bluuebunny/crossref_metadata_2025 huggingface dataset:
Effect of Particle Size on Potassium Sorption by Potassium-Depleted Phlogopite
Authors: Ross G. J. , Rich C. I.
Published: September 2006

Sorption of K from mixed KCl and CaCl2 solutions by K-depleted, Ca-saturated phlogopite was studied to determine the effect of particle size. The experiments were done at room temperature with 25 mg of K-depleted phlogopite samples in 50 ml solutions which were 0·002 N with respect to KCl and 0·02 N with respect to CaCl2.

Sorption of K increased sharply with increase in particle size. The 54–75 μm fraction sorbed nearly all, whereas the 0·2–2 μm fraction sorbed less than half, of its depleted K. The 5–20 μm fraction sorbed an intermediate amount. This relationship is explained by the same hypothesis which accounts for the increase of K release with increase in particle size. That is, bending of unit mica layers due to peripheral expansion is greater in large and thick particles than in small and thin ones. This increased bending induces the greater K release from large particles. Similarly, bending due to peripheral collapse of hydrated layers is greater in large particles than in small ones. Thus, more energy is needed to initiate layer collapse and restrict further K uptake in the large particles which results in their greater K sorption capacity.

These results imply that in natural conditions, as in soils, the coarse vermiculite and weathered mica fractions may be more effective in sorbing K from solution than their fine counterparts.
Exchangeable Cation Distribution in Nickel- and Magnesium-Vermiculites
Authors: Alcover J. F. , Gatineau L. , Mering J.
Published: September 2006

Abnormal scatterings of X-rays take place between Bragg spots. Their study in hydrated Mg- and Ni-vermiculites shows that they appear in reciprocal space in the form of modulated lines, elongated along the Z* axis. These scatterings demonstrate a two-dimensional organization of the compensating cations and of the water molecules in the interlamellar layer. In such ordered domains, the cations are situated at the nodes of a biperiodic centered lattice with parameters 3a,b.

The distribution of compensating cations must conform with the charge distribution which they neutralize; it can therefore be concluded that the distribution of effective negative charges (tetrahedral negative charges less positive octahedral charges) is also at least partially ordered.
Mössbauer Studies of Small Particles of Iron Oxides in Soil
Authors: Gangas N. H. , Simopoulos A. , Kostikas A. , Yassoglou N. J. , Filippakis S.
Published: September 2006

A soil of Attica (Greece) has been studied by Mössbauer spectroscopy and magnetization measurements in order to ascertain the nature and form of iron oxides present in it. The room temperature spectra consist of a paramagnetic doublet and a small magnetic sextet. At liquid nitrogen temperature the magnetic component increases considerably at the cost of the paramagnetic component. This behavior is typical of superparamagnetism exhibited by ultrafine magnetic particles. From the values of hyperfine parameters extracted by computer fits of the spectra, the particles can be identified mainly as α-Fe2O3. The theory of superparamagnetism, in conjunction with Mössbauer and magnetization data, is discussed in detail. Application of this theory to the data for the clay fraction of the soil leads to the conclusion that the oxide particles have a size distribution with a mean particle diameter of 131 Å and a width of 14 Å.
An Expansible Mineral Having High Rehydration Ability
Authors: Tomita Katsutoshi , Dozono Mitsuhiko
Published: September 2006

An interstratified mineral (mica-montmorillonite) from a hydrothermally altered andesite in the southern part of Satsuma Peninsula, Japan fully rehydrates after having been heated to 800°C.
Determination of the Cation Exchange Capacity of Clays and Soils Using an Ammonia Electrode
Authors: Busenberg E. , Clemency C. V.
Published: September 2006

The ammonia electrode serves as the basis of a simple, accurate method for determination of cation exchange capacity of small (ca. 50 mg) samples of clays. The technique is also capable of accurate measurement of CEC values on the order of 0·01 m-equiv/100 g if larger (ca. 500 mg) samples are used. The procedure, which requires saturation of the exchange sites with ammonium as in the usual methods, utilizes the electrode in the determination of ammonia released by treatment of the ammonium clay by strong base. For a Wyoming bentonite, the technique gave a CEC of 86 m-equiv/100 g with an S.D. (four determinations) of 0·83 m-equiv/100 g. Duplicate runs on the same sample by the conventional Kjeldahl method gave results of 86·0 and 85·5 m-equiv/100 g.
Electrochemical Modifications in Kaolinite-Glass Bead Plugs
Authors: Sethi A. J. , Herbillon A. J. , Fripiat J. J.
Published: September 2006

Electrochemical treatment of kaolinite-glass bead plugs in the presence of water and CaCl2 solutions produces dissolution of the glass beads, corrosion of the anodes, and transport of the released elements toward the cathodic zone. In this area, new mineral phases (both amorphous and crystalline) are synthesized. Most of these new phases, and especially the calcium silicate hydrate (CSH-1), are well known to exhibit important cementing properties. The nature and the extent of the modifications brought about by the treatment are dependent on the nature of the electrodes, the pH and the ionic strength of the circulating electrolyte, and the duration of the treatment.
Iron-Rich Saponite (Ferrous and Ferric Forms)
Authors: Kohyama Norihiko , Shimoda Susumu , Sudo Toshio
Published: September 2006

