bluuebunny/crossref_metadata_2025 huggingface dataset:
Mineralogy, O18/O16, and D/H Ratios of Clay-Rich Sediments from Deep Sea Drilling Project Site 180, Aleutian Trench
Authors: Eslinger Eric V. , Hsueh-Wen Yeh
Published: August 2006

Mineralogy, O18/O16, and D/H ratios have been determined in five size fractions (<0.1, 0.1–0.5, 0.5–1.0, 1.0–2.0, and >2.0µm) of seven samples taken from 500 m of Pleistocene deep-sea sediments cored at Deep Sea Drilling Project Site 180 in the Aleutian Trench. The depositional age of the samples spans the last 300,000 years; the samples have been interpreted by others to be continental detritus weathered from a mixed igneous, metamorphic, and sedimentary source area and then deposited by ice-rafting and turbidity currents. The minerals present are quartz, feldspar, illite, chlorite and/or non-expandable vermiculite, and expandable vermiculite and/or mixed-layer illite/expandable vermiculite. The relative amounts of quartz, feldspar, and total clay vary with particle size, but are nearly constant from sample to sample for a given particle size. δO18 is values of the four coarser size fractions range from +9.7 to +12.0‰ with variations attributable to changes in quartz/feldspar and clay/(quartz + feldspar) abundances. Values of δO18 for the expandable vermiculite-rich <0.1-µm size fraction range from +12.1 to +16.3‰ which indicates some oxygen isotope exchange at surface temperatures between meteoric waters and the parent rock during vermiculite formation. Values of δD range from −46 to −74‰ with variations attributable to changes in amounts of different clay minerals present. There is no mineralogic or isotopic evidence of post-depositional reactions in the coarser size fractions, but a general change in δD of the vermiculite-rich, <0.1-µm size fraction from about −50‰ to about −70‰ with increasing depth may be due either to post-depositional isotopic exchange or to climatic changes in the terrestrial weathering environment.
Kinetics of Glass Dissolution and Zeolite Formation under Hydrothermal Conditions
Authors: Hawkins Daniel B.
Published: August 2006

After a temperature-dependent period when little dissolution occurs, the dissolution of rhyolitic glass can be described by dC/dt = k(Cs − C), where Cs is the concentration of dissolved silica at saturation, C is the instantaneous silica concentration, and k is a rate constant equal to 1.6 × 10−5, 3.0 × 10−5, and 4.5 × 10−5 sec−1 at 115°, 130°, and 140°C respectively, in 2 M Na-K carbonate solution at 1 kbar pressure. At 130°C, a Cs value of 0.177 M SiO2 is reached in 30 hr, and phillipsite, clinoptilolite, and mordenite begin forming at 34, 64, and 76 hr, respectively, in 2 M CO3, 1:1 Na/K. During glass dissolution and zeolite formation, the concentration of Al as Al(OH)4− is buffered at 3.7 × 10−4 M by an unidentified phase. The ratio of SiO2 to Al(OH)4− at the onset of zeolite formation is 475. In 2 M CO3 solution, phillipsite crystallization begins at 144 hr at 115°C, at 34 hr at 130°C, and at 20 hr at 140°C. Phillipsite crystallization begins at 48 hr in 1.5 M CO3, at 168 hr in 1.0 M CO3, and in excess of 550 hr in 0.2 M CO3 at 140°C. In addition to OH− catalysis, CO32- appears also to catalyze the glass-dissolution and zeolite-formation processes.

Thermodynamically, phillipsite is unstable relative to clinoptilolite and mordenite in silica-rich alkaline hydrothermal solutions. Phillipsite forms first, followed by clinoptilolite, and then mordenite. Phillipsite formation is favored by runs of one-week duration, temperatures less than 150°C, and K-rich fluids. Clinoptilolite formation is favored in runs of more than one week, temperatures less than 150°C and K-rich fluids. Mordenite formation is favored by runs of more than one week, temperatures greater than 140°C, and Na-rich fluids. In 8-day runs at 140°C, clinoptilolite formation was favored by liquid: solid reactant (volume: mass) ratios less than 1.0, mordenite by ratios from 0.85 to 1.5, and phillipsite by ratios greater than 1.5. The mechanism of formation of the different zeolites, particularly phillipsite, may involve silica-cyclic tetramers which are abundant in concentrated solutions under alkaline hydrothermal conditions but which are almost absent in dilute low-temperature solutions. Thus, the results of hydrothermal experiments may not be directly applicable to zeolite formation at low temperatures.
Precipitation of Laumontite with Quartz, Thenardite, and Gypsum at Sespe Hot Springs, Western Transverse Ranges, California
Authors: McCulloh Thane H. , Frizzell Virgil A. , Stewart Richard J. , Barnes Ivan
Published: August 2006

Well-crystallized laumontite has been found for the first time precipitating naturally at the earth's surface at temperatures of 89° to 43°C as a component of gray to white coatings and efflorescences on exterior surface and as precipitates on interior fractures of stones and blocks lining Hot Springs Creek immediately downstream from Sespe Hot Springs, Ventura County, California. X-ray powder diffraction, scanning electron microscope (SEM), and electron microprobe analyses show thenardite to be the dominant phase in the exterior coatings, in association with minor microcrystalline (<50 μm) laumontite and gypsum. Macrocrystalline (>1 mm) laumontite is the dominant phase in interior fracture coatings and is associated with quartz, potassium feldspar, and gypsum. Trace amounts of smectite(?), halite, a mercury sulfide, an iron sulfide, an iron-bearing mineral (possibly an oxide or carbonate), and a copper mineral are also present. Zeolites other than laumontite have not been seen, and carbonate minerals are either entirely or nearly absent. SEM textures indicate nonreactive intergrowths of laumontite, quartz, potassium feldspar, and gypsum. Unbroken laumontite crystals are generally euhedral or have skeletal growth characteristics and exhibit sharp, fresh, non-corroded faces, edges, and corners.

