bluuebunny/crossref_metadata_2025 huggingface dataset:
Reactions of Clay Volatiles with n-Alkanes
Authors: Heller-Kallai Lisa , Miloslavski Irena , Aizenshtat Zeev
Published: August 2006

Volatiles formed on heating clay minerals contain a variety of cations and anions and are highly reactive. Gas chromatograph-mass spectrometer analysis of long-chain n-alkanes exposed to such volatiles showed that some decomposition occurred even <250°C. Reactions with anions donated by the volatiles led to compounds containing atoms other than C and H, e.g., Cl. The products obtained from n-alkanes heated in a stream of clay volatiles to 500°C resembled those produced by corresponding alkane-clay mixtures heated to 250°C. At higher temperatures contact between the alkanes and montmorillonite or halloysite led to changes in the assemblages formed, whereas kaolinite or sepiolite had no effect. Thus, the first reactions that occurred when clays were heated with n-alkanes were apparently induced by the volatiles; at higher temperatures catalysis due to direct contact came into play with some of the clay minerals.
Effects of Relative Humidity on the Basal Expansion of Mg-Smectite Equilibrated with Ethylene Glycol at Low Vapor Pressure
Authors: Hsieh Y. P.
Published: August 2006

The effects of relative humidity (RH) on the expansion of Mg-smectite, equilibrated with low vapor pressure of ethylene glycol (EG), was studied. Four smectite samples were equilibrated with EG vapor from: (1) saturated vapor of pure EG, (2) an EG-CaCl2 solvate, and (3) 0.05 relative EG vapor pressure at 65°C. X-ray powder diffraction (XRD) analyses of the clays under different RH conditions indicated that without EG, the basal spacing of Mg-smectite samples could only be expanded to 16 Å, even at 0.97 RH. The basal spacing of Mg-smectite samples equilibrated with saturated EG vapor was expanded to 17.1 Å and was not significantly affected by RH in the range 0.1–0.9. The basal spacing of the Mg-smectite samples equilibrated with vapor from the EG-CaCl2 solvate and 0.05 relative EG pressure at 65°C was expanded by an amount that depended on the RH during the XRD analysis. The basal spacing increased from 14.2 to 17.1 Å as the RH increased from 0.6 to 0.75, except for sample API 23, which expanded to 17.1 Å at RH > 0.9. This sample did not expand beyond 16 Å when it was equilibrated with 0.05 EG relative vapor pressure. Sorption of moisture from air caused the one-layer EG-Mg-smectite complex (basal spacing = 14.1 Å) to rearrange itself to a double-layer EG-Mg-smectite complex (basal spacing = 17.1 Å). A small amount of the adsorbed EG in Mg-smectite, much less than was needed to cover a one-layer of the interlayer surfaces, caused an expansion of the basal spacing to 17.1 Å at high RH during the XRD analysis. The minimum amount of adsorbed EG which caused the one-/two-layer EG complex conversion was about 20–30 mg EG/g. The conversion was fast (<5 min) and was relatively reversible.
Mechanisms of Palygorskite and Sepiolite Alteration as Deduced from Solid-State 27Al and 29Si Nuclear Magnetic Resonance Spectroscopy
Authors: Komarneni Sridhar
Published: August 2006

The mechanisms of palygorskite and sepiolite alteration to smectite under mild hydrothermal conditions were investigated by solid-state 27Al and 29Si magic-angle spinning-nuclear magnetic resonance (MAS-NMR) spectroscopy, X-ray powder diffraction (XRD) and transmission electron microscopy (TEM). Palygorskite altered to smectite in the presence of NaOH at 150°C. 27Al MAS-NMR spectroscopy showed that the Al coordination changed from chiefly octahedral in palygorskite to chiefly tetrahedral in the smectite product. 29Si MAS-NMR spectroscopy showed that the nearest neighbor environment of Si also changed when palygorskite altered to smectite. The XRD data showed that the synthetic smectite is trioctahedral in nature with tetrahedral charge. The TEM results revealed that the needle-like morphology of palygorskite was preserved in the product smectite. The MAS-NMR results in conjunction with the above XRD and TEM studies suggest that the mechanism of palygorskite alteration was a dissolution and recrystallization process rather than a solid-state reorganization to form 2:1 layer silicate units from the preexisting chain structure. Sepiolite altered to smectite in the presence of 2 N salt solutions at 300°C. The trioctahedral nature of the product smectite as detected by XRD and the foil-like morphology of product smectite as shown by TEM suggest that the mechanism of sepiolite transformation to smectite was also a dissolution and recrystallization process. The tetrahedral Al coordination detected by 27Al MAS-NMR in the smectite altered from sepiolite corroborated the XRD and TEM results.
Effect of Hydrostatic Pressure on the Swelling of n-Butylammonium Vermiculite
Authors: Smalley M. V. , Thomas R. K. , Braganza L. F. , Matsuo T.
Published: August 2006

The osmotic swelling of an n-butylammonium vermiculite in a 0.1 M solution of n-butylammonium chloride has been studied as a function of temperature and hydrostatic pressure by neutron diffraction. On application of a pressure of 1050 bar the vermiculite swelled macroscopically at 20°C, the c-axis spacing changing from 19.4 to 126 Å. The phase transition was completely reversible with respect to both pressure and temperature, and a complete study of the temperature-pressure phase diagram was made at pressures as high as 2000 bar. The heat capacity change with temperature across the swelling transition was measured at atmospheric pressure, and the enthalpy and entropy of the change from crystalline to osmotic phases were found to be, respectively, 5.2 J/g and 0.0183 J/K·g of dry clay. The combination of the entropy change with the gradient of the pressure-temperature phase boundary gave the volume change accompanying the transition. The total volume of the swollen phase was less than that of the crystalline phase plus the appropriate amount of solution, corresponding to a fractional decrease of about 0.1% in the water volume from bulk solution to between the plates.
Effect of Cysteine and Manganese on the Crystallization of Noncrystalline Iron(III) Hydroxide at pH 8
Authors: Cornell R. M. , Giovanoli R. , Schneider W.
Published: August 2006

To provide a greater understanding of the crystallization of iron oxides under natural aqueous conditions, the combined effect of an inorganic ion (Mn2+) and a reducing organic ligand (L-cysteine) on the conversion of noncrystalline ferric hydroxide to goethite and/or hematite was investigated at pH 8.

