The highest frequency near-infrared (NIR) combination bands for specimens of four species of mica—montmorillonite-beidellite, illite, chlorite, and kaolinite—were correlated with respect to Al2O3 content. A direct linear correlation was found between the combination band positions and the Al2O3 contents of the montmorillonite-beidellite series, which may be given as: ν̄ cm−1 = (5.38 ± 0.04) (% Al2O3) + (4412.8 ± 0.9). A similar linear correlation for muscovite is: ν̄ cm−1 = (6.10 ± 0.25) (% Al2O3) + (4434.1 ± 8.3).

Possible NIR band interferences are shown for different mineral mixtures, along with the correlation of different illites with muscovite. No combination bands were found in the frequency region 4425 cm−1 to 4625 cm−1 for specimens in which the Al2O3 content was only in the tetrahedral layer sites.

Kaolinite was converted into illitic clays in a 2.58 m KOH solution in gold capsules using cold-seal pressure vessels at 225°, 250°, 300°, and 350°C and 500 bars. The XRD shows that the major reaction products are illitic clays with no interlayer expandability. The TEM shows that the illitic clays appear mainly platelet-like with a K/Si ratio close to that of muscovite/illite. The extent of the conversion was monitored by measuring the XRD peak ratio of muscovite (illite) and kaolinite in quenched run products. The results reveal that kaolinite converts to muscovite/illite in the KOH solution at an initial rate two to three orders of magnitude faster than that of similar reactions at near-neutral conditions.

Smectite and zeolites were formed from a volcanic glass as the products of reaction with NaOH solution at 90°C and 100°C under atmospheric pressure. Formation conditions of smectite and various zeolites were determined by the ratio of the amounts of volcanic glass (g) to NaOH (g) in the solution. Smectite was formed under the condition that the values of weight of volcanic glass (g)/(NaOH(g)/40) are between 0.5 and 6. Fe was an important constituent of the octahedral layer of smectite.

A combined application of electron paramagnetic resonance (EPR) and Fourier-transform infrared (FTIR) spectroscopies with thermal methods was used to determine the chemical form of V(IV) in a Georgia kaolinite (KGa-I). Precise values of the EPR spectroscopic g-values and hyperfine coupling constants were obtained for an untreated sample (g∥ = 1.940, A∦ = 18.71 mT; g⊥ = 1.966, A⊥ = 7.63 mT). Heating the sample to 1000°C in steps while monitoring phase changes with EPR and FTIR spectra led to the following structural interpretations: 1) Vanadium (IV) occurs almost entirely as an isomorphically substituted species in the octahedral sheet of KGa-1 kaolinite; 2) during the dehydroxylation of kaolinite at about 500°C and the subsequent formation of metakaolinite, V(IV)-substituted octahedral sites are readily converted into truncated octahedra exhibiting fourfold coordination; and 3) in these highly distorted four-coordinated sites, V(IV) is metastable, being completely oxidized at about 800°C.

This study assesses the distribution of Al and Fe in mixed-layer illite/smectites (I/S) in shales undergoing burial diagenetic changes, using evidence from 27Al NMR, XRD, and chemical analyses. Samples studied include a sequence of mixed-layer I/S (ranging from 40% to 68% illite layers) in shales from a well located in the Caillou Island Oil Field, Terrebonne Parish, Louisiana, as well as synthetic mica-montmorillonite (Syn-1), Silver Hill illite (IMt-1), K-benonite (ISMt-1), an Fe-bearing muscovite, phengitic muscovite, and a randomly interstratified mixed-layer I/S with 50% illite layers. Using a simplified model, where Fe3+ isomorphously substitutes randomly for [6]Al in the dioctahedral 2:1 structure, the 27Al NMR signal intensities are examined with regard to the paramagnetic deshielding effect of the Fe3+. The rapid decrease in paramagnetic deshielding with distance allows for a spherical “wipeout” model with a radius of 6 Å, over which there is complete effective paramagnetic line broadening (i.e., Al within the sphere is not “seen”). Using the