The water issuing from the hottest and largest spring is 89°C, has a pH of 7.74, 1200 mg/liter total dissolved solids, and contains Na+, Cl−, SO42-, and H4SiO4 as the dominant dissolved species. Computations indicate that the water is supersaturated with respect to laumontite, quartz, chlorite, and prehnite and is slightly undersaturated with respect to calcite and noncrystalline silica. Water-dominated water-rock interaction is indicated by isotopic analyses. The δO18 composition expectable on the basis of the −81‰ δD composition is −11.38‰ instead of the −9.5‰ actually found (all referred to SMOW). The water chemistry suggests that the subsurface water source may have a temperature of 125°–135°C. This temperature range, together with the regionally low geothermal gradient, implies that the source is probably 3550 to 3900 m beneath the springs in fractured and permeable Mesozoic and older plutonites and gneisses.

The discovery of laumontite crystallizing at atmospheric pressure and 43°C (or lower) provides important insight into the processes responsible for burial diagenetic laumontite and a valuable perspective on the zeolite metamorphic facies.
Woolly Erionite from the Reese River Zeolite Deposit, Lander County, Nevada, and its Relationship to Other Erionites
Authors: Gude Arthur J. , Sheppard Richard A.
Published: August 2006

Woolly erionite from the Reese River deposit, Nevada, is identical in appearance to that at the type locality, near Durkee, Oregon. Both of these erionites differ in appearance from all other erionite reported in the past 20 years from diverse rocks throughout the world which are described as prismatic or acicular in habit. The non-woolly erionites are especially common as microscopic crystals in diagenetically altered vitroclastic lacustrine deposits of Cenozoic age. The Reese River woolly erionite fills joints in gray to brownish-gray lacustrine mudstone of probably Pliocene age, in a zone about 1 m thick beneath a conspicuous gray vitric tuff. Compact masses of long, curly, woolly erionite fibers are in the plane of the joint and locally are associated with opal. Indices of refraction are ω = 1.468 and ε = 1.472; hexagonal unit-cell parameters are a = 13.186(2) Å, c = 15.055(1) Å, and V = 2267.1(0.9) Å3. A chemical analysis of woolly erionite yields a unit-cell composition of: Na1.01K2.84Mg0.3Ca1.69Al8.18Si27.84O72·28.51H2O.
Cation-Exchange Reactions of Siliceous and Aluminous Phillipsites
Authors: Shibue Yasuhiro
Published: August 2006

Exchange isotherms for the pairs Na-K and Na-Ca were measured by use of 0.1 N solutions at 5°, 35°, and 70°C in phillipsite from Tecopa, California (3.63 Al/32 oxygen unit cell), and Oki Islands, Shi-mane Prefecture, Japan (6.31 Al/32 oxygen unit cell). All isotherms except those for Na-Ca at 5°C were reversible. Free energy was evaluated for all reversible exchanges. The thermodynamic affinity sequences were K > Na > Ca in both phillipsites. The selectivity for K in competition with Na and that for Na competing with Ca became larger at the lower temperatures. The siliceous phillipsite preferred the larger cation more strongly for the Na-K system, and Na more strongly for the Na-Ca system than the aluminous phillipsite.
Thermal Study of Types of Water Associated with Clinoptilolite
Authors: Knowlton Gregory D. , White Ted R. , McKague H. Lawrence
Published: August 2006

The identification and quantification of the water associated with powdered clinoptilolite and clinoptilolite-bearing tuffs were made using thermogravimetric, vacuum gravimetric, and differential scanning calorimetric techniques. Inflection points on thermogravimetric curves at approximately 80° and 170°C correspond to changes in the proportions of externally adsorbed water to loosely bound zeolitic water and loosely bound zeolitic water to tightly bound zeolitic water, respectively. These three types of water can be differentiated by temperatures and heats of dehydration obtained from differential scanning calorimetry. These temperatures and heats of hydration are 75 ± 10°C and 59.2 ± 5.9 kJ/mole H2O, 171 ± 2°C and 58.7 ± 6.1 kJ/mole H2O, and 271 ± 4°C and 78.7 ± 7.0 kJ/mole H2O for external water, loosely bound water, and tightly bound water, respectively. The ratio of loosely bound zeolitic water to tightly bound zeolitic water determined in this study is similar to that reported in the literature from structural determinations, indicating that the desorption properties of clinoptilolite are determined by the specific positions of the water molecules in the structure.
Effect of Photolytic Oxalate Treatment on Soil Hydroxy-Interlayered Vermiculites
Authors: Iyengar Sampath S. , Zelazny Lucian W. , Martens David C.
Published: August 2006

The effects of Na-citrate-dithionite (NaCD), ammonium oxalate in the dark (NH4Ox-D), and photolytic reaction under ultraviolet radiation (NH4Ox-P) on the mineralogy of <2-µm fractions of selected soils from Virginia were investigated. The NH4Ox-D treatment removed the smallest amounts of Al (<0.22%) and Fe (<0.50%) from all soils, indicating low levels of noncrystalline material in these materials. From the six soils examined, NH4Ox-P treatment extracted 5–62% more Fe and 12–300% more Al than the NaCD treatment. The NH4Ox-D and NaCD treatments revealed no X-ray diffraction detectable alterations to mineral phases present in <2-µm fractions of these soils. The NH4Ox-P treatment, on the other hand, produced considerable degradation of hydroxy-interlayered vermiculites in these soils, as evidenced by a shift of the 14-Å X-ray diffraction maxima to lower spacings with heat treatment of the sample. The NH4Ox-P treatment removed variable amounts of hydroxy-Al material from the interlayers of 2:1 layer silicates, depending on their stability and degree of development.
Hydrogen Atoms in Boehmite: A Single Crystal X-Ray Diffraction and Molecular Orbital Study
Authors: Hill Roderick J.
Published: August 2006