Clayey fragments colored deep bluish-green are widely found in glassy rhyolitic tuffs at Oya, Tochigi Prefecture. In room-air the color changes to black or gray within one hour and finally to brown in a few weeks. The fragments are composed of an intimate mixture of two kinds of smectite: a ferrous iron-rich smectite (IR) with b0 = 9·300 Å; and an iron-poor smectite(IP) with b0 = 9·030 Å. Microscopic examination shows a vesicular texture and that IR occurs at the core and IP at the marginal parts of each vesicle. Analysis by EPMA gave the following structural formulas: IR, (Na0·60K0·04Ca0·44) (Mg2·04Fe3·982+Al0·02) (Si6·36Al1·64)O20(OH)4; IP, (Na0·52K0·08Ca0·26) (Mg0·90Fe0·952+Al2·54) (Si7·66Al0·34)O20(OH)4. IR has a much larger amount of iron in trioctahedral sites than that found in any earlier data. Acid-dissolution data, infrared absorption spectra, Eh-values, and DTA and TG curves are also given. Ferrous iron in the structure is easily oxidized in room air with loss of protons from the clay hydroxyls and with contraction of the lattice. We call the IR before and after oxidation the ferrous and ferric forms, respectively, of iron-rich saponite. They strongly suggest the existence of the iron-analogue of saponite. On exposed weathered surfaces in the field, brown fragments tend to be differentiated into two parts: one light yellow montmorillonite-beidellite; the other a brown incrustation due to hisingerite.
Phase Transitions in Complexes of Nontronite with n-Alkanols
Authors: Pfirrmann G. , Lagaly G. , Weiss Armin
Published: September 2006

The basal spacings of long chain n-alkanol complexes of nontronite saturated with Li+, K+ Mg2+, Ca2+, Sr2+ and Ba2+ were measured for temperatures increasing from −70°C up to 130°C. With rising temperatures the complexes rearrange from a low temperature form into a high temperature form.

In the low temperature form the alkyl chains of the alkanol molecules form bilayers with their chain axes perpendicular to the silicate layers. The chains may not be in all cases in the planar all trans conformation but in special ‘kink’-conformations.

The transition into the high temperature form is explained by cooperative transition from a form with a low number of ‘jogs’ to one with a high number of ‘jogs’ and ‘kinks’.
Adsorption and Oxidation of Benzidine and Aniline by Montmorillonite and Hectorite
Authors: Furukawa T. , Brindley G. W.
Published: September 2006

Quantitative measurements are made of the adsorption of benzidine and aniline from aqueous hydrochloride solutions by Na-, Li-, and Ca-montmorillonite and of the displaced inorganic cations. From these data, the ionic states of the adsorbed organic species are determined. Under conditions of controlled pH, the adsorption of benzidine increases as the pH increases, and involves mainly divalent species at pH<3·2, and increasing proportions of monovalent and neutral species at pH> 3·2. With aniline, monovalent and neutral species are adsorbed, and hydrogen ions also appear to participate in the reactions.

Color developments of benzidine and aniline complexes of montmorillonite and hectorite are considered qualitatively in relation to the adsorption data, to various experimental conditions including the nature of the inorganic exchangeable cations, the pH, and the presence or absence of oxygen in the system, and to relevant previous work. It is hypothesized that the blue color of the benzidine complex is due to semiquinone formation by oxidation on montmorillonite by the clay itself, and on hectorite by dissolved oxygen or H2O2, and that the yellow color under acid conditions arises from reversible formation of quinoidal cations from semiquinones. The color developments of the aniline complex are due probably to oxidation of aniline by atmospheric oxygen.
Segregation and Exchange Properties of Alkylammonium Ions in a Smectite and Vermiculite
Authors: McBride M. B. , Mortland M. M.
Published: September 2006

X-ray diffraction analysis of mixed alkylammonium-exchanged smectite revealed segregation of different ion species into randomly ordered layers. Vermiculite, however, showed segregation into crystallites, a behavior attributed to clay inhomogeneity. Ion segregation is explained by the hydration properties of cations as well as the energy requirements of layer expansion. Quaternary ammonium ions of different size were used to exchange ethylammonium-clays, and the effectiveness, as well as steric hindrance, of cation size in ion exchange was demonstrated. Layer charge density was related to the degree of ease of large cation adsorption. Basal spacing in suspension was found to be important in determining the preference of vermiculite for certain cations, while more freely-expanding, lower layer charge smectite did not demonstrate this phenomenon.
New Stability Diagrams of Some Phyllosilicates in the SiO2-Al2O3-K2O-H2O System
Authors: Huang W. H. , Keller W. D.
Published: September 2006

Aluminum is treated as a mobile, reactive component in newly designed stability diagrams for the SiO2-Al2O3-K2O-H2O system. The diagrams show that the stability field of kaolinite is strongly dependent on pH at or below 6·7 but at 6·7 or greater the stability field is independent of pH, and also that in present sea water, K-mica is a stable phase with respect to kaolin minerals. Natural waters from present-day, kaolin-forming localities in Mexico and Kentucky are consistent with theoretical interpretations from these stability diagrams.
Oxidative Power of Smectites Measured by Hydroquinone
Authors: Thompson Thomas D. , Moll William F.
Published: September 2006

The oxidative power of a smectite can be measured quantitatively by oxidation of hydro-quinone to p-benzoquinone in a clay slurry. Oxidation takes place in the presence of O2 (air) but not N2 unless Fe3+ or Cu2+ are the exchangeable cations. This study examined 26 smectite samples with varying compositions and processing. The oxidative power increases with decreasing Li-fixation and increasing cation exchange capacity. Li-fixation does not depend upon the tetrahedral Al. The cation exchange capacity can decrease markedly by mere storage in water.

