation of the crystallites within a sample large enough to diffract X-rays. The powder is collected by an electrostatic precipitator and can be handled in the normal mounting processes without introducing preferred orientation. Electron micrographs show this powder to be composed on a small scale of thin, crumpled, and rolled films. The extremely small montmorillonite crystallites that make up the film are oriented with [001] directions perpendicular to the film surface. Orientation within the plane of the film is random as shown by selected area electron diffraction. Crumpling and rolling of the film is sufficient to make the orientation of [001] directions random in three dimensions in a large sample when X-ray diffraction is registered. The X-ray diffraction patterns all show diffraction maxima (both hk and 00l), and their relative intensities with respect to each other can be determined. The line broadening of the 06 and the 003 peaks was studied. The average crystallite size as calculated from the line broadening varied from six to eleven unit layers thick for four bentonitic montmorillonites. The average lateral dimension of crystallites varied from 140 A to 250 A. Ratios of lateral dimensions to thickness varied from 2.3 to 3.4.

Interlamellar Reactions of Tetracalcium Aluminate Hydrates with Water and Organic Compounds

Abstract: Tetracalcium aluminate hydrates are the first example of layer-structured crystals containing neutral sheets, which are highly capable of interlamellar adsorption of water and neutral organic compounds. In this respect tetracalcium aluminate hydrates present new aspects of the phenomenon of swelling, and bring about the challenge of comparison with the frequently examined clay-organic compounds. This report is concerned with the probable monolayer structure of tetracalcium aluminate hydrate which forms five hydration stages. A summary concerning configuration and properties of adsorption complexes with approximately 500 selected organic substances follows. As far as these substances are homologues of certain functional groups, the change of basal distances depends upon the number of C-atoms. Aside from pure organic compounds, one can also form interlamellar complexes with a mixture of such compounds. Here again a rule of proportion between the number of C-atoms and the basal distance becomes evident. Another variant is the mixed interlamellar complexing of water with organic compounds and the re- and de-hydration reactions of these products. The report discusses the bonding conditions of various functional organic groups to the inorganic lattice. Furthermore, a series of homopolar organic derivatives of the tetracalcium aluminate hydrates can be produced. As is known, the existence of such compounds of clay minerals is a subject of dispute.

Authigenic Silicates Formed from Basaltic Glass by More than 60 Million Years’ Contact with Sea Water, Sylvania Guyot, Marshall Islands

Abstract: Dredge haul MP43A, from a depth of 6180–10,860 ft on Sylvania Guyot, the companion seamount to Bikini Island, yielded large blocks of yellow buff-colored rock consisting of clay, opal, phillipsite, and veins of phosphatized foraminifera of basal Eocene age, suggesting more than 60 million years' exposure to sea water. These freshly broken blocks were partially covered with crusts of hydrated manganese and iron oxides. Occasional incompletely altered fragments indicate that the original volcanic rock was basaltic glass in a tuff breccia. The alteration products consist of: (1) water-clear phillipsite, (2) opal spherules which appear to have formed as linings of vesicles in the original glass, (3) a buff-colored, disordered, chloritie, mixed layer clay consisting of montmorillonite with interlayer ferric hydroxide. The typical basaltic glass, weathered in the oceanic environment for much shorter periods of time, is converted to montmorillonite and phillipsite. The principal effect on the phillipsite of long exposure to sea water is etching of the crystal surfaces indicating non-equilibrium with sea water. The effect of the environment on montmorillonite is iron chloritization. Addition of iron occurs on a layer-by-layer basis, suggesting that hydroxy-iron polymers occur in sea water. Iron chloritization reduces the CEC of the MP43A montmorillonite by approximately one-third.

Biotites Intermediate Between Dioctahedral and Trioctahedral Micas

Abstract: Orange-yellow detrital flakes of biotite are common carriers of potassium and trace elements in soils and clays. Because the flakes differ in degree of alteration and may be derived from different sources, it is difficult to obtain homogeneous material for studies of their physical and chemical properties that may be compared with the original mica. A similar orange-yellow altered biotite occurs with fresh biotites in alkalie rocks of a nepheline deposit. The fresh and altered biotites were separated for chemical and minoralogical studies of the effects of weathering on biotite in its parent rock. The common iron-rich biotites with octahedral occupancy between 5.5 and 5.8 alter to bright orange-yellow biotites with octahedral occupancy approaching five. These biotites, intermediate between the trioctahedral and dioctahedral micas, form as a result of oxidation during the process of their alteration to chlorite—vermiculite. Biotites with octahedral occupancy approaching five were prepared experimentally by heating a natural biotite that contained high ferrous iron. The main differences between the natural and laboratory oxidized biotites are: the naturally oxidized micas lose 30% of the original potassium, adsorb about 2 wt.% water, and apparently gain about 25% hydroxyl, whereas laboratory oxidized micas retain potassium and lose hydroxyl and argon. The oxidized micas retain the crystal structure of the original mica.