The crystal structure of natural boehmite, AlOOH, from Tveidalen, Langesundsfjorden, Norway, with a = 3.693(1), b = 12.221(2) and c = 2.865(1) Å, was refined from single crystal X-ray diffraction data (MoKα maximum 2θ = 120°) to an Rw value of 0.032 in space groups Amam and A21am. In both cases the proton was found to occupy positions of the type (x, 0.038, 0), where x = 0.104 and 0.396, about 0.75 Å from the donor oxygen atom. This arrangement corresponds to the presence of chains of asymmetric hydrogen bonds with random polarity parallel to the a axis, and indicates that the effective space group is Amam. No significant electron density was observed either at the center (0, 0, 0) or at the position (1/4, y, 0), corresponding to symmetric and bifurcated hydrogen bonds, respectively, between the layers of octahedra.

Calculations of the total energy of a representative portion of the boehmite structure as a function of hydroxyl orientation, using semiempirical molecular orbitals of the Hückel type, are in agreement with the observed electron density distribution and suggest a preference for (1) sp3, rather than sp2, hybridization of the donor oxygen atom orbitals, and (2) asymmetric, rather than symmetric hydrogen bonds. Disorder of the hydrogen atom positions within individual hydrogen bond chains is shown to be much less likely than disorder between adjacent fully coherent chains.
Estimation of Clay Proportions in Mixtures by X-Ray Diffraction and Computerized Chemical Mass Balance
Authors: Hodgson Mark , Dudeney A. William L.
Published: August 2006

As part of a laboratory study of the hydrothermal alteration of kimberlite, a mass balance procedure has been developed for estimating the relative proportions of synthetic phyllosilicate phases— chlorite, vermiculite, smectite, kaolinite and serpentine—present in reaction products. The procedure is based on a combination of X-ray powder diffraction (XRD) measurements (for phase identification), atomic absorption determinations (for total Si, Al, Fe, and Mg) and published analyses of clay minerals (for stoichiometric deductions). It centers on the computer inversion of a 4 × 4 matrix form of four simultaneous equations representing the mass balance of Si, Al, Fe, and Mg in four chosen minerals and incorporates a systematic routine for selecting from all possible permutations of high and low estimates of the mineral chemical analyses acceptable sets of product stoichiometries and phase proportions consistent with the total metal analyses. To minimize uncertainties and computing time, the program takes account of elemental relationships and water mass balances associated with phyllosilicates. It also accommodates data relevant to poorly crystalline phases for which a range of theoretical type-analyses modeled on aluminum oxyhydroxides and 9–11-Å, 2:1 layered aluminosilicates are employed.

The procedure produces reliable trends in phase proportions consistent with the intensities of characteristic XRD peaks of clay minerals present in the analyzed mixture; for example, increases in estimated kaolinite proportions correspond with larger 7-Å (and other) peaks in analyzed samples. A precision of 7–25% has been routinely achievable.
Interactions of Polycations of Aluminum and Iron with Clays
Authors: Oades J. M.
Published: August 2006

Polycations of limited molecular size were prepared from 0.1 M solutions of Fe(III)(NO3)3 and A1(NO3)3 by ultrafiltration. Various amounts of the polycations were added to Na-kaolinite, Na-mont-morillonite, and a Na-soil clay and the effect on the flocculation of the clay and electrophoretic mobility compared. Flocculation occurred just before zero net charge was obtained. Addition of further polycation resulted in the dispersion of clay with a net positive charge. The Al polycations possessed a high positive charge (0.49 per gram atom of Al), and their interaction with the clays indicated a planar shape. Adsorption of Al polycations decreased markedly the cation-exchange capacities of the kaolinite and the soil clay but had little effect on surface areas determined by low-temperature N2 adsorption. The Fe polycations were spheres 10–100 Å in diameter with a positive charge of 0.2 per gram atom. The surface areas of the kaolinite and the soil clay were substantially increased by the addition of the Fe polycations but their cation-exchange capacities were reduced by one fifth. Al polycations increased the surface areas of the montmorillonite (to 300 m2) presumably by propping open the interlamellar spaces and rendering the a-b planes accessible for nitrogen adsorption. The Al polycations in interlamellar spaces prevented collapse to 14 Å on heating to 150°C. There was no evidence of regular interlayer Fe as might be anticipated from the size of the spheres.
Complexes of Trimethylphosphine and Dimethylphenylphosphine with Co(II) and Ni(II) on Hectorite and on Zeolites X and Y
Authors: Schoonheydt Robert A. , Van Overloop Rudi , Van Hove Mathieu , Verlinden Johan
Published: August 2006

The gas-phase adsorption of trimethylphosphine onto hectorite, exchanged with Co(II) and Ni(II), gives trigonal complexes of the type [M(Ol)3(PMe3)]2+ (M = Co, Ni). Ten Dq values of PMe3 are 2.1 and 2.4 times larger than those of the structural oxygens or solvent molecules. The same complexes form between dimethylphenylphosphine and Ni(II) on hectorite and on synthetic zeolite Y. Co(II) forms pseudotetrahedral complexes with dimethylphenylphosphine ligands. These surface-immobilized transition-metal complexes interact strongly with NO and CH ≡ CH and to a lesser extent with CO and CH2=CH2, giving new types of complexes.
Review of Cation Ordering in Micas
Authors: Bailey S. W.
Published: August 2006