The oxidation proceeds principally on the surface by adsorbed oxygen molecules or radicals. A mechanism is proposed. With Fe3+ or Cu2+ present, even under N2, oxidation occurs via electron transfer. With smectites containing Fe2+, both the Fe and the hydroquinone are oxidized in the same reaction.
Discussion of the Occurrence and Origin of Sedimentary Palygorskite-Sepiolite Deposits
Authors: Isphording Wayne C.
Published: September 2006

Marine and non-marine palygorskite-sepiolite deposits are found throughout the world and occur interbedded with chert, dolomite, limestone, phosphates and other non-detrital sedimentary rocks. The origin of these high-magnesium clays has long been attributed to either alteration of volcanic ash or the structural transformation of smectite clays. More recently, others have argued origin by direct crystallization (neo-formation). Recent laboratory studies support this latter concept, particularly in environments where the concentration of alumina is low, the silica concentration high, and the pH alkaline. Such an origin is proposed for the Georgia-Florida deposits in southeastern United States, since major obstacles exist against formation by alteration of volcanic ash or by transformation of smectites. Lateritic weathering during the Miocene would have favored direct precipitation of these clays in the shallow, marginal seas. The basinward increase in the MgO: Al2O3 ratio is further support.

Deep weathering of crystalline rocks in northern British Honduras and Guatemala would have produced similar high silica, low alumina conditions on the adjacent submerged Yucatan Platform during the late Tertiary. The seaward increase in the MgO: A12O3 ratio, the lack of associated detrital constituents, and the absence of associated smectites strongly indicate a similar origin by direct crystallization of these Yucatan palygorskite-sepiolite clays.

Some occurrences of palygorskite and sepiolite may well be related to the alteration of smectite clays or volcanic ash. However, many of the large sedimentary deposits are more probably the result of direct crystallization adjacent to areas undergoing tropical or subtropical weathering.
Bentonite Characteristics from Deposits near Rosalind, Alberta
Authors: Scafe D. W.
Published: September 2006

Two bentonite deposits having average thicknesses of 10 and 4 ft are exposed within nonmarine strata of Late Cretaceous age along the Battle River near Rosalind, Alberta. They are characterized by scarcity of >44μm material and variable 44-2μm and <2μm contents. Material >44μm in size in excess of 2 per cent is primarily attributable to secondary calcite, and <2μm content may be related to the amount of 44-2μm material that has altered diagenetically from volcanic glass to montmorillonite. Rhyodacite was the probable composition of the parent ash; therefore, the high iron content in one deposit is probably due to diagenesis. The blocking effect of iron on exchange sites can explain differences in exchangeable Na and Ca in different deposits. High exchangeable Na found in finer subdivisions of fractionated clay can be explained by increased purity of the bentonite.

Multiple regression analysis of the analytical data shows that 48 per cent of the variation in yield (bbl/T.) of 15 centipoise drilling mud can be attributed to concomitant variation in seven interrelated compositional properties. Sequential analysis shows that <0·2μm clay content is the most important contributor to variation in yield. The remaining variables (total clay content, exchangeable Na, exchangeable Ca + Mg, Fe2+and Fe3+contents, and CEC) contribute little additional precision to the regression analysis when <0·2μm clay content is included in the equation.
Clay Mineralogy of Some Silty Soils of the Inner Coastal Plains of Mississippi
Authors: Nash V. E. , Glenn R. C.
Published: September 2006

The chemical and mineralogical properties of six soils previously believed to be developed from coastal plain sediments were found to be significantly influenced by thin loess overlays and admixtures. The study included two profiles each of the Atwood, Lucedale and Savannah series. Atwood formed primarily in deep loess over coastal plain sediments, Lucedale showed definite loess influence to a depth of 10 in. and possible mixing to a greater depth, whereas the Savannah indicated the presence of slight loess to a depth of 20 in. Both the Atwood and Lucedale soils are well drained, whereas Savannah is moderately well drained and contains a fragipan.

The mineralogy of the coarse clay (2-0·2 μm) appeared to be the most diagnostic feature indicating genetic differences among the soils. Montmorillonite in this clay fraction was most abundant in Atwood, diminished in Lucedale and occurred only in trace amounts in Savannah. In both the Atwood and Lucedale soils very little montmorillonite was found at depths of 35 in. where coastal plain influence apparently predominates. Conversely, aluminous vermiculite-chlorite intergrade minerals were least abundant, in Atwood, increased in Lucedale and occurred in greatest amounts in Savannah.