At cysteine: Fe ratios ≥ 0.2, L-cysteine caused noncrystalline iron(III) hydroxide to transform rapidly into goethite at pH 8; in the absence of the organic ligand, hematite was the predominant reaction product. The presence of Mn (≥9 mole %) in the cysteine-ferric hydroxide system retarded crystallization and reduced the goethite-promoting effect of cysteine.

Polarographic measurements showed that the adsorption of cysteine on noncrystalline iron(III) hydroxide was immediately followed by the oxidation of cysteine to the disulfide with simultaneous reduction of a proportion of the interracial ferric ions. The partly reduced noncrystalline iron(III) hydroxide dissolved at pH 8 more rapidly than the original material, thus facilitating the formation of goethite. In Mn(II)-noncrystalline iron(III) hydroxide coprecipitates, the interfacial oxidation/reduction reaction with cysteine (and hence the partial reduction of the noncrystalline phase) was reduced, due to replacement of some interfacial Fe(III) by non-reducible Mn.

At pH 8, uptake of Mn by crystalline iron oxides was low (< 5 mole %). Mn precipitated preferentially as pure Mn phases, either rhodochrosite (in NaHCO3 buffer) or hausmannite (in NH4Cl/NH3 buffer).
Mineral Assemblages of Volcanic and Detrital Partings in Tertiary Coal Beds, Kenai Peninsula, Alaska
Authors: Reinink-Smith Linda M.
Published: August 2006

Volcanic and non-volcanic partings are exposed in coal beds of the Tertiary Beluga and Sterling Formations along the shores of the Kenai lowland, Alaska. About two-thirds of the partings originated as air-fall tephra which fell in coal-forming swamps. The tephra partings in the Pliocene strata are unaltered or slightly altered and have a characteristic mineral assemblage of volcanic glass ± montmoriUonite ± kaolinite ± opal-CT. Miocene strata are slightly altered to totally altered, and a typical mineral assemblage consists of feldspar ± kaolinite ± montmorillonite ± quartz ± crandallite ± altered volcanic glass. Crandallite appears to have formed early in diagenesis by the replacement of volcanic glass prior to the formation of montmorillonite and kaolinite.

About one-third of the partings originated primarily as detrital sediments derived from surrounding metamorphic and sedimentary terranes and were deposited by periodic floods. Mixtures of tephra and detrital sediments were also noted and were difficult to distinguish from tephra partings in the field. Detrital partings are characterized by detrital chlorite + illite + smectite + quartz ± feldspar ± siderite ± kaolinite. The chlorite in these strata is allogenic. Smectite is less common in the detrital partings.
DLVO and Non-DLVO Interactions in Hectorite
Authors: van Oss C. J. , Giese R. F. , Costanzo P. M.
Published: August 2006

The Derjaguin-Landau-Verwey-Overbeek (DLVO) theory sums the attractive van der Waals and repulsive electrostatic forces as a function of separation distance to predict the interaction between charged particles immersed in a liquid. In aqueous media, however, non-electrostatic polar (electron acceptor/electron donor or Lewis acid/base) forces between particles with high energy surfaces often are comparable to, or greater than, the components of DLVO theory. By means of contact angle measurements on smooth self-supporting clay films, the values of the polar surface forces (AB) and the van der Waals forces (LW) of hectorite were measured. Determinations of ζ were used to derive the electrostatic forces (EL). Calculations based on the values obtained for the EL, LW, and AB forces show that for smooth spheres with a radius of 1 µm in a ≥ 0.1 M NaCl solution a net attraction exists leading to flocculation. At NaCl concentrations of ≤ 0.01 M, a repulsion energy of about +500 to +1300 kT exists at separation distances ≤ 50 Å, preventing contact between particles, thus ensuring stability of the colloidal suspension. At these concentrations, theory predicts that small clay particles or edges of clay crystals having an effective radius of curvature ≤ 10 Å should be energetic enough to overcome the repulsion barrier which prevents flocculation. Experimentally, for NaCl solution concentrations of ≥ 0.1 M, suspensions of hectorite particles flocculated, whereas at concentrations of ≥ 0.01 M, the suspensions remained stable. These experimental results agree with the predictions made by summing all three forces, but contradict the calculations based on classical DLVO theory.
Formation of Trioctahedral Illite from Biotite in a Soil Profile over Granite Gneiss
Authors: Fordham A. W.
Published: August 2006