Long-range ordering of tetrahedral cations in micas is favored by phengitic compositions, by the 3T stacking sequence of layers, and by tetrahedral Si:Al ratios near 1:1. Phengites of the 1M, 2M1, and 2M2 polytypes are said to show partial ordering of tetrahedral cations, although the amounts of tetrahedral substitutions are small and the accuracies of determination are not as large as desired. The 3T structures of muscovite, paragonite, lepidolite, and protolithionite show tetrahedral ordering, as do the 2M1 brittle micas margarite and an intermediate between margarite and bityite. Muscovite-3T and margarite-2M1 are also slightly phengitic relative to their ideal compositions. Examples of octahedral cation ordering in micas are more abundant and are to be expected when cations of different size and charge are present. Octahedron M(1) with its OH,F groups in the trans orientation tends to be larger than the mean of the two cis octahedra as a result of the ordering of cations and vacancies. In some samples ordering has reduced the true symmetry to a subgroup of that of the ideal space group. If ordering in subgroup symmetry results in ordered patterns of different geometries but similar energies in very small domains, the average over all unit cells may simulate long-range disorder.
Polymerization of 2,6-Dimethylphenol on Smectite Surfaces
Authors: Sawhney B. L. , Kozloski R. K. , Isaacson P. J. , Gent M. P. N.
Published: August 2006

Air-dried samples of homoionic Na-, Ca-, Al-, and Fe-smectite were equilibrated with 2,6-dimethylphenol vapor for 24 hr. Infrared spectra of the complexes formed indicated that a portion of the sorbed phenol was transformed into quinone-type compounds. Both sorption and transformation were greatly influenced by the nature of the exchangeable cation and followed the order Fe ≫ Al > Ca > Na. Changes in the electron spin resonance spectra of the clays following interaction with the phenol followed the same order, indicating that these reactions are enhanced by a transition metal cation, such as Fe3+, on the exchange complex. The reaction products from the clay complexes were extracted with methanol and identified using ultraviolet/visible spectrophotometry, high-pressure liquid chromatography (HPLC), and mass spectrometry. The extracts contained mixtures of products including the parent phenol, di-, tri-, and tetramers of the phenol, as well as quinone and quinone dimers. The identities of these compounds were further confirmed by the coincidence of the retention times of HPLC peaks obtained from extracts of the clays with those from compounds produced by oxidation of 2,6-dimethylphenol with Ag2O.
Simplified, Complete CsCl-Hydrazine-Dimethylsulfoxide Intercalation of Kaolinite
Authors: Calvert Craig S.
Published: August 2006

The coarse (2-0.2 μm) and fine (<0.2 μm) size fractions of several soil and reference kaolinite samples were completely intercalated and expanded to 11.2 Å using a simplified CsCl-hydrazine-di-methylsulfoxide (DMSO) treatment. Rapid equilibration of the clay in hot (80°C) hydrazine monohydrate and hot (100°C) DMSO, and the use of ceramic tile mounts, limited the sample pretreatment time to only 15 min. The fine size fraction of kaolinite may be X-rayed immediately after pretreatment, though analysis of the sample 2 or 12 hr after pretreatment produced more intense, sharp basal reflections. This difference may be due to a better ordering of the DMSO-kaolinite complex with time and to a drying of the excess DMSO. The coarse size fraction of kaolinite did not entirely expand to 11.2 Å when analyzed immediately after pretreatment. A 9.6-Å peak was also present and possibly represents a mixed layering of expanded and nonexpanded kaolinite layers. The larger crystals seem to require additional time for the reaction to become complete as evidenced by the presence of an intense, sharp 11.2-Å peak and absence of the 9.6-Å peak when the coarse clay was analyzed 2 or 12 hr after sample pretreatment. Kaolinite particles <50 μm did not react completely even when they were analyzed 24 hr after pretreatment. Therefore, this technique should be limited to <2-μm particles.
Surface Potentials Derived from Co-Ion Exclusion Measurements on Homoionic Montmorillonite and Illite
Authors: Chan D. Y. C. , Pashley I. R. M. , Quirk J. P.
Published: August 2006

Simple equations are presented which allow double-layer potentials of clays to be derived from co-ion exclusion measurements in monovalent and divalent electrolyte solutions. These equations have been used to re-interpret earlier results for illite and montmorillonite. The potentials derived follow the lyotropic series for the various homoionic modification of each clay. We have demonstrated that the Schofield equation, which assumes high double-layer potentials, cannot be applied to co-ion exclusion in clay systems. Re-analysis of earlier measurements has shown that for a given homoionic clay the potentials are almost independent of concentration over the range 0.3 to 0.003 molar. Thus, clay surfaces appear to behave more like constant-potential than constant-charge surfaces.
Resilication of Bauxite at the Alabama Street Mine, Saline County, Arkansas, Illustrated by Scanning Electron Micrographs
Authors: Keller W. D. , Clarke Otis M.
Published: August 2006

Resilication of bauxite produced kaolin at and beneath an old erosion surface on bauxite at the Alabama Street Mine of ALCOA in Saline County, Arkansas. The transitional alteration can be traced in morphology by scanning electron microscopy, (SEM) and in Al:Si ratio by energy dispersive analysis. In one illustrated example, the sequence of resilication took place within 1 mm thickness; in another, across 80 mm. The first morphologic alteration of gibbsite (bauxite) appears to be to allophane that occurs in micrometer-size plates which show elongate cracking and/or straight to highly curved elongate edges. The next phase is kaolinite, first in micrometer-size flakes followed by coarser flakes that grade into a zone of typical stacked kaolinite, likewise identified by X-ray powder diffraction. Notably large stacks and small flakes of kaolinite are intimately mixed in the SEMs, thus suggesting that unequal sizes of kaolinite crystals can grow during one episode of an in-situ genesis.
Montmorillonite/Illite Stability Diagrams
Authors: Garrels Robert M.
Published: August 2006