Order of Mixed-Layering in Illite/Montmorillonites

Abstract: A number of otherwise poorly understood compositional-structural relationships in mixed-layer illite/montmorillonites appear to be explained by ordered interlayering of 2:1 units. The ordering appears to be between high and low charge 2:1 units. The relationship between per cent expandable layers and mean lattice charge in natural materials shows a scatter that is nicely bracketed by hypothetical curves constructed assuming random or completely ordered interlayering for several types of 2:1 charge distribution. Natural samples with 30–50% expandable layers plotting near the “ordered” curves have diffraction peaks at 25 A for two water layers in the expandable layers and 27 A with two glycol layers; samples plotting near the “random” curves do not have these peaks and have poorly developed 001/001 reflections. Some tentative conclusions are: (1) illites are virtually non-expandable at lattice charges significantly less than that of ideal mica because of ordering of high-low charge 2:1 units, (2) illites and mixed-layer illite/montmorillonites with the same mean lattice charge show a range of expandability because of varying degrees of ordering, (3) the highly variable CEC of samples with the same expandability also results from a varying degree of ordering. An interesting petrological implication results when it is realized that a sample with a given bulk composition can have a wide range of expandability, depending on ordering. Low expandability, achieved by ordering, should be promoted by formation at high pressures. Glauconites, known to form largely at the time of sedimentation, appear to be dominantly randomly interstratified; illites and illite/montmorillonites, which may form on deep burial of argillaceous sediments, are dominantly ordered.

X-Ray Study of Interactions between Montmorillonite Platelets

Abstract: Small angle X-ray scattering curves have been obtained for a series of Na Wyoming Bentonite clay samples containing 10% clay by weight and NaPO3 in concentrations ranging from 0 to 100 meq/1. From the scattering data, the relative probability of spacings between parallel clay platelets was computed. For the sample containing no NaPO3, the probability distribution showed a relatively broad maximum at an interparticle spacing of about 180A. As the concentration of NaPO3 increased, the maximum became sharper and occurred for smaller interparticle distances. At NaPO3 concentrations between 25 and 100 meq/1, the position d of the maximum was given approximately by the equation d = 21 + 18.4c-1/2, where d is in angstroms, and c is the NaPOs concentration in eq/1. The similarity of this relation to the dependence of d on the concentration of NaCl (Norrish and Rausell-Colom, 1963; Norrish, 1954) suggests that the interparticle spacing depends primarily on the sodium ion concentration and not on the concentration of the anion. The value of d appears to be independent of whether the gel was prepared by the method of Norrish and Rausell-Colom, in which a dried flake was allowed to come to equilibrium with an electrolyte solution, or whether, as in this investigation, the gel was obtained by centrifuging a dilute suspension. Since the Na ions act to reduce the double-layer repulsion between platelets, while the anions tend to be adsorbed on the platelet edges and thus reduce the edge-to-face linkages (H. van Olphen, 1962), the value of the most probable interparticle distance appears to be determined primarily by the magnitude of the double-layer repulsion, even though other properties of the clay gels, such as the rheological behavior, are governed mainly by edge-to-face attractions.

Orienting Internal Standard Method for Clay Mineral X-Ray Analysis

Abstract: Use of a platy internal standard that will orient to the same degree as clay minerals preserves the relative diffraction intensities between the basal reflections from the platy components, regardless of degree of orientation. The method is illustrated with basic zinc chloride and pyrophyllite as the internal standards for quantitative clay mineral analysis in the systems kaolinite-1Md illite and 2 M1 muscovite-montmorillonite. Ulite does not orient to the same degree as kaolinite at high illite concentrations. In such nonlinear systems empirical working curves are more reliable than fixed ratios of the scattering powers of the clay minerals present. Random interstratification of 10/15.4A layers causes a minimum in 001/001 peak height at about 33% of the 15.4A component. Peak width varies in a similar but inverse pattern, so that the integrated intensity increases in a smooth curve from muscovite to montmorillonite. The major error in application of this quantitative method arises from uncertainty as to the correct allocation of peak areas in cases of overlap of the mixed-layer peak with those of discrete 10 A and 14 A clays also present.