Accompanying these changes in mineralogy were corresponding changes in the chemical properties. Although no consistent differences in Ca and Mg content were found between the Atwood and Lucedale soils, both Atwood and Lucedale were much higher in exchangeable Ca and Mg than Savannah. Soil pH and base saturation increased in the order Savannah, Lucedale and Atwood.
An Ultraviolet Spectroscopic Method for Monitoring Surface Acidity of Clay Minerals under Varying Water Content
Authors: Bailey George W. , Karickhoff S. W.
Published: September 2006

The ability of a clay mineral surface to function as an acid is not represented by bulk pH measurements. A method using u.v. analysis and organic indicators has been developed to monitor surface acidity. The u.v. organic indicator method enables sensitive in situ quantification of surface-induced protonation in wet or dry clay systems. The clay preparation procedure used yields reproducible acidic behavior.
Mica-Derived Vermiculites as Unstable Intermediates
Authors: Kittrick J. A.
Published: September 2006

Stability determinations were made by solubility methods on two trioctahedral mica-derived vermiculites. The phlogopite-derived vermiculite was found to be unstable under acid solution conditions, where stabilities of montmorillonite, kaolinite and gibbsite had previously been determined. An attempt was next made to locate a possible montmorillonite-vermiculite-amorphous silica triple point. This triple point involved conditions of alkaline pH, high pH4SiO4 and high Mg2+. These are conditions where phlogopite and biotite-derived vermiculites are most likely to control equilibria if they are stable minerals. The montmorillonite-vermiculite-amorphous silica samples went to the montmorillonite-magnesite-amorphous silica triple point, leaving no stability area whatsoever for the vermiculites. These large particle-size, trioctahedral, mica-derived vermiculites appear to be unstable under all conditions of room T and P.

Arguments are presented indicating that micas are unstable in almost all weathering environments. A hypothesis is proposed that mica-derived vermiculites result from the unique way in which unstable micas degrade in these environments. It is proposed that vermiculite derives from a series of reactions whose relative rates often result in an abundance of vermiculite. These relative reaction rates are slow for mica dissolution, rapid for K removal and other reactions pursuant to vermiculite formation, and slow for vermiculite dissolution. In chemical terms, mica-derived vermiculites may be considered fast-forming unstable intermediates.
Properties of Reduced Charge Montmorillonites: Hydrated Cu(II) Ions as a Spectroscopic Probe
Authors: Clementz David M. , Mortland M. M. , Pinnavaia Thomas J.
Published: September 2006

A series of Cu(II) reduced charge montmorillonites (RCM) of varying charge reduction has been prepared by exchange of the parent Li(I)-Na(I) mineral with CuCl2 in 95 per cent ethanol solution. The Cu(II) exchange capacity, as determined by Na(I) exchange in 1:1 (v/v) ethanol-water, is a linear function of the fraction of Li(I) initially present on the exchange sites, F. Selective Cu(II)-saturation on internal and external sites was achieved at maximum charge reduction (F = 1.0). Water sorption isotherms and (001) basal spacings are interpreted in terms of an increasing tendency toward interlayer collapse with increasing charge reduction. Because of the higher hydration energy of the Cu(II) ion, however, the fraction of non-expansible interlayers at a given F value is lower than those present in the corresponding Li(I)-Na(I) RCM. Electron spin resonance spectra of oriented samples show that under air-dried conditions (ca. 40 per cent r.h.) the predominant Cu(II) species present, whether on internal or external sites, is the planar Cu(H2O)2+4 ion. The symmetry axis of the ion is oriented perpendicular to the a-b plane of the silicate sheets. In the presence of a full partial pressure of water, the Cu(II) ions on the external sites and those which are in expansible interlayers become totally hydrated Cu(H2O)2+6 and tumble rapidly. The Cu(H2O)2+4 ions in non-expansible layers retain their restricted orientation on the silicate surface. Some general conclusions have been drawn regarding the nature of charge distribution in the mineral.
Interlamellar and Multilayer Nitrogen Sorption by Homoionic Montmorillonites
Authors: Knudson M. I. , McAtee J. L.
Published: September 2006

Nitrogen sorption by various homoionic montmorillonites was studied at 78°K. The adsorption isotherms in the relative pressure range P/P0= 0.05-0.25 were found to be either Type I or Type II in the BET classification. The nitrogen sorption process was considered to be predominantly interla-mellar when described by a Type I isotherm. With a Type II isotherm, the adsorption was assumed to be predominantly on those surfaces not in the interlamellar regions.

It was concluded that only cations within a certain size range promote significant interlamellar nitrogen penetration in montmorillonites. The role of the smaller cations in nitrogen sorption by montmorillonites seems to be their influence on the external aggregate structures. Very large cations tend to clog up the interlamellar pores as well as some of the external voids.
Properties of ‘Swelling’ Chlorite in Some Mesozoic Formations of California
Authors: Post J. L. , Janke N. C.
Published: September 2006

Slaty strata and their weathering products comprise a large portion of the geologic formations of the western foothills in the Sierra Nevada, Mid-Northern California. The weathering products of Mesozoic slates in particular, locally known as ‘swelling’ chlorites, have caused numerous problems in road construction.

A typical stratigraphic section of slates, which includes ‘swelling’ chlorites, is given for the area of Chili Bar, California, as part of the general geology of the western foothill formations. Remolded slate densities were observed to decrease while measured swelling pressures increased with increasing slate alteration. Swelling pressures in excess of 12.5 psi were observed. Curves are presented in comparison with DTA results showing the effect of alteration on the slate.

The results of X-ray diffraction analyses, in correlation with i.r. data, show a typical slate mineral composition for unaltered material of about one-half chlorite with the remainder being about equal portions of muscovite and quartz. The entire chlorite content of the altered slate becomes a regular mixed-layer clay mineral, corrensite, which has been observed to alter to sedimentary vermiculite and Mg-saponite in residual soil. An i.r. absorption peak at 3690 cm-1 characterizes the mixed-layer clay mineral. Heat treatment of the mixed-layer clay mineral structure reduces the 14.3 Å basal spacing to 11.8Å at 540°C, which decreases to 10.6Å at 850°C, disappearing by 1050°C. Procedures are given for direct quantitative analysis of these three-phase mineral systems using simultaneous linear equations.