Chemical activity diagrarns, prepared to illustrate the properties expected if mixed-layer mont-morillonite/illite is regarded as a solid solution, are compared to those derived from a treatment of these materials as a mixture of two phases. If the system is a solid solution, the coexisting aqueous solution should range from higher dissolved silica contents in the presence of kaolinite and a montmorillonite end member to lower dissolved silica in the presence of kaolinite and an illitic end member. Silica concentration in the aqueous solution might vary by a factor of as much as six. If the system is two phase, the silica content of a solution in equilibrium with kaolinite and both phases would be fixed at a given T and P, as would a solution equilibrated with both phases and K-feldspar. In the absence of a third phase, silica in equilibrium with both phases should be nearly constant, but increase with increasing ratio of K+/H+ in solution. Available data on coexisting aqueous solutions apparently are more nearly consistent with two phases than with a solid solution.
Preparation and Handling of Dithionite-Reduced Smectite Suspensions
Authors: Stucki Joseph W. , Golden D. C. , Roth Charles B.
Published: August 2006

Using Garfield, Washington, nontronite as the model mineral system, methods and apparatus were developed to prepare reduced suspensions in citrate-bicarbonate-dithionite (CBD) solution. These techniques were effective in removing excess, undesired solutes from reduced suspensions while maintaining a high Fe2+ content. They also enabled the preparation of dried, reduced films preferentially oriented with respect to the crystallographic c-axis. Supernatant solutions were collected and analyzed for Fe, Al, and Si, from which the extent of dissolution of the clay as a result of CBD treatment was assessed. Results indicated that very little Fe and Si were released to solution, but as much as about 8% of the total Al was solubilized. The highest levels of Al in solution were observed in CB treatments without dithionite.
Cation Distribution, Mössbauer Spectra, and Magnetic Properties of Ferripyrophyllite
Authors: Coey J. M. D. , Chukhrov F. V. , Zvyagin B. B.
Published: August 2006

A sample of ferripyrophyllite, a mineral with ideal composition Fe2SiO10(OH)2, was analyzed by Mössbauer spectroscopy, magnetization and magnetic susceptibility measurements. The iron is entirely ferric, and the main feature of the Mössbauer spectrum at room temperature is a single absorption line with isomer shift δ = 0.36(1) mm/sec due to iron in M2 sites. The line is broadened by a slight quadrupole splitting Δ = 0.18(1) mm/sec, the smallest yet reported for a sheet silicate. Weaker features corresponding to quadrupole doublets with relative intensities of 7% and 8% having δ = 0.43(1) mm/sec; Δ = 1.22(2) mm/sec and δ = 0.14(1) mm/sec; Δ = 0.59(2) mm/sec are assigned to ferric iron in nonequivalent octahedral and tetrahedral sites, respectively, giving the following formula, based on published chemical analysis: Ca0.05(Fe3+1.87Mg0.11Al0.09)VI(Si3.80Fe3+0.16Al0.04)IVO10(OH)2, where Ca is in interlayer sites. Ferripyrophyllite orders antiferromagnetically at 18(2)°K. The Mössbauer spectrum at 4.2°K consists of a single, resolved magnetic pattern with hyperfine field Bhf = 51.8 T. The relatively high Néel temperature compared with other dioctahedral ferric phyllosilicates provides further evidence that Fe3+ cations tend to be ordered on M2 sites within the octahedral sheet.
Reactions of Fe2+ and Fe3+ with Calcite
Authors: Loeppert R. H. , Hossner L. R.
Published: August 2006

Ferrous or ferric Perchlorate, 0.01 M, was reacted with calcite in stirred aqueous suspensions which were bubbled vigorously with an oxidizing purge gas. Two and three equivalents of CaCO3 were dissolved per mole of Fe2+ and Fe3+ neutralized, respectively. With Fe(ClO4)2, the crystalline Fe oxide products partially coated the calcite surface. The dominant products were lepidocrocite and goethite when the purge gas was air or 20% CO2 (balance air), respectively. After reaction with Fe2+ the edges and corners of the calcite crystals were generally rounded and the faces were non-uniformly pitted; however, after reaction with Fe3+, a mosaic pattern with distinct ridges and channels was evident on the calcite. These ridges were somewhat pitted, but distinct stepped dislocations were present leading to a featureless and generally flat channel floor. When the calcite was separated from the Fe solution by a semi-permeable membrane, precipitation occurred predominantly on the calcite side and on the Fe side of the membrane in the Fe2+ and Fe3+ systems, respectively.

Fe oxyhydroxides precipitated from the Fe(ClO4)3 and Fe(ClO4)2 solutions by different mechanisms. In the Fe(ClO4)3 system, although the initial reaction may have been at the calcite surface, the bulk of the poorly crystalline ferrihydrite was formed by hydrolysis of Fe polymers in suspension. Neutralization occurred by the reaction with basic products of a surface-controlled dissolution of calcite, rather than by a direct reaction of acidic polymers with the calcite surface. In the Fe(ClO4)2 system, lepidocrocite or goethite formed by the partial hydrolysis of Fe2+ or Fe3+ by reaction with calcite or the basic products of calcite dissolution and subsequent precipitation of simple Fe species on existing FeOOH nuclei.
Comparison of Intercalation Methods for Differentiating Halloysite from Kaolinite
Authors: Theng B. K. G. , Churchman G. J. , Whitton J. S. , Claridge G. G. C.
Published: August 2006