Clay fractions separated from the A2, B, and C horizons of a soil formed on granite gneiss showed X-ray powder diffraction (XRD) spacings characteristic of trioctahedral illite. The trioctahedral illite was derived from biotite, and its development through various stages of weathering was followed by optical and electron microscopy combined with electron microanalysis. In the initial stages of weathering, Fe2+ within biotite was oxidized, without the loss of much K. During this process, biotite flakes became slightly buckled and fractured. Solutions moved into the damaged flakes leading to chemical weathering and exfoliation along cleavages and angular fractures. Major exfoliation broke up the flakes into segments, which themselves contained minor exfoliations and alterations along cleavage planes. The extent of exfoliation and alteration continued until thinner and shorter segments consisted almost wholly of thin (< 0.25 µm), parallel wafers separated by less compact layers of particles and microaggregates. The segments finally lost their shape and divided into clay-size particles. Parts of the thin wafers had the same chemical composition (and structure) as the original, intact flakes of oxidized biotite. The same parts of wafers retained some of the optical properties of the original biotite, and, when broken down to clay, they produced the XRD spacings of 10 and 1.54 Å, typical of fine-grained, trioctahedral mica (illite).
The Influence of Aluminum on Iron Oxides. XV. Al-for-Fe Substitution in Synthetic Lepidocrocite
Authors: Schwertmann Udo , Wolska Emilia
Published: August 2006

Lepidocrocite samples, γ-FeOOH, containing 0–10 mole % Al-for-Fe substitution were synthesized at 15°C and pH 8 by oxidizing mixed FeCl2-AlCl3 solutions. The unit-cell parameters a, b, and c were measured from step-counted X-ray powder diffractograms using seven lines and Si as an internal standard. With increasing Al substitution from 0 to 10 mole % the unit-cell edge lengths a, b, and c decreased regularly by 0.3, 0.8, and 0.6%, respectively. Furthermore, the crystals became smaller, but gained in thermal stability. Decrease in crystal size parallel to the y axis led to a significant increase of the OH-stretch vibration and a decrease of the out-of-plane OH-bending vibration due to a weakening of the hydrogen bond between the zig-zag layers in the structure.
Reactivity of Anisoles on Clay and Pillared Clay Surfaces
Authors: Carrado Kathleen A. , Hayatsu Ryoichi , Botto Robert E. , Winans Randall E.
Published: August 2006

Pillared bentonites were found to be efficient catalysts for the O-methyl bond cleavage of anisoles (e.g., m-methylanisole, guaiacol, and creosol) under very mild, static conditions (150°C, a few hours, inert atmosphere). The O-methyl bond cleavage led to phenolic products. Gas chromatographymass spectrometry and solid-state 13C nuclear magnetic resonance (NMR) techniques used to probe 13C-labeled anisoles revealed that dealkylation and transalkylation reactions occurred to a large extent, and that conversion was efficient at >95% after two days. Ortho- and para-isomers were observed exclusively, without any evidence of meta-substitution. Volatile products were determined by mass spectrometry to be 13CH3OH and (13CH3)2O. Magic-angle spinning 13C NMR experiments showed that the molecules were fairly mobile in the clay micropores prior to catalysis. After catalysis, cross-polarization NMR showed that molecular motion had decreased markedly. Ultraviolet-visible spectroscopy of the colored complexes suggested some quinone formation. The trend of clay reactivity was found to be: pillared bentonite ≫ acid-washed montmorillonite > untreated bentonite > pillared fluorhectorite ≃ untreated fluorhectorite.
Far-Infrared Study of Potassium in Micas
Authors: Prost R. , Laperche V.
Published: August 2006

The characterization of cations associated with clay materials has generally been approached by the sequential use of specific chemical reagents. To avoid the disturbing effect of the chemical reagents on the state and location of compensating cations of clays and to get information in situ, far-infrared spectroscopy was used. The far-infrared vibrational spectra of the potassium cation in muscovite, phlogopite, and biotite were recorded before and after heating at the dehydroxylation temperature. The vibrational frequency of K in micas before dehydroxylation was found to be a function of the di- or trioctahedral character and of the Fe content. After dehydroxylation or deprotonation, shifts of the K absorption band to lower frequencies were observed for the heated muscovite, in which K exchangeability increased, and to higher frequencies for the heated biotite, in which K exchangeability decreased. These results suggest that the vibrational frequency of potassium is characteristic of the state of K in these minerals and of its ability to be exchanged.
Characterization of Synthetic Na-Beidellite
Authors: Kloprogge J. Theo , Jansen J. Ben H. , Geus John W.
Published: August 2006

Na-beidellite, a member of the smectite group, was grown hydrothermally from a gel of composition 0.35Na2O·2.35Al2O3·7.3SiO2 in NaOH solutions at a pH between 7.5 and 13.5, a pressure of 1 kbar, and a temperature of 350°C. The synthetic Na-beidellite was characterized by means of scanning electron microscopy, X-ray powder diffraction, infrared spectroscopy, electron microprobe, inductively coupled plasma-atomic emission spectroscopy, and thermogravimetric analysis. The unit-cell parameters of the orthorhombic cell are: a = 5.18, b = 8.96, and c = 12.54 Å. The cation-exchange capacity was determined to be 70 meq/100 g. A maximum of 40 wt. % water was present and reversibly lost by heating to about 55°C. The loss of water caused a decrease of the basal spacing to 9.98 Å. At temperatures ≥600°C, the Na-beidellite started to dehydroxylate, reaching its maximum in the range 600°–630°C. At 1100°C the remaining solid recrystallized to Al6Si2O13 (mullite) and SiO2 (cristobalite).
Hydrothermal Reactivity of Mixed-Layer Kaolinite/Smectite: Experimental Transformation of High-Charge to Low-Charge Smectite
Authors: Proust D. , Lechelle J. , Lajudie A. , Meunier A.
Published: August 2006