Evidence is presented for the alteration minerals formed during weathering of the slate, including Fourier analysis of the mixed-layer clay structure.
Factors Affecting Selected Area Electron Diffraction Patterns of Micas
Authors: Güven Necip
Published: September 2006

Major factors affecting the selected area electron diffraction (SAD) patterns of micas are: lattice properties of the crystal, specimen thickness, orientation of the crystal, properties of the Ewald sphere for electron diffraction, depth of field of the objective lens, and variations in focusing conditions of this lens. Depending on these factors, SAD patterns of 2M1 muscovite may display different symmetries. Specimen ’finite’ thickness affects the intensity in terms of the ’interference function’. The latter function has been evaluated exactly and the intensity distribution has been calculated along the (hk) rows. The observed intensity variations of (hk) spots indicate that the focusing conditions of the objective lens are rather critical for the symmetry of SAD patterns.
A Comparative Study of Simulated and Natural Weathering of Some Oklahoma Shales
Authors: Laguros J. G. , Kumar Subodh , Annamalai M.
Published: September 2006

Shales from six locations in Oklahoma were subjected to natural weathering for 2 yr. Simulated weathering of these shales was effected in the laboratory by subjecting them to ultrasonic treatment in a tank type device. Both treatments produced disaggregation. X-ray diffraction patterns for the ultrasoni-cally treated and weathered shales indicated no major changes in the types of clay minerals. However, natural weathering in the field produced degradation of the clay minerals in addition to disaggregation of the shales. Ultrasonic treatment appears to be a good predictive test for determining the durability and weatherability of the shales; however, it can simulate field weathering only so far as the engineering index properties of the shale are concerned. It is not a predictive test where the mineralogical characteristics are of significance.
Crystal Imperfections with Regard to Direction in Kaolinite Mineral
Authors: Williams D. G. , Garey C. L.
Published: September 2006

The crystallite sizes in the particles from four fractions of a kaolinite-clay were determined from the broadening of the X-ray diffraction lines. Measurements were made of the <002> and <111> planes whose crystallographic directions correspond to the clay plate thickness and diagonal, respectively. The extent of crystal imperfection was determined by comparing the calculated crystallite size with the mean size based on measurements from electron micrographs. The crystal imperfections were found to be more extensive in the plate diagonal, <111>, than in the plate face, <002>, directions. Electron micrographs of hydrofluoric acid-etched samples revealed plate-edge and plate-face imperfections. The latter show a regularity suggesting a mosaic-like texture in the plate surface. Surface imperfections probably have significant influence on the dispersion and flocculation behavior of kaolinite.
Electrolyte Concentration-Permeability Relationships in Sodium Illite-Silt Mixtures
Authors: Hardcastle James H. , Mitchell James K.
Published: September 2006

To examine the effects of clay swelling and dispersion on electrolyte concentration-permeability relationships of low clay content soils, flow experiments were conducted on a silt of fixed particle size distribution containing 0, 5, 7·5, 10 and 15 per cent clay (sodium illite, 2 μm fraction). Flocculated specimens were sedimented using both slow and rapid procedures. After compression each specimen was permeated successively with electrolyte solutions which caused (1) swelling of the clay fraction (0·10 N), and (2) dispersion (0·05 N). Absolute permeabilities varied with clay content, sedimentation procedure, compression rate, and electrolyte concentration; however, the form of this variation plotted against through-put volume was similar for all specimens containing electrolyte solutions causing only swelling of the clay. Increasing the hydraulic gradient above a critical value apparently increased the swelling slightly as evidenced by further reductions in permeability. The permeability of mixtures permeated with electrolyte solution causing dispersion of the clay was more complex and depended on clay content, the hydraulic gradients used to introduce the dispersing electrolyte solution and the pre-dispersion gradients to which the specimens had been subjected. Permeability decreases were attributed to the last stages of swelling prior to dispersion and to pore plugging. Increases in permeability were the result of erosion of dispersed particles. Specimens previously subjected to the highest gradients while swelling dispersed more rapidly and had a greater tendency to erode. The effects of predispersion gradients diminished with increasing clay contents. It is concluded that both compositional and mechanical factors play an important role in determining electrolyte concentration-permeability relationships for soils containing active clay minerals.
Electron-Optical Investigations on Montmorillonites—I. Cheto, Camp-Berteaux and Wyoming Montmorillonites
Authors: Güven Necip
Published: September 2006

Other layer silicates are consistently present as impurities in natural montmorillonite samples. They have a distinctly different morphology from the common montmorillonite particles. The selected area electron diffraction (SAD) of these impurities display unusually sharp spot patterns with triclinic, monoclinic and hexagonal symmetries. These impurities are most likely micas, which are easily detectable with X-rays in the coarser fractions (> 10 μm) of the samples.

The crystal structure model with the space group C2 for montmorillonite single layer has an unusual configuration of OH’s and vacancies for a dioctahedral layer silicate. Our intensity calculations do not bring a conclusive evidence for distinguishing the two possible space groups C2 and C2/m on the observed SAD patterns of montmorillonite.