The intercalation of formamide, potassium acetate, and hydrazine by halloysite and/or ka-olinite-rich samples, with and without subsequent displacement of the interlayer species by water or glycerol/water, has been investigated. Halloysite, as such, or in mixtures with kaolinite is completely expanded by all the treatments used, thereby enabling halloysite concentrations to be determined from the basal X-ray powder diffraction (XRD) peak ratios of the appropriate complexes. The values so obtained are usually proportional to the abundance of tubes, laths, and spherules in the transmission electron micrographs of the samples. The analysis of kaolin samples (halloysite plus kaolinite) by intercalation methods is less straight forward because a proportion of the kaolinite component in the system may not expand, even after lengthy (≥ 18 days) contact of the sample with the intercalating agent. Only prolonged immersion in hydrazine produces complete or nearly complete expansion of this component. When allowance is made for the presence of non-clay mineral components, kaolin-mineral percentages estimated from XRD peak intensity ratios of the hydrazine complexes generally agree with values derived from differential thermal analysis to within ±10%. Kaolinite in mixtures with halloysite cannot be directly determined by intercalation procedures inasmuch as treatments which result in complex formation with kaolinite also expand halloysite. In such systems, kaolinite can be estimated by difference between the concentration of kaolin minerals and halloysite.
Hisingerite Material from a Basalt Quarry Near Geelong, Victoria, Australia
Authors: Shayan Ahmad
Published: August 2006

A material resembling what has been described in the literature as hisingerite has been identified in the joints of Cenozoic grey basalt near Geelong, Victoria. The material gives an X-ray powder diffraction pattern with weak broad peaks at 4.49, 2.58, and 1.53 Å and a chemical analysis of SiO2 = 34.2, TiO2 = 0.28, A12O3 = 4.16, Fe2O3 = 17.10, FeO = 3.52, MnO = 0.04, MgO = 5.19, CaO = 0.68, Na2O = 0.26, P2O5 = 0.05, H2O+ = 5.3, H2O− = 25.4, total = 96.18% (3.82% siderite impurity). Assuming a smectite model with 44 negative charges per unit cell, the chemical composition gives a unit-cell formula with −1.14 charges, corresponding to a cation-exchange capacity (CEC) of 135 meq/100 g. The same unit-cell charge is obtained when the structural formula is calculated on the basis of (Si + Al) = 8. The measured CEC of 60 meq/100 g indicates that the smectite structure may not apply to this hisingerite-material, and that in the alternative structure, all of the Al atoms may not be in the tetrahedral positions. Although the specific surface area of this material is between 662 and 758 m2/g (comparable to that of smectite), the infrared spectra do not show the characteristic OH vibrations, and the thermal analysis curves lack the dehydroxylation peak at 550–600°C expected for a smectite. Transmission electron microscopy shows indications of a layer structure and apparently hollow spherical bodies with ‘onion’ structure of 140 to 200 Å internal diameter, which might represent the sites of the large amounts of water contained by the material. The mode of occurrence and the nature of the hisingerite-material suggest precipitation from solution at relatively low temperatures.
Smectite Interactions with Flavomononucleotide
Authors: Mortland M. M. , Lawless J. G. , Hartman H. , Frankel R.
Published: August 2006

Adsorption isotherms and UV-visible and Mössbauer spectroscopic data point to specific interactions between flavomononucleotide (FMN) and Fe3+-smectite. The maximum amount of FMN adsorption was 0.3 mmole/g of Fe3+-smectite giving a 1:1 molar proportion of Fe3+ and FMN. The results suggest a Fe3+-FMN complex residing at the smectite surface. Other homoionic smectites (Cu2+, Zn2+, and Ca2+) exhibited lower levels of adsorption and less apparent specific interaction.
Effect of Selective Dissolution on Charge and Surface Properties of an Acid Soil Clay
Authors: Cavallaro Nancy , McBride M. B.
Published: August 2006

To evaluate the importance of oxides to the surface chemistry of acid mineral soils, clay fractions were separated from a surface and subsurface horizon of an Inceptisol representative of many of the acid soils of the Southern Tier of New York state. Portions of the clays were treated to remove selectively noncrystalline and microcrystalline Fe and A1 oxides (acid ammonium oxalate extraction), total free iron oxides (dithionite reduction in buffered citrate solution), and organic matter (hypochlorite oxidation). Charge and ion-adsorption characteristics of the treated and untreated clays were investigated by means of Ca2+- and Cl−-exchange capacities, potentiometric titrations, and electrophoretic mobility (zeta potential) measurements of the CaCl2-treated clays.

Based upon surface area and anion- and cation-exchange measurements, the Fe and A1 oxides or oxideorganic matter complexes were found to contribute a large part of the surface area and pH-dependent charge of these clays. Oxide removal increased the cation-exchange capacity (CEC) and virtually eliminated the anion-exchange capacity (AEC) at pH 3 and 5.5 while shifting the positive zeta potential (ZPC) of the B-horizon clay toward negative values. Organic matter oxidation increased the AEC at pH 3 and the CEC at pH 5.5 and markedly shifted the ZPCs of both A- and B-horizon clays toward more positive values, probably by the removal of adsorbed organics from oxide surfaces. Estimates of the ZPCs of the clays varied among the three methods used, Ca2+- and Cl−-exchange capacities giving the lowest, and electrophoresis giving the highest values.
Reaction of Benzene with Cu(II)- and Fe(III)-Exchanged Hectorites
Authors: Eastman M. P. , Patterson D. E. , Pannell K. H.
Published: August 2006