A mixed-layer kaolinite/smectite (K/S) containing trace amounts of quartz, discrete kaolinite, goethite-hematite, and calcite was hydrothermally reacted with deionized water at 150°, 200°, and 250°C for 1 to 12 months. The starting K/S contained 50% smectite consisting of 15% low-charge and 35% high-charge layers. The X-ray powder diffraction and chemical analyses of the reacted products indicated a progressive reaction from high-charge to low-charge smectite as a function of time and temperature. The reaction reached completion after 4 months at 250°C, at which point high-charge smectite layers entirely reacted to low-charge smectite layers, the latter maintaining a constant proportion of about 90% for longer run durations. For long reaction times, discrete kaolinite totally reacted, whereas quartz showed only partial dissolution and iron oxides remained stable. Thus, the reaction of high-charge to low-charge smectite layers may be expressed as: high-charge smectite + kaolinite (both interstratified and discrete component) + quartz → low-charge smectite.
Thermal Stability of Halloysite by High-Pressure Differential Thermal Analysis
Authors: Johnson Sheryl L. , Guggenheim Stephen , Koster van Groos A. F.
Published: August 2006

Platy (Te Puke, New Zealand), cylindrical (Spruce Pine, North Carolina), and spherical (North Gardiner mine, Huron, Lawrence County, Indiana) halloysite samples were analyzed by high-pressure differential thermal analysis (HP-DTA) to determine the effect of morphological and chemical differences on their respective thermal stability. In halloysite, these morphological differences imply structural features. The metastable phase relations of each are analogous to those of kaolinite. At 1 bar, the platy, cylindrical, and spherical samples showed peak temperatures (maximum deflection in the dehydroxylation endotherm) of 560°, 578°, and 575°C, respectively, whereas at about 600 bars the peak temperatures were 622°, 655°, and 647°C. At low pressures the observed reaction is related to dehydroxylation: halloysite (H) metahalloysite (MH) + vapor (V), whereas higher pressures produce melting reactions, either H + V = metaliquid (ML) for conditions of P(H2O) = P(total), or H + MH = ML for P(H2O) < P(total). The PT conditions of the invariant point, H + MH + ML + V, for each system are: Te Puke, 612° ± 4°C, 25 ± 7 bars; Spruce Pine, 657 ± 2°C, 30 ± 7 bars; North Gardiner, 652° ± 2°C, 34 ± 7 bars. The lower thermal stability of the Te Puke sample may be related to its higher iron content, although additional data are necessary to confirm that it is not related also to the platy structure. Furthermore, morphological differences between the cylindrical and spherical varieties appear to have had little effect on the energy required to dehydroxylate these halloysite structures. Exceptionally high values obtained for the dehydroxylation enthalpies using the van't Hoff equation, compared with values derived using other methods, may be explained by a 10–15-bar excess in the intracrystalline H2O fugacity during dehydroxylation. Intracrystalline fugacity is defined here as the H2O fugacity within crystallites and is not related to the partial pressure of H2O around individual particles.
Electrostatic Potential at the Basal (001) Surface of Talc and Pyrophyllite as Related to Tetrahedral Sheet Distortions
Authors: Bleam William F.
Published: August 2006

Maps of the electrostatic potentials at the basal plane of talc and pyrophyllite, computed using a two-dimensional Ewald lattice-sum, reveal the effects caused by structural distortion of the phyllosilicate layer. Rotation and tilting of basal tetrahedra in phyllosilicates dramatically perturb the electrostatic potential near the (001) surface. A potential high exists at the center of each six-fold ring of the talc (001) surface. Concerted counter-rotations of basal tetrahedra by 10°, as are typical in pyrophyllite, cause the potential lows above basal oxygens rotated into the ring to overlap, eliminating the ring-centered potential highs. Expansion of the vacant site in dioctahedral minerals tilts the basal tetrahedra by 4° and moves one-third of the basal oxygens about 0.2 Å toward the center of each phyllosilicate layer and away from the (001) surface, thereby producing corrugations of the basal surface. This shift dramatically reduces the contribution of these displaced basal oxygens to the (001) surface potential. Rotation and tilting of basal tetrahedra may influence the arrangement of interlayer water molecules on smectites and other swelling phyllosilicates by the effect that these distortions have on the (001) surface potential.
Relevance of Different Intercalation Tests for Distinguishing Halloysite from Kaolinite in Soils
Authors: Churchman G. J.
Published: August 2006

The expandabilities of kaolin-group minerals in different horizons in 10 soils from New Zealand and Fiji were measured immediately after the application of formamide and after the sequential application of hydrazine, water, and glycerol (HWG treatment). The expandabilities of these minerals in some of the soil samples with dimethylsulphoxide (DMSO) and after long-term (4-day) formamide treatments were also measured. The abundance of characteristic halloysite shapes was determined from electron micrographs of selected samples. The expandabilities of several non-soil kaolinite samples with the DMSO and HWG treatments were also measured.

The expansion of kaolin-group minerals showed the same trends within almost all profiles, whether determined using formamide (by the immediate-formamide treatment) or glycerol (by the HWG treatment). Except where both treatments led to complete intercalation, the HWG treatment always caused more expansion of kaolin-group minerals than obtained immediately after formamide application. The HWG treatment expanded some non-soil kaolinite samples, but well-crystallized kaolinite was not affected by this treatment. The DMSO treatment expanded kaolin-group minerals in the soils to a similar extent as the HWG treatment and also expanded well-crystallized kaolinite. The degree of expansion resulting from the immediate-formamide treatment matched abundance of typical halloysite particle shapes more closely than the degree of expansion given by the other intercalation treatments. The degree of expansion immediately following formamide application could be diminished, if the samples were heated at 40 ± 5°C.
Preparation and Properties of Pillared Interstratified Illite/Smectite
Authors: Sterte Johan
Published: August 2006