The SAD of the thin montmorillonite flakes in Cheto, Camp-Berteaux and Wyoming samples display uniform ring, circular arcs and spotty ring patterns, respectively. These patterns indicate different modes of association of crystallites or different arrangements of elementary layers within them.
Phosphate Transport in Illite Due to Consolidation
Authors: Moore Charles A. , Zouestiagh Nahid
Published: September 2006

The conditions were studied under which consolidation loading caused the release of phosphate from a saturated illite clay. P32 tracer techniques were employed to follow the movement of phosphate in composite samples composed of tagged and untagged portions. The samples, initially consolidated to 1·0 kgcm−2 stress were reconsolidated to 0·1, 0·5, 2, 4 and 8 kg cm−2 stress and the transport of phosphate was monitored by counting the radioactivity of 0·01-in. thick sections sliced parallel to the major principal plane. Corrections were applied for P32-P31 self-diffusion. It was found that: (1) for low phosphate concentrations there was no observable transport due to consolidation type flow: (2) for high phosphate concentrations and for stresses less than or equal to the preconsolidation load there was no observable transport due to consolidation type flow; and (3) for high phosphate concentrations and for loads above the preconsolidation load there was detectable transport of phosphate, presumably due to the consolidation flow. A mechanism based on self-diffusion plus uniform flow was able to semi-quantatively explain the test results.
Experimental Transformation of a Chlorite Into a Vermiculite
Authors: Ross G. J. , Kodama H.
Published: September 2006

An orthochlorite (sheridanite) was heated to 610°C to dehydroxylate the hydroxide sheet and to oxidize ferrous iron. The heated sample was shaken for 20 min in a mixed solution of 0·2 N HCl and 0·2 N NaCl to dissolve the dehydroxylated hydroxide sheet. X-ray diffraction, thermal, infrared absorption and chemical analyses showed that the resulting product was similar to Kenya vermiculite. The procedure shows promise for the individual determination of the composition of the hydroxide sheet and of the mica layer in the chlorite structure. The experiments indicate that the hydroxide sheet in orthochlorites must be structurally disturbed before it can be selectively removed. In nature, structural disorganization of the hydroxide sheet of chlorite by dehydroxylation and oxidation of ferrous iron might occur during meta-morphic processes, and chlorite to vermiculite transformation could take place during subsequent acid weathering. In pedogenic weathering conditions it is likely that oxidation of ferrous iron plays a major role in initiation of the structural disorder required for the selective removal of the hydroxide sheet in the weathering of chlorite to vermiculite.
Electro-Optic Investigation of the Permanent and Induced Dipoles of Montmorillonite as Affected by Electrolyte Concentration
Authors: Schepers J. S. , Miller Raymond J.
Published: September 2006

An electro-optic birefringence technique was employed to study the orientation mechanism of montmorillonite in an electric field. The instantaneous reversal of the field polarity produced evidence of a low voltage permanent dipole and a high voltage induced dipole. This technique was used to study theeffect ofelectrolyte concentration on the rotational diffusion coefficient, a measure of the rate at which the particles rotate or relax, within the solution, from a preferred orientation. Thus, a measure of the immediate environment of the particles was obtained that is not an average effect for the whole system, yet allows for the full development of the clay-cation-water interactions under the experimental conditions. It was found that particle rotation could be accounted for using the measured particle size and normal water viscosity only when the double layer was fully developed, with no free ions or other perturbations. As soon as perturbations were applied, either by adding salts or applying an electric field, the measured particle size and normal viscosity would not account for the data. Either the rotating moiety has to be larger, that is, be a particle plus a water hull, or the viscosity greater, or in some cases both.
Artificial Alteration of Biotite Into a 14 Å Layer Silicate with Hydroxy-Aluminium Interlayers
Authors: Nagasawa K. , Brown G. , Newman A. C. D.
Published: September 2006

Biotite was altered by boiling in 0.2 M A1C13 solution, and the products were examined by X-ray powder and single-crystal diffraction, chemical analysis and thermogravimetry. The altered material is a 14 Å clay mineral with hydroxy-Al interlayers. It has a stacking sequence characteristic of vermiculite and its silicate layers are similar in chemical composition to trioctahedral vermiculite. The results of extracting the interlayer material with sodium citrate solution, X-ray examinations after heating and thermogravimetry show that the interlayer material is composed of Al associated with OH and H2O. The chemistry and kinetics of the alteration reaction and the orientational between the altered and original biotites are also discussed.
Exchangeability of Potassium in Heated Fine-Grained Micaceous Minerals
Authors: Smith S. J. , Scott A. D.
Published: September 2006

Samples of several naturally fine-grained micaceous minerals were heated at 450°C for 24 hr (after the effects of other temperatures and heating periods were evaluated with the < 2 μm fraction of Grun-dite) and then characterized in terms of their release of K to NaCl-NaTPB (sodium tetraphenylboron) solutions and other potentially related properties.