X-ray Diffraction Band Profiles of Montmorillonite—Influence of Hydration and of the Exchangeable Cations

Abstract: Previous studies of diffraction band profiles of montmorillonite are extended to the 13, 20 band which, for reasons discussed, is more sensitive to structural details than the diffraction bands considered previously. Hydration of Na-montmorillonite produces appreciable sharpening of this band, indicating, contrary to previous results, that the water layers have at least a partially ordered arrangement. For Cs-montmorillonite, the single water layer hydrate shows only a small sharpening of the band profile, possibly attributable to the water layer, but which clearly indicates that the Cs ions cannot be significantly displaced from their positions in the anhydrous material. For Ba-montmorillonite, the two-layer hydrate shows a small broadening of the diffraction band, which is possibly the result of a partial ordering of the water layers together with a movement of the Ba ions away from the hexagonal holes.

Sorption of Water at High Temperatures on Certain Clay Mineral Surfaces. Correlation with Lattice Fluoride

Abstract: The sorption of water, at 490°C and ca. 23–24 torr, on clay mineral surfaces has been studied using thermogravimetry and infrared absorption spectroscopy. Results from a series of synthetic hectorites, with and without lattice fluoride (see Granquist and Pollack, 1960), point to the presence of F− in the clay lattice as an important condition for the sorption. Similar studies on natural hectorite and montmorillonite, synthetic interstratified montmorillonite/mica with and without fluoride, and Al2F6 support this interpretation of the role of the F− ion and show that dioctahedral 2:1 clays sorb more water at 490°C than do trioctahedral 2:1 clays. The infrared spectra demonstrate that the sorbed water is for the most part hydrogen-bonded to the surface.

Surface Properties and Texture of Chrysotiles

Abstract: Nitrogen surface areas and pore-size distribution curves of various chrysotiles have been measured using a continuous flow method. A model founded on a hexagonal close packing of fibers has been adjusted to fit the frequency distribution curve of the fiber outside diameters obtained from electron micrographs. From this model, theoretical distribution functions of the surface area versus the pore diameter were computed and compared to the experimental data. For one fiber only (i.e. Coalinga chrysotile), the good agreement between the computed and experimental data allows one to conclude that the external pores (between the fibers) and the internal pores (within the fibers) are free from any amorphous material. For the other studied chrysotiles, the degree of filling of the pore system by amorphous materials was always higher than 50%. Under these conditions, hydration water cannot be removed unless the samples are pretreated in the 300°–400°C temperature range. On the contrary, water is driven off from the “clean” Coalinga fibers at temperatures lower than 100°C. Surface area measurements derived from water-adsorption isotherms correspond to those obtained with nitrogen after the hydration water has been removed.

Electron Diffraction and Micrographic Study of the High-Temperature Changes in Illite and Montmorillonite Under Continuous Heating Conditions

Abstract: Transmission and diffraction electron micrographs were made of illite and montmorillonite to study the changes that take place as the clays were heated continuously to 1200°C. In both of the clay minerals studied, expulsion of a highly fluid material occurred subsequent to dehydroxylation and prior to the development of the first-formed high temperature phases. It was hypothesized that this material represented the expulsion of constituents in the clay in excess of those needed for the formation of the first high-temperature phase. Electron diffraction indicates that the high-temperature phases that formed all developed with some preferential orientation, and were strongly influenced in their development by the structure of the original clay.