Pillared, regularly and randomly interstratified illite/smectite (I/S) was prepared by interacting aluminum chlorohydrate with I/S in aqueous dispersion. I/S samples from Kinnekulle, Sweden, ranging in composition from 30–60% smectite layers, were used as starting clays. The pillaring resulted in a separation of the smectite layers in the I/S of about 9 Å, as estimated by X-ray powder diffraction and by nitrogen adsorption studies. Only the smectite layers of the clay were modified by the pillaring procedure. The pillared products had surface areas of 200–260 m2/g and pore volumes of about 0.18 cm3/g. The uptake of Al by the clay and the micropore surface area of the pillared products were proportional to the fraction of smectite layers in the I/S. The thermal and hydrothermal stability of the pillared I/S was similar to that of pillared montmorillonite prepared using the same procedure.
K-Rich Mordenite from Late Miocene Rhyolitic Tuffs, Island of Samos, Greece
Authors: Pe-Piper G. , Tsolis-Katagas P.
Published: August 2006

Mordenite occurs in hydrothermally altered rhyolitic volcanic rocks at the margin of a Late Miocene lake basin on the island of Samos, Greece. The mordenite was identified by its X-ray powder diffraction pattern and appearance in scanning electron micrographs. Electron microprobe analyses show high Si, Ca, and K, low Na, and high balance errors. The b cell dimension is consistent with a high Si/(Al + Si) ratio, and the balance errors are apparently due to Na deficiency. The missing Na was estimated from the amount required to give (Si + Al) = 48 and yielded analyses comparable with X-ray fluorescence analyses of samples predominantly of mordenite. Even after this correction, the mordenite had a low Na:K ratio compared with most analyses reported in the literature. The peculiar chemistry of the mordenite may have resulted from a high-temperature metasomatic origin as a result of basaltic volcanism at the basin margin and characterized by hydrothermal circulation of alkaline lake water rich in K.
X-Ray Powder Diffraction Rietveld Characterization of Synthetic Aluminum-Substituted Goethite
Authors: Fazey P. G. , O'Connor B. H. , Hammond L. C.
Published: August 2006

Riet veld X-ray powder diffraction (XRD) analysis has been evaluated as a procedure for characterizing Al-substituted goethite according to the Rietveld scale factor, unit-cell parameters, and atom positional parameters. The study was conducted with three synthetic goethite samples for which the degree of Al substitution for Fe determined by chemical analysis was 8.0 ± 0.4, 12.0 ± 0.4, and 20.1 ± 0.4 mole %. The weight fractions of crystalline material (WFCM) in the specimens, determined from the Rietveld scale factors after correcting for adsorbed water and impurities, were 0.878 (esd = 0.014), 0.919 (0.014), and 0.965 (0.015), respectively. The Al mole % substitutions, inferred from the Rietveld cell parameters according to the method of Schulze (1984), were 10.4 ± 2.5, 16.5 ± 2.6, and 17.1 ± 2.6, respectively. The cause of the significant difference between the second value and the chemical analysis result is not known. The atom positional parameters did not differ significantly within the sample suite and agreed satisfactorily with literature values. The results have demonstrated the value of using Rietveld XRD analysis to determine simultaneously the WFCM and Al mole % substitutions, as well as to confirm the non-hydrogen atom positions.
Characteristics of Products from the Acid Ammonium Oxalate Treatment of Manganese Minerals
Authors: Mendelovici Efraím , Sagarzazu Amaya
Published: August 2006

To determine the parameters that control the attack of Mn minerals by acid ammonium oxalate in darkness (AAOD), rhodochrosite, pyrolusite, manganosite, hausmannite, and bixbyite were shaken with AAOD for 2 hr. These treatments were followed systematically by X-ray powder diffraction (XRD) and AAOD-extractable Mn analyses. About 5% of original hausmannite (surface area = 6 m2/g) remained in the solid residue of the AAOD treatment; however, if the hausmannite surface area was increased to 8 m2/g, by grinding, it completely dissolved in oxalate. Synthetic hausmannite of high surface area (37 m2/g) and rhodochrosite were completely dissolved by oxalate. Manganosite (1.5 m2/g) and especially pyrolusite (~ 1 m2/g) were more resistant to AAOD attack. Ground manganosite (4.2 m2/g) dissolved completely, but ground pyrolusite (7.2 m2/g) was only partially attacked by AAOD, inasmuch as about 25% of pyrolusite was found in the residue. An increase of the extraction time to 4 hr did not completely dissolve the ground pyrolusite.

As a result of the AAOD treatment, MnC2O4 · 3H2O and MnC2O4 · 2H2O precipitated from the oxalate solutions with all starting minerals, except pyrolusite (~ 1 m2/g), which only slightly dissolved. The seldom reported MnC2O4 · 3H2O phase was identified in residues of freshly extracted samples by its strong characteristic peak at 6.5.-6.6 Å, the intensity of which gradually decreased and disappeared over several days when the sample was exposed to ambient conditions (22°C and 70% relative humidity). The trihydrate phase also collapsed after heating AAOD-treated rhodochrosite at 50°C; α-MnC2O4 · 2H2O was identified as the main crystalline product. Heating the α-MnC2O4 · 2H2O product at 115°C overnight transformed most of it to MnC2O4. The color of the oxalate-treated samples ranged from pinkish-gray to black (7.5 YR); their surface area ranged from about 20 to 30 m2/g. The degree of transformation of Mn minerals by oxalate depended on the surface area and structural characteristics of the starting materials.
Burial Diagenesis in Two Montana Tertiary Basins
Authors: McCarty Douglas K. , Thompson Graham R.
Published: August 2006