The reaction of benzene with exchangeable Cu(II) and Fe(III) in hectorite clay films was studied by electron paramagnetic resonance (EPR). The reaction when carried out in a sealed tube between 60° and 100°C produced a variety of organic radical products. The nature of these products depended on the concentration of water in the reaction medium and the reaction time. The free radicals were accompanied by a reduction in the oxidation state of the metal ions; this process had a zero-order dependence on the metal ion concentration. The activation energies determined from the zero-order rate constants are 67 ± 11 kJ/mole (Cu(II)) and 46 ± 6 kJ/mole (Fe(III)). The free radicals initially formed under anhydrous conditions appeared to populate sites in the interlayer region; the activation energies determined for this first order process are 57 ± 9 kJ/mole (Cu(II)) and 42 ± 3 kJ/mole (Fe(III)). These activation energies are within experimental error of those determined from the metal ion kinetics. The EPR signal due to organic radicals showed little temperature dependence; thus, exchange processes involving organic free radicals were probably not important in determining EPR lineshapes.
Effects of Oxidation State of Octahedral Iron on Clay Swelling
Authors: Stucki Joseph W. , Low Philip F. , Roth Charles B. , Golden D. C.
Published: August 2006

Three montmorillonites and a nontronite were reduced by sodium dithionite to obtain different amounts of Fe2+ in their octahedral sites. The mass ratio of water to clay, mw/mc was determined as a function of Fe2+ at several values of the swelling pressure, π. The value mwmc decreased markedly with increasing Fe2+ at each value of π for each clay. Moreover, curves of π vs. mwmc for the different clays were displaced downwards as Fe2+ increased. A straight line was obtained when In(π + 1) was plotted against 1/(mw/mc) however, at some oxidation states of three of the samples this line exhibited a sharp break at a specific value of 1/(w/mc. The slope of the line decreased for each clay as Fe2+ increased, and an increase in Fe2+ was accompanied by an increase in the cation exchange capacity. These observations are thought to be due to a collapse or partial collapse of the superimposed clay layers resulting from the increase in cation-exchange capacity.
Effect of pH on the Rheology of Marine Clay from the Site of the South Nation River, Canada, Landslide of 1971
Authors: Torrance J. Kenneth , Pirnat Maria
Published: August 2006

The pH of Na-saturated, carbonate-containing and carbonate-free Leda clay, at salinities of 2 and 10 g/liter, was decreased from pH 8 to 4 by the addition of HCl. The Bingham yield stress, as determined with a coaxial viscometer, increased in all materials as the pH decreased. Above about pH 7 the 2-g/liter materials had a lower yield stress at any water content than the 10-g/liter materials, whereas, below about pH 6.8 the yield stress of the carbonate-containing soil at a salinity of 10 g/liter was lower. For the carbonate-free material, the change occurred at about pH 6.2. The influence of salinity on the remolded shear strength of these materials was pH-dependent. A yield stress increase with decreasing pH was likely due to a change in ion saturation. The carbonate-free material exhibited a maximum yield stress at about pH 5.5–6.2, depending on salinity. The isoelectric points for oxides and clay mineral edges most probably account for the existence of the maximum.
Crystal Chemistry of Corrensite: A Review
Authors: Brigatti Maria Franca , Poppi Luciano
Published: August 2006

Statistical analyses of chemical data from the literature of corrensite minerals suggest a large compositional variability, more evident in octahedral than in tetrahedral coordination. Mg occupies 40–80% of the octahedral sites, with Al and Fe2+ making up the remainder. Approximately 15–30% of the tetrahedral sites are filled by Al. Despite this compositional variability, distinct fields for the several types of mixed-layer trioctahedral chlorite/trioctahedral swelling layer are not apparent. Statistical analyses of the composition of corrensite compared with saponite, vermiculite, and chlorite suggest that corrensite is an intermediate between trioctahedral chlorite and trioctahedral smectite. If Fe/(Fe + Mg) > 50%, chlorite alone is favored, but with increasing Mg, chlorite appears to transform into corrensite and then, by iron oxidation, into trioctahedral smectite. Despite the chemical variability between corrensite, chlorite, and saponite, corrensite appears chemically to be a well-defined species. On the other hand, corrensite cannot be characterized chemically on the basis of its swelling component. Thus, the current definition of corrensite as a regular 1:1 interstratification of trioctahedral chlorite and either trioctahedral smectite or vermiculite is appropriate.
Colloid Stability of Clays Using Photon Correlation Spectroscopy
Authors: Novich B. E. , Ring T. A.
Published: August 2006

Photon correlation spectroscopy (PCS), a dynamic light-scattering technique for particle size measurement, was used to determine the coagulation rates of aqueous dispersions of relatively monodisperse South Carolina Peerless kaolinite, Silver Hill, Montana, illite, Wyoming montmorillonite, and Florida palygorskite. This technique allows quantitative measurement of the rate of coagulation for clay particles where the traditional turbidity method gives only a qualitative measure. The critical coagulation concentrations for KCl at pH = 10.0 were: 0.199 M for kaolinite, 0.202 M for illite, 0.290 M for montmorillonite, and 0.034 M for palygorskite. The effective Hamaker constants, calculated using Derjaguin-Landau-Verwey-Overbeek theory, were: 3.1 × 10−20 J for kaolinite, 2.5 × 10−20 J for illite, 2.2 × 10−20 J for montmorillonite, and 1.63 × 10−19 J for palygorskite. Stern potentials at the critical coagulation concentration at pH 10.0 were: −42.7 mV for kaolinite, −40.7 mV for illite,‒21.2 mV for montmorillonite, and −66.9 mV for palygorskite.
Chemisorption of Copper on Hydroxy-Aluminum-Hectorite: An Electron Spin Resonance Study
Authors: Harsh J. B. , Doner H. E. , McBride M. B.
Published: August 2006