Lateral Gradation of Chabazite to Herschelite in the San Simon Basin

Abstract: The first occurrence of herschelite in the United States has been discovered in bedded Tertiary lake deposits in the San Simon basin, 7 miles northeast of Bowie, Arizona. From all analyses reported, the San Simon herschelite ranks as the sodium end member in the herschelite-chabazite series. Its chemical formula is $$\left( {0.91N{a_2},\,0.05{K_2},\,0.04Ca} \right)O\, \cdot \,A{l_2}{O_3}\, \cdot \,6.4Si{O_2}\, \cdot \,7.6{H_2}O$$ and grades laterally northward to the edge of the basin to an intermediate composition of (0.38Na2, 0.01K2, 0.61Ca)O · Al2O3 · 6.68SiO2 · 8.4H2O. The crystals occur as radiating aggregates and spherulites which range in size from 25 to 50 microns. The mean index of refraction varies from 1.473 for the sodium end member herschelite to 1.481 for the intermediate sodium-calcium chabazite. The X-ray diffraction data of the varieties are similar, but there is a direct correlation of peak shifts with composition. The chabazites were formed by the alteration of bedded pyroclastics. In the center of the basin, herschelite occurs as thin layers interbedded with thin layers of analcime, erionite, and clinoptilolite, which are underlain by a massive bed up to 2 ft thick of herschelite, erionite, and clinoptilolite. Bentonite underlies the zeolitized beds. Halite, thenardite, and iron oxides occur in amounts up to 10 weight per cent with the herschelite. Northward the beds of analcime and bentonite pinch out and the halite, thenardite, and iron oxide contents decrease in the chabazite layer. Near the edge of the basin, the chabazite bed is 6–8 in. thick and is overlain by a massive bed of erionite, chabazite, and clinoptilolite and underlain by a quartz feldspar silt. Tertiary andesites and Quarternary basalts rim the basin. The silica to alumina ratio of all the zeolites is the same as andesitic glass. The gradation in the exchangeable cations in the chabazite—herschelite series either reflects the solution chemistry during crystallization or is a result of subsequent ion exchange by descending salt solutions.

Electrokinetic Effects in Kaolin-Water Systems. I. The Measurement of Electrophoretic Mobility

Abstract: A new apparatus for the measurement of electrophoretic mobilities of particles in concentrated suspensions has been developed. The usual techniques for the study of electrophoretic mobility, such as the microelectrophoretic method and the moving-boundary method, arc in general not applicable to suspensions more concentrated than about 1 % by volume of dispersed phase, nor are they readily applied to suspensions of particles having an appreciable sedimentation velocity. The new apparatus, which employs an improved design of mass-transport cell, has been used to study suspensions containing up to 50% by volume of dispersed phase. Gravitational effects are eliminated by continuous rotation of the cell during a mobility determination.

The Influence of Alkaline Solutions on the Alteration of the Clay Minerals

Abstract: The influence of an alkaline environment on clay mineral alterations in the laboratory was studied by means of one-dimensional structural analyses. Samples of illite, illite-mixed-layered material, kaolinite, and two montmorillonites (smectites) were treated with NH4OH solutions of pH 8.5, 9.5, 10.5, 11.5, and 12.5 for 6, 12, 24, 48, 72, and 96 hr at 60°C.

Clay mineralogy of andesite saprolite

Abstract: Clay mineral associations in saprolite of two andesites from the Cascade Range of northeastern California were determined. Sesquioxidic allophane with a high CEC delta value dominates the clay fraction of the least weathered saprolite in each series (47% and 37% in hypersthene andesite and olivine andesite saprolites, respectively). With further weathering, the content of amorphous clay remains high (over 30% in all cases) but the CEC delta value of the clay drops markedly. The amorphous material in the more weathered saprolite has the properties of halloysitic allophane. Halloysite, present in all saprolites, is highest in concentration (over 30%) in the more strongly weathered members of each of the saprolite series. Formation of sesquioxidic allophane during early stages of weathering and its transformation to halloysitic allophane and halloysite during later stages of weathering are supported by X-ray diffraction, electron microscopic, DTA, elemental analysis, and CEC delta value data.