Samples from initially smectite-rich Tertiary continental volcaniclastic sediment from the Deer Lodge and Big Hole basins of southwestern Montana show a general decrease in illite/smectite (I/S) expandability with increasing burial depth. The mineralogical trends in cuttings from seven wells are interrupted by discontinuities in which I/S expandability abruptly decreases by 30 to 80%. These discontinuities coincide with stratigraphic unconformities in four wells in which the stratigraphy is known. Core samples show a wide range of I/S expandabilities over short stratigraphic intervals, possibly due to composition, porosity, and permeability variations. Sericite coexists with I/S in the deep core samples. A core sample from 7958 ft (2425 m) contains an R3-ordered I/S having a nearly ideal 3:1 illite: smectite ratio, similar to the mineral tarasovite. The structure of this I/S is dominated by stacks of four 2:1-layer fundamental illite particles and small proportions of thicker particles randomly interstratified among the four-layer particles.
Discrimination of Kaolinite Varieties in Porters Creek and Wilcox Sediments of North-Central Mississippi
Authors: Reynolds William R.
Published: August 2006

Use of a discriminant analysis has verified and grouped three suspected varieties of kaolinite found in kaolin-rich clay strata of late Paleocene to early Eocene age across north-central Mississippi. Initial identification of each type of kaolinite was based on clay-texture characteristics observed on scanning electron micrographs and the differences in pattern configurations of X-ray diffractograms. The discriminant function used for data treatment clearly segregated and grouped each variety. The discrimination variables were found to be the Hinckley index and, to a lesser extent, the Si4+ content relative to the Al3+ content.

The oldest variety is the Blue Mountain clay, composed of preserved hexagonal plates usually clustered into booklets with a vermiform texture. The Ashland variety, stratigraphically younger than the Blue Mountain clay, appears to have been derived from the erosion of the Blue Mountain clay. The Ashland cannot be recognized by any type of diagnostic texture, as it is made up of individual plates that have been corroded and abraded to the point where a hexagonal outline can no longer be recognized. The Sardis variety is the stratigraphically youngest of the three varieties and is at least a second, or possibly a third generation detrital product. The Sardis clay can be recognized by a distinct “ribbon” or “swirl” texture commonly found in ball clays.

Data from this study are not sufficient for complete petrogenetic interpretation. However, speculation on possible differences in depositional environments and modes of deposition can be based on the data at hand. The Blue Mountain variety is considered from previous studies to be primary. The Ashland variety is probably a first generation alluvial clay. The Sardis variety appears to be a multiple generation, detrital product that accumulated as part of overbank swamp deposits.
Flocculation of Illite/Kaolinite and Illite/Montmorillonite Mixtures as Affected by Sodium Adsorption Ratio and pH
Authors: Goldberg Sabine , Forster Harold S. , Heick Elizabeth L.
Published: August 2006

The effect of electrolyte concentration, exchangeable sodium percentage (ESP), sodium adsorption ratio (SAR), and pH on the flocculation-dispersion behavior of 50/50 mixtures of reference illite with reference kaolinite or reference montmorillonite was investigated. The clays were Na- or Ca-saturated and freeze-dried before use. Critical coagulation concentrations (CCCs) were investigated in the range of pH 5.9 to 9.6, percent Na-clay 0, 10, 20, 40, 60, 80, and 100 and SAR 0, 10, 20, 40, 60, 80, and ∞. CCC values increased with increasing ESP, increasing SAR, and increasing pH. The pH dependence of illite/kaolinite was greater than that of illite/montmorillonite especially at high ESP and SAR. The presence of illite did not play a dominant role in determining flocculation-dispersion behavior of the 50/50 clay mixtures. The CCCs of illite/kaolinite resembled reference illite more than reference kaolinite for SAR 0 to SAR 60. Illite/montmorillonite exhibited CCCs more similar to reference illite than reference montmorillonite at SAR 40 and SAR 60. At the agriculturally desirable ESP and SAR values of 0 to 15, all the 2:1 clays and 2:1 clay mixtures demonstrated similar CCC values.
Detection of Tetrahedral Fe3+ Sites in Nontronite and Vermiculite by Mössbauer Spectroscopy
Authors: Luca Vittorio
Published: August 2006

Mössbauer spectra were obtained for five Ca-exchanged nontronites and one Ca-exchanged vermiculite as the 2-layer hydrates following dehydration at 200°C. Exchange of the samples with Ca2+ and subsequent dehydration resulted in the appearance of a shoulder at about −0.50 mm/s in the Mössbauer spectra of some of the samples. The appearance of these shoulders necessitated the inclusion of doublets with Mössbauer parameters corresponding to tetrahedrally-coordinated Fe3+ (IVFe3+) in the model used to fit the Mössbauer spectra. That the IVFe3+ sites detected in these samples were those in the nontronite structure was confirmed using samples whose IVFe3+ contents have been previously determined from chemical analysis. It appears that this sample preparation method allowed IVFe3+ contents to be determined to within 40%. On this basis, the IVFe3+ content appeared to be unrelated to the total Fe content for the samples studied.
Structure-Composition Relationships in Trioctahedral Chlorites: A Vibrational Spectroscopy Study
Authors: Prieto A. C. , Dubessy J. , Cathelineau M.
Published: August 2006

Raman and Fourier-transformed infrared spectra of natural trioctahedral chlorites of polytype IIb were obtained for a series of samples characterized by distinct Fe/(Fe + Mg) and Si/Al ratios ranging, respectively, from 0.04 to 0.94 and from 5.18 to 1.86. All samples were characterized by X-ray powder diffraction, and quantitative electron microprobe analysis. In the 3683-3610-cm−1 spectral range, the wave number of the OH-stretching band from the 2:1 layer (band I) decreased with an increase of iron content at constant Al(IV) content. The more intense bands II and III at about 3600 cm−1 and 3500 cm−1, were assigned to hydroxyl groups involved in hydrogen bonds: (SiSi)O... HO, with the hydrogen bonds being roughly perpendicular to the basal plane, and (SiAl)O... HO, respectively. At higher tetrahedral Al and octahedral Fe contents, spectra exhibited OH-bands II and III, respectively, at a lower frequency. Band III intensity increased and band II was enlarged for chlorites displaying higher Al(IV) contents.