This heat treatment produced a substantial increase in the amount of K that each mineral released when first placed in the NaCl-NaTPB solution (the greatest increase being 22 m-equiv K/100 g in Marblehead illite). Depending upon the mineral heated, the subsequent rate of K release was increased, decreased or unchanged. Also, all the minerals except glauconite exhibited an increase (ranging from 4 to 38 m-equiv K/100 g) in their maximum degree of K release if they were heated. Thus, it was established that the K release behavior of these minerals is not only subject to appreciable alteration by heat treatments but is altered in a manner that varies with the mineral. The nature of these alterations, however, did not clearly identify an involvement of the other mineral properties that were examined. An increase in NH4- and Cs-exchangeable K occurred when these minerals were heated—presumably as a result of exfoliation. With Morris illite samples, this increase was nearly 28 m-equiv 100 g. Thus, heated samples of these minerals may be useful sinks for the removal of NH4 and Cs in various wastes.
Contributions of Forest Opal and Associated Crystalline Phases to Fine Silt and Clay Fractions of Soils
Authors: Wilding L. P. , Drees L. R.
Published: September 2006

The scanning electron microscope (SEM) is useful in the identification of biogenic opal. Opaline spheres, cups, and scrolled or convoluted sheets were identified in both soil and vegetative isolates. X-ray diffraction analysis indicates that both alpha quartz and cristobalite were co-associated with the amorphous opaline phase synthesized during life metabolism of deciduous tree leaves. Such crystalline phases were most abundant in the 2–5 μm fraction and many consist of anitsotropic rods with parallel extinction or equidimensional bodies with aggregate extinction. Between 2/3 and 3/4 of the total opal isolate from deciduous tree leaves was solubilized when digested for 2–5-min in boiling 0.5 N NaOH. Rate of dissolution was a function of particle-size and tree species. Biogenic opal of forest origin was about 10–15 times more soluble than grass opal, which probably reflects the higher specific surface of the former.
Use of Long-Spacing Alcohols and Alkanes for Calibration of Long Spacings from Layer Silicates, Particularly Clay Minerals
Authors: Brindley G. W. , Wan Hsien Ming
Published: September 2006

Lattice spacings of layer silicates, particularly clay minerals, may exceed 20 Å. The errors in measuring lattice spacings increase rapidly for spacings greater than about 10 Å and diffraction angles 2θ less than about 10°. Long-chain organic compounds, such as normal alcohols, C14–C20, and normal alkanes (paraffins), C26–C30, provide useful calibrations for lattice spacings in the range 10–50Å. The basal spacings of the calibrating substances are determined from their higher order reflections in the angular range where reflections from quartz and silicon are used as standards.
Diagenesis of Clay Minerals from Lower Cretaceous Shales of North Eastern British Columbia
Authors: Foscolos A. E. , Kodama H.
Published: September 2006

Clay minerals from shale outcrops of the Lower Cretaceous Buckinghorse Formation (4250 ft thick) were investigated in order to assess their degree of diagenesis and their oil-generating potential. Crystallinity index, sharpness ratio, per cent of illite which is the 2M polymorph and presence of discrete minerals have been studied in the whole clay fraction, while the very fine clay fraction has been subjected to X-ray diffraction, differential thermal, thermogravimetric, differential thermogravimetric, i.r. spectroscopy, surface area and chemical analyses. With information derived from these studies and from published data, a classification scheme was devised which relates variation of clay mineralogy to diagenetic stages and burial depth.

Data on the < 2 μm size fraction show that the crystallinity index decreases while the sharpness ratio and per cent of illite which is the 2M polymorph increase with burial depth. Results on the <0·08 μm fraction reveal that a three-component interstratified clay mineral exists. In addition, Fourier transform calculations and chemical and physicochemical analyses indicate that both the ratio of the amounts of non-hydrated clays (illite) to hydrated clays and the K2O content of clays increase with burial depth; cation exchange capacity and surface area decrease with burial depth.

Based upon a classification scheme, which was devised by combining criteria and data derived from the studies of Weaver (1961a), Kubier (1966), Burst (1969) and Dunoyer de Seconzac (1970), the upper and middle parts of the formation (upper 3250 ft) fall within the middle stage of diagenesis whereas the lower part (1000 ft) is allocated to the beginning of late diagenesis. In terms of Burst’s (1969) work, the upper 3250 ft are transitional between the stability and dehydration zones indicating that, prior to uplift, hydrocarbons may have been in the process of migration. The lower 10000 ft of the formation are in the restricted dehydration zone, indicating that hydrocarbon migration should have been completed.
Comparative Studies on Extraction of Sediment Interstitial Waters: Discussion and Comment on the Current State of Interstitial Water Studies
Authors: Manheim F. T.
Published: September 2006

The implication by Murthy and Ferrell (1972) that interstitial water studies are in a confused state is criticized on the basis that the authors have not drawn on a considerable body of data, especially Soviet studies since the 1950’s, and results of the Deep Sea Drilling Project. Pressure filtration systems for extracting interstitial waters are currently the methods of choice for marine studies and have achieved substantial reliability and reproducibility. Although gaps and problems remain, many aspects of interstitial composition of marine sediments have been clarified; these include the substantial constancy of composition of interstitial waters in deep sea pelagic deposits, depletion of interstitial cations owing to authigenic mineral formation in more rapidly accumulated (especially terrigenous) sediments, and special phenomena in sediments overlying salt deposits.
Effect of Oxidation and Reduction on Potassium Exchange of Biotite
Authors: Ross G. J. , Rich C. I.
Published: September 2006

The selectivity of K over Ca of Amelia biotite increased sharply upon oxidation by H2O2 at pH 6·0. This increase in K selectivity was only partially reversible upon reduction by Na2S2O4. Oxidation by H2O2 of the Ca-form of this biotite resulted in a loss of no more than 2·8 and 0·4 per cent of the total Fe and Al, respectively, and caused a small and perhaps insignificant decrease in layer charge. Although 95 per cent of the structural Fe2+ of the Ca-form of this biotite was ozidized by H2O2, only 17 per cent was reduced again by four treatments with Na2S2O4.