Formation of Zeolite Type A from Halloysite and Allophane

Abstract: h ' Is well k n o w n t h a t kaol ini te a n d hal loys i te change in to h y d r o x y sodal i te by t r e a t m e n t wi th sodi tun hydrox ide . I t is also k n o w n t h a t s o d i u m zeolite type A can be fo rmed f rom kaolini te, af ter i t h a s been h e a t t r e a t e d into me takao l in , or g r o u n d in to noncrystal l ine mater ia l . F r o m such facts it is p r e sumab le t h a t t he p robab i l i ty of f o rma t ion of zeolite type A f rom a kaol in minera l is closely re la ted to the e rys ta l l in i ty of t he originM mineral . F r o m such a considerat ion, in the p resen t e x p e r i m e n t s a l lophane a n d some kaol in minera l s w i t h different degrees of c rys ta l l in i ty were used as s t a r t i ng mater ia l s . S tar t ing samples were Mesa Al t a kaolini te, Kibush i -c lay , W a g o n Whee l Gap hal loysi te , Ina-kaol in , a n d I i j ima a l lophane. Of these s t a r t ing samples , Mesa A l t a kaolini te is a species w i th the h ighes t degree of e rys ta l l in i ty a m o n g t he kaol in minera ls , a n d K ibush i clay h a s a lower degree of e rys ta l l in i ty s imilar to f i re-day. Ina-kao l in is a ha l loys i te w i th the lowest degree of e rys ta l l in i ty of all t h e kaol in minera ls , a n d it belongs to the a l l o p h a n e hal loysi te series. I i j ima a l lophane is the m o s t typica l soi l -a l lophane found in J a p a n . To examine t he effect o f c rys ta l l in i ty on t he s t ruc tu ra l change of kaol in mine ra l s b y t r e a t m e n t wi th s o d i u m hydrox ide , the following expe r imen t s were made . For each run , 50 g of a s t a r t ing sample were added to 250 ml of 4~r N a O H aq solut ion, and t r e a t ed for 3 h r a t t he boiling po in t u n d e r agi ta t ion . F r o m the X r a y diffract ion resul ts , i t is found t h a t kaolini te a n d hal loys i te change to h y d r o x y sodali te dur ing th i s t r e a t m e n t , a n d t h a t sod ium zeolite t ype A can be recognized in the p roduc t s f rom poor ly crys ta l l ized hal loysi te and a l lophane. Next , to inves t iga te t he m e c h a n i s m of t he fo rma t ion of zeolite t y p e A f rom Ina~ kaolin b y t r e a t m e n t w i t h N a O H in fu r the r detail , t h e correla t ion be tween t he zeolite eon~ent of the p roduc t a n d the t r e a t m e n t t i me in t he process of N a O H t r e a t m e n t was obtained. I n th i s expe r imen t , the a m o u n t of N a O H used was the convers ion va lue corresponding to 110 m o l t o of lga20 requi red for t he fo rma t ion of zeolite type A. A n d the quan t i t a t i ve analys is of the zeolite con ten t was m e a s u r e d b y the X r a y dif f ract ion m e t h o d wi th fluorite as t he in terna l s t anda rd . F r o m these resul ts , i t is found (1) t h a t the zeolite con ten t of t he p roduc t genera l ly increases w i th the progress of t r e a t m e n t a t a cer ta in t empera tu re , b u t af ter reaching a cer ta in po in t of the t r e a t m e n t t ime t h e apparen t zeolite con ten t decreases, and (2) t h a t zeolite type A wi th a 100% p u r i t y is obta ined b y reac t ion for 16-24 h r a t 70~ I n th is react ion, an induc t ion per iod is observable, and t he l eng t h of th i s per iod depends on t he t r e a t m e n t t empera tu re . Th i s induct ion period cor responds to the following two p h e n o m e n a , t h a t is, (1) kaol in minerM reacts to lgaOH, and consequen t ly the original kaol in s t ruc tu re is b roken and becomes amorphous and (2) t he nuc leus of zeolite t ype A fo rms in th is a m o r p h o u s s ta te .

Electron-Optical Study of Alteration to Smectite in the Cheto Clay Deposit

Abstract: Volcanic ash of latitic composition in the Pliocene Bidahochi formation of northeastern Arizona has been altered in place to smectite clay. The Cheto clay, a 4-ft thick bed of high-quality activable smectite, offers an excellent opportunity for electron-optical study of the alteration processes in volcanic glass shards, spherulites, and aggregates in the tuff. No completely unaltered tuff remains in the exposed bed, but transitional materials showing progressive alteration from vitric tuff toward massive smectite have been collected and examined petrographically, electron-optically, and by X-ray diffraction. The partly altered tuff shows several clearly identified structures relatable to the fresh material: spherical to subspherical spherulites, conchoidally fractured subtriangular to irregular vitric shards dominated by smoothly curved pitted surfaces, massive essentially structureless glass, and columnar fused aggregates which appear interstitial to the shards. Upon alteration these aggregates display an irregular comb-like structure from a planar base in cross-section, and a hackly polygonal to random texture normal to the comb structures. X-ray diffraction reveals only montmorillonite in the materials examined, although minor quartz and plagioclase feldspar have been reported elsewhere in the partially altered ash. Argillization of the vitric tuff involves several phenomena: (1) the development of layering or banding in the glass; (2) the development of a braided surface aspect perhaps related to banding; (3) the inception of arcuate subparallel lineations on internal curved surfaces of the glass; (4) the growth of pseudohexagonal, weakly curled flakes whose boundaries appear threadlike on glass surfaces, and (5) the growth of grossly hexagonal matted granular networks in completely altered glass. Bladed, comb-like smectite develops along interfaces between glass and more resistant shards and from fused columnar aggregates in the original material. The mechanism appears to be one of essentially pervasive nucleation and growth of smectite in the devitrifying glass with the early development of preferred orientation of individual smectite crystallites. This orientation, manifested in layering and braiding, may reflect simple response to the space problem or response to cryptostruetures and polymerization in the original glass. Relic structures relatable to the unaltered vitric tuff are not obliterated and can be discerned even in the completely altered ash.