In the 1300–1350-cm−1 spectral range, most infrared spectra displayed intense bands at 1090, 1050, 990, and 960 cm−1, which were assigned to T-O stretching of symmetry species Al and E1. The second type of bands observed both in Raman and infrared spectra were at about 650–800 cm−1; they were assigned to OH vibrations and were strongly dependent on the composition of the interlayer octahedral sheet, especially on the Fe content.
Use of Methylene Blue and Crystal Violet for Determination of Exchangeable Cations in Montmorillonite
Authors: Rytwo G. , Serban C. , Nir S. , Margulies L.
Published: August 2006

A procedure for the determination of cation exchange capacity (CEC) and the amounts of exchangeable cations adsorbed to montmorillonite is proposed. The method consists of a single incubation of the clay in a suspension containing a low concentration of an organic dye of large binding affinity, followed by analysis of the displaced inorganic cations by inductively-coupled plasma emission spectrometry (ICPES). The CEC is obtained by taking the largest sum of displaced exchangeable cations. Montmorillonite suspensions were incubated with methylene blue (MB) or crystal violet (CV) at dye concentrations below 4 mM, for one, three or fourteen days. For total dye concentrations up to the CEC, all the dye was adsorbed and equivalent amounts of exchangeable cations were released. Both dyes could adsorb to the clay in excess of the CEC.

After one day of incubation in the presence of dye concentrations of about 50% in excess of the CEC, the total amounts of cations released were reduced to below the CEC. This reduction was interpreted as due to massive aggregation of the clay particles induced by the dye. With CV the total amounts of cations released after three or fourteen days of incubation increased and became equal to the CEC.

The same CEC was found for Na-, Ca- and SWy1 crude-montmorillonite, by employing either of the dyes.
Weathering of a Chromian Muscovite to Kaolinite
Authors: Singh Balbir , Gilkes R. J.
Published: August 2006

Single crystal X-ray diffraction and electron-optical analysis were used to investigate the weathering of a chromium-bearing muscovite (fuchsite). The muscovite had mostly altered to kaolinite with minor amounts of halloysite occurring between kaolinite plates. Evidence for both epitactic and topotactic growth of kaolinite from muscovite was obtained and no intermediate poorly-crystalline phases were detected. About half of the Cr in fuchsite was incorporated into kaolinite, whereas most of the Ti, Fe and Mg was lost.
X-Ray Diffraction Patterns of Montmorillonite Oriented Films Exchanged with Enantiomeric and Racemic Tris(2,2′-Bipyridyl)Ruthenium(II)
Authors: Villemure Gilles
Published: August 2006

X-ray diffraction patterns of oriented films of montmorillonite containing enantiomeric tris(2,2′-bipyridyl) ruthenium(II) chloride (Ru(bpy)22+) show a peak corresponding to basal spacings of approximately 27 Å. This peak is absent from the X-ray patterns of montmorillonite films containing racemic cations. A basal spacing of 27 Å is consistent with the adsorption of 2 layers of the enantiomeric cations in each interlayer space. Under the same condition only one layer of the racemic cation was intercalated (basal spacings of 17.9 Å). These results are in accord with previous reports that montmorillonite can adsorb more of the optical isomers than of the racemic mixture of Ru(bpy)32+. Addition of NaCl to the mixtures resulted in an increase in the level of adsorption of the racemic cations and in the appearance of a peak at 27 Å in the X-ray pattern.
Clay Mineralogy, Alteration History, and Economic Geology of the Whitemud Formation, Southern Saskatchewan, Canada
Authors: Pruett Robert J. , Murray Haydn H.
Published: August 2006

The Upper Cretaceous (Maastrichtian) Whitemud Formation is a potentially commercial kaolin deposit located in southern Saskatchewan and southeastern Alberta. The Whitemud Formation contains a lower kaolinitic sandstone, a middle lignite and carbonaceous shale, and an upper interbedded siltstone and claystone. The sediments that comprise the rocks of the Whitemud Formation were deposited on alluvial or upper deltaic plains located along the northwest flank of the Williston Basin.

Mineralogy and textures were determined by X-ray powder diffraction, scanning electron microscopy, and optical microscopy. Kaolinite abundance increases upward from the underlying rocks of the Eastend Formation through the Whitemud Formation, and the abundance of smectite, micas, and feldspars decreases from the Eastend Formation into the Whitemud Formation. Vermiform kaolinite crystals are in close spatial association with feldspar and mica grains. Near the top of the Whitemud Formation, etched quartz and feldspar grains, and gibbsite suggest the presence of a strong chemical leaching environment.

Mineral distributions, presence of root remains, pedologic mottles, grain coatings composed of clay, and soil horizons indicate the Whitemud Formation sediments were modified by intense weathering in a paleosol environment.