The evidence indicates that under the conditions of this experiment the loss of protons from structural hydroxyls was the dominant mechanism by which electroneutrality in the biotite was maintained during oxidation of structural Fe2+. Because this mechanism increases the bond strength of interlayer K, it explains the increased K selectivity of biotite upon H2O2 oxidation. The relatively small reduction by Na2S2O4 of structural Fe3+ to Fe2+, which implies an equally small reprotonation of structural hydroxyls, explains the incomplete reversibility of K selectivity by Na2S2O4 treatment.
Quantitative Clay Petrology: The Trees but Not the Forest?
Authors: Towe Kenneth M.
Published: September 2006

Gravitational settling and centrifuge techniques have been criticized in the preparation of X-ray specimen mounts for quantitative clay petrology because of the marked mineral segregations that can occur. Although the same factors can operate to produce error in the separation of the traditional less-than-2-μm fraction, this potentially more important source of bias is seldom taken into consideration. A fair representation of the bulk sample deserves at least as much attention as a representative X-ray mount. The most accurate and precise X-ray analyses may be geologically misleading or meaningless otherwise and translate as exercises in precision for its own sake.
The Heterogeneity of the Charge Density in Montmorillonites
Authors: Stul M. S. , Mortier W. J.
Published: September 2006

The heterogeneity of the interlayer cation density and the corresponding mean layer charge density due to isomorphous substitution have been determined for six montmorillonite samples. This has been achieved by considering the transition of a monolayer to a double layer complex with alkylammonium ions. The transition is related to the interlayer cation density, together with the variation of the apparent spacings, which in turn is related to the composition of this two-component mixture.

All the samples showed a heterogeneous interlayer cation distribution and a differing mean charge density.
Fabric-Property Relationships in fine Granular Materials
Authors: Mahmood Arshud , Mitchell James K.
Published: September 2006

In this investigation fabric-property relationships were studied in a silty fine sand sized crushed basalt—an artificial ‘soil’ that has previously been used to simulate lunar soil. The fabric was characterized by measuring preferred orientations of grains, and pore size distribution was determined by mercury intrusion porosimetry. When deposited by pouring, the grains acquired strong preferred orientations in the horizontal direction and formed pores between 1 and 30 μm dia. Densification by static or dynamic compaction resulted in near random grain arrangement and pore sizes between 0·1 and 10 μm dia.

Strength in direct shear and one-dimensional compressibility with the associated lateral stresses were measured. The strength was up to 30 per cent higher when the sample was sheared normal to the preferred orientation of grains than when the shearing was parallel to the orientation direction. This is to be expected, as shearing across the preferentially oriented grains should involve breakage or reorientation of many grains. At a given initial void ratio the compressibility of statically compacted specimens was larger (up to 30 per cent higher axial strain) than that of dynamically compacted specimens at very low stresses. At higher stresses both samples exhibited equal compressibility, suggesting that the grains become more randomly arranged at low void ratios (comparing samples of equal initial void ratios).
Adsorption and Transformation of HCN on the Surface of Copper and Calcium Montmorillonite
Authors: Cruz M. , Kaiser A. , Rouxhet P. G. , Fripiat J. J.
Published: September 2006

Adsorption isotherms of HCN by Cu- and Ca-montmorillonites show that water present in the interlayer space decreases HCN adsorption.

For Ca-montmorillonite, i.r. spectra permit distinguishing between HCN interacting with the cations and molecules filling the interlayer space. Both types are removed upon outgassing. The residual water is not displaced by HCN.

On Cu-montmorillonite, species (presumably CN− ions) strongly held by the cations are observed in addition to adsorbed HCN molecules. The residual hydroxyls retained in the interlayer space are removed by the adsorption of HCN. These hydroxyls, either OH− or H2O, are characterized by two well defined stretching bands.

Infra-red spectra of samples heated below 200°C show that adsorbed HCN is involved in chemical reactions. For both clays, bands appear in the region characteristic of carbonyl and carboxyl groups; the production of ammonium is detected for Cu-montmorillonite. The reactions and the observed spectral features could be accounted for by the formation of formamide.
Aqueous Dissolution Studies of Illite Under Ambient Conditions
Authors: Reesman A. L.
Published: September 2006

Dissolution data on five of the six illites reported by Reesman and Keller (1968) indicate that these illites are more stable than was previously thought. The revised Gibbs free energies of formation (ΔGf0) with respect to the ‘ideal’ illite formula and the muscovite formula are

Use of muscovite formula as an indirect comparator provides a means of predicting the relative stabilities of these chemically complex materials.

The response of illite-equilibrated solution to a kaolin ΔGf0 was found in all samples in which a 7 Å mineral phase was detected by X-ray diffraction. Stability diagrams based upon the ΔGf0 with respect to ideal muscovite and kaolin formulas show a rather wide range in chemical conditions through which illites and kaolin minerals with differing ΔGf0 would be stable. However, in carbonate rocks and sea water illite is stable relative to kaolin. During the weathering of carbonates the lower pH zones in the clay-rich residuum above the carbonates favor the transformation of illite to kaolin minerals.