Copper adsorption on a hydroxy-aluminum-hectorite complex (OH-Al-hectorite) at pH 4.5, 5.7, 7.4, and 7.8 was examined by means of electron spin resonance. The spectra of these samples were compared to those of Cu2+-hectorite and various aluminum hydrous oxides. Copper on the OH-Al-hectorite in aqueous gels occurred as mobile Cu(H20)62+ and chemisorbed to discrete sites of the OH-Al interlayer. As pH was increased, the ratio of chemisorbed to mobile Cu2+ increased. At pHs above 7 the solubility product of Cu(OH)2 was exceeded, but chemisorbed Cu2+ remained as the dominant species. These results contrast with the precipitation of Cu observed on microcry stalline gibbsite above pH 5 and indicate that the interlayer OH-A1 retained more Cu2+ on discrete sites. The greater adsorption capacity probably resulted in part from a higher specific surface area. Electron spin resonance spectra of Cu2+ in air-dried films of the OH-Al-hectorite at pH 4.5 and 7.4 showed Cu2+ in square planar symmetry, oriented with the z-axis perpendicular to the OH-Al-hectorite a-b plane. At the higher pH, the spectrum resembled that of Cu(OH)42- on alumina, suggesting a ligand exchange mechanism for Cu2+ adsorption on the complex.
Mechanism of Sulfate Adsorption by Kaolinite
Authors: Rao Sudhakar M. , Sridharan A.
Published: August 2006

Sulfate adsorption on kaolinite was followed at 0.7 μeq/ml to 99 μeq/ml solution concentrations at 30°C and at pH 6.0, and the amount of OH~ ions released and the change in surface charge were determined. Sulfate was adsorbed at positive and neutral sites by displacing OH2 and OH− groups, respectively. Adsorption of sulfate occurred predominantly at positive sites at low (0.7 μeq/ml to 0.9 /μeq/ml) solution concentrations, whereas at higher solution concentrations, the proportion of the sulfate adsorbed at the neutral sites increased, varying from 51% at 4.9 μeq/ml to 68% at 99 μeq/ml. The form of sulfate bonding was apparently governed by the level of the positive charge on the clay surface. Higher positive charge at low and intermediate levels of sulfate saturation resulted in the adsorption of sulfate as a divalent anion by forming a 6-member ring with surface Al. With a decrease in positive charge at higher levels of adsorption, the sulfate ion formed both monodentate and bidentate complexes.
Polytypism of Micas. I. MDO Polytypes and Their Derivation
Authors: Backhaus K.-O. , Ďurovič S.
Published: August 2006

A procedure leading to the systematic derivation of all maximum-degree-of-order (MDO) polytypes in the three mica families, based on the order-disorder (OD) interpretation of mica structures, has been developed. There are 6 non-equivalent (8 non-congruent) homo-octahedral, 14 (22) mesooctahedral, and 36 (60) hetero-octahedral MDO mica polytypes. The ideal ditrigonalization of tetrahedral sheets leads to a splitting of the polytypes in any mica family into two subfamilies with octahedral and trigonal prismatic coordination of the interlayer cations, respectively.
Domain Segregation in Ni-Fe-Mg-Smectites
Authors: Decarreau A. , Colin F. , Herbillon A. , Manceau A. , Nahon D. , Paquet H. , Trauth-Badaud D. , Trescases J. J.
Published: August 2006

The first stage of lateritic weathering of pyroxenes in the Niquelandia area, Brazil, leads either to Fe-rich products or to a phyllosilicate clay. In relatively unfractured parent rock the phyllosilicate clay contains Ni-rich smectites, the atomic ratio of Ni: octahedral cations ranging from 0.3 to 0.5. These smectites were studied by polarized light microscopy, X-ray powder diffraction (XRD), transmission electron microscopy, and electron microprobe, and infrared, optical absorption, Mössbauer, and extended X-ray absorption fine-structure (EXAFS) spectroscopy. The chemical composition of the smectite is constant on the optical microscope scale even to the smallest analyzed particles (3000 A in diameter and about 75 Å thick). From XRD data the mineral is principally a swelling, trioctahedral smectite; however, some kerolite-pimelite-like layers are present, and a weak 06,33 reflection indicates the presence of a small amount of a dioctahedral phase. Mössbauer results show that all Fe cations are Fe3+ in octahedral sites. The structural formula of the smectite is: (Ca0.01K0.05)(Al0.17Fe0.5Mg0.48Ni1.47Cr0.02)(Si3.92Al0.08)O10(OH)2

The results obtained from all the above methods suggest that in the smectites Ni, and, perhaps, a small amount of Mg are clustered in pimelite-like domains (or layers), whereas Fe and some Al are clustered in nontronite-like domains (or layers). Most selected-area electron diffraction patterns exhibit continuous or punctuated (hk) rings, indicating that particles contain several stacked layers. The patterns of some thin particles, however, suggest dioctahedral layers having trans-octahedral vacancies, such as in the Garfield, Washington, nontronite. Thus, the Ni-Fe-Mg-smectite, which seemingly is homogeneous, actually consists of mixed trioctahedral and dioctahedral layers or domains.
Effect of Silicate Species on the Transformation of Ferrihydrite into Goethite and Hematite in Alkaline Media
Authors: Cornell R. M. , Giovanoli R. , Schindler P. W.
Published: August 2006

The transformation of ferrihydrite to goethite and/or hematite in alkaline media is strongly retarded by the presence of silicate species. These species probably stabilize ferrihydrite by adsorbing on the particles of ferrihydrite and linking them into an immobile network.

At concentrations low enough for the transformation to proceed, silicate species promote the formation of hematite and hinder the nucleation of goethite. The presence of silicate species modifies the morphology of both reaction products. Hematite forms ellipsoidal single crystals, commonly displaying outgrowths of goethite. Silicate species in solution appear to enhance the development of the (021) faces of goethite, probably by preferential adsorption on these faces; at high levels of silicate species, goethite crystals adopt a pseudohexagonal habit. This morphology has not been observed previously for goethite.