Compositional Variation of a Vermiculite as Related to Particle Size

Abstract: A vermiculite regolith sample from Llano, County, Texas, was divided into 16–32, 8–16, 4–8, 2–4, 1–2, ½–1, ¼–½, 1 10–¼, and 5 100–1 10 micron equivalent spherical diameter size-classes. A well-crystallized vermiculite found in association with the regolith was ground to −400 mesh. The samples were analyzed by X-ray diffractometry and differential thermal analysis, and cation exchange capacity measurements were made for selected size fractions. Chemical analyses by X-ray fluorescence revealed a systematic increase in silicon with decreasing particle size. An increase in the iron content and a decrease in magnesium were also directly correlated to a decrease in the crystallite size. Aluminum content was constant throughout the range of particle sizes. X-ray analyses showed that the coarser particles were trioctahedral, whereas the smaller crystallites were dioctahedral. These data were supported by recast formulae based on the chemical analyses. The recast formulae were substantiated by DTA and cation exchange capacity data as being reasonable approximations of actual formulae. These observations are interpreted as an expression of chemical alteration that clay minerals may undergo in an aqueous environment. The crystallographic, cation exchange capacity, DTA, and swelling properties are a function of the chemical composition of the crystallites. Chemical composition of the crystallites is shown to be directly correlated to particle size.

The Influence of Pressure on the Electrical Resistivity of Clay-Water Systems

Abstract: The influence of pressure on the electrical resistivity of clay-water systems was investigated and found to reflect the abnormal nature of adsorbed water. The resistivity of montmorillonite—water systems varied with pressure in a manner similar to a dilute salt solution at pressures above 7000 psi. At pressures below this, abnormal pressure- resistivity relations resulted which were attributed to the presence of abnormal water associated with clay mineral surfaces. The pressure-induced breakdown of the abnormal water associated with montmorillonites was found to occur in abrupt stages as indicated by anomalies in the pressure—resistivity curves.

Clay Mineral Formation in Mud Pots, Yellowstone Park, Wyoming

Abstract: Kaolinitic, montmorillonitic, illitic, and mixed-layer clay minerals are found in mud springs and mud pots of Yellowstone Park. A sequence of alteration is proposed as Phase I, alteration of bedrock and sediments by hot spring waters to produce three-layer clay minerals (including mixed layer species) and kaolinite-group minerals; Phase II, further alteration to produce a mud composed predominantly of kaolinite and some form of silica.

Mineral Analysis of Natural Zeolite Deposits

Abstract: Natural zeolites in altered volcanic tuff beds occurring in southeastern Oregon and north central Nevada show layers of mordenite, clinoptilolite, and erionite as principal minerals with occasional occurrence of phillipsite and chabazite. The sequence mordenite (phillipsite), clinoptilolite, erionite (chabazite) seems to be typical of the deposits investigated. This order is concurrent with a decreasing Si/Al ratio in the zeolite composition. The mordenitic layers at the base of a sequence usually show a considerable amount of non-zeolitie minerals such as quartz, feldspar, illite, fluorite, and calcite. The layers of clinoptilolite and erionite, on the other hand, contain relatively pure zeolite. At some localities, the erionite layers are not completely altered and contain unaltered volcanic glass. Powder X-ray diffraction, electron microscopy, and electron diffraction methods have been used for analyzing the zeolitic deposits. Mineral separation techniques not only provided purified samples of zeolites for experiments on their chemical and physical properties, but also facilitated the determination of the nature and amounts of the various impurities present.