Kaolin concentrated from selected kaolinitic sandstone deposits, and beneficiated by oxidation, leaching, and high-intensity wet-magnetic separation has a product brightness up to filler quality. Recovery of lowabrasion kaolin is low and viscosity of a fine-particle kaolin fraction is high. Economics of producing a wet-processed filler-grade kaolin is marginal.
Mineralogy and Genesis of Clays in Postmagmatic Alteration Zones, Makurazaki Volcanic Area, Kagoshima Prefecture, Japan
Authors: Kawano Motoharu , Tomita Katsutoshi
Published: August 2006

Two distinct zonal sequences of clay minerals (H- and L-type) were found around silicified rocks in the Makurazaki volcanic area, Kagoshima Prefecture, Japan. The clay mineral sequences from the inner to the outer parts of the alteration aureoles are: 1. H-type, pyrophyllite → dickite → 2M2 mica → sudoite → tosudite; and 2. L-type, kaolinite → rectorite → smectite. The structural formula for the sudoite is: (Al1.04Mg1.28Fe3+0.20Ti0.03Li0.01K0.02Na0.01(OH)6Al2.00(Si3.54Al0.46)O10(OH)2. It is characterized by relatively large amounts of Mg and very small amounts of Li. The polytype is identified as IIb. The chemical analysis of tosudite shows that the sample is composed of an interstratification of sudoite-like and beidellite-like layers. The structural formula for rectorite is: (K0.45Na0.19Ca0.01Mg0.01)(Al1.81Fe3+0.04Mg0.13Ti0.03)(Si3.41Al0.59)O10(OH)2, suggesting that the nonexpandable and expandable layers have K-mica-like and beidellite-like compositions, respectively. These clay minerals in the H- and L-type alteration aureoles were formed under relatively high- and low-temperature conditions, respectively, with pH value and K- and Mg-activities increasing as the fluids ascended through the wall rocks.
Hydrolysis of Azinphosmethyl Induced by the Surface of Smectites
Authors: Sánchez-Camazano M. , Sánchez-Martín M. J.
Published: August 2006

The effect of layer charge and of the interlayer cations of smectites on the hydrolysis of azinphosmethyl (0,0-dimethyl S-((4-oxo-l,2,3-benzotriazine-3(4H)-yl)methyl) phosphorodithioate) in an aqueous medium was investigated. Ultraviolet spectroscopy was used for monitoring the hydrolysis process. Hydrolysis of the pesticide is catalyzed by Ca-hectorite (layer charge 0.216) but is not catalyzed by Ca-nontronite nor by Ca-montmorillonites with a layer charge above 0.216. The Mg- and Cu-hectorites and Cu-montmorillonite with a layer charge of 0.264 also show catalytic activity. The catalytic activities of the Ca2+ and Cu2+ cations as exchange cations of the smectite and as salts are compared. In agreement with previously reported work, the results show that the hydrolysis of azinphosmethyl may involve the adsorption of the pesticide into the interlayer space of the smectites, forming a bidentate complex with the interlayer cations. This interaction must enhance the electrophilic nature of the phosphorus atom, thereby facilitating its nucleophilic attack by the OH-ion and producing rupture of the P-S bond.
Effects of Freezing on Colloidal Halloysite: Implications for Temperate Soils
Authors: Blank Robert R. , Fosberg Maynard A.
Published: August 2006

The literature reports that freezing of aqueous aluminosilicate clay suspensions can produce clay aggregates that disperse with agitation. Our experiments indicate that colloidal suspensions extracted from north Idaho loess soils (Boralfs), when frozen, form silt- and sand-sized agglomerates that resist dispersion with agitation. XRD and TEM analyses showed that colloids are dominantly halloysite between 0.10 to 0.30 μm in diameter. The colloidal halloysite has anomalously high mole ratios of Si/Al and a high Fe content. Freeze-produced agglomerates are light yellow to yellowish-brown in color, occur in the form of plates, wedges, cuspates, or laths, and often exhibit uniform optical properties, suggesting a crystalline product. Selected area electron diffraction, however, indicates that the agglomerates are polycrystalline. With proper orientation, agglomerates produce acute bisectrix interference figures that are optically negative with variable 2V, generally <30°. XRD analyses and IR spectra imply that the agglomerates are halloysite. Measured optical properties, however, are difFerent than those reported for halloysite and may be affected by the high Fe content and polycrystalline nature of the agglomerates. Grains, exhibiting similar optical properties as laboratory-produced agglomerates, are a minor proportion of the very-fine sand fraction in some horizons of the soils studied. Freeze-aided agglomeration of colloidal material may be an important process in temperate climates. It may be overlooked because of particle destruction by soil pretreatments or morphological order and/or optical similarity to some micaceous minerals.
Influence of Climate on the Iron Oxide Mineralogy of Terra Rossa
Authors: Boero Valter , Premoli Alessandra , Melis Pietro , Barberis Elisabetta , Arduino Enza
Published: August 2006

Terra rossa samples were taken from the B horizons of soil profiles and from cracks within limestone in Italy. The average annual temperature (AAT) of the sites ranged from 8.4 to 20.3°C and the average annual precipitation (AAP) from 511 to 3113 mm, with either a 5–6 month water deficit or a large water surplus. Goethite and hematite were identified in all the samples. Under a moist (> 1700 mm AAP) and cool (13°C AAT) climate, a xeric, hematitic pedoenvironment was preserved by the well-litified carbonate rock. Hematite occurred in trace amounts, even with an AAT of 8.4°C and an AAP of 3300 mm, confirming the specific role of the hard limestone on the pedoclimate of terra rossa. The lowest mean crystallite dimension of goethite and hematite was found in the samples from the wettest sites, and in these samples hematite was nearly free of Al substitution. Rubification in terra rossa appeared to be due to the specific pedoenvironment. The hematite cannot be considered a relict phase formed under another climate. Illite and kaolinite were the main clay minerals in samples from xeric sites whereas more weathered clays, such as Al-interlayered vermiculite, occurred in cool, moist sites. We postulate that the processes of rubification and vermiculitization could have taken place at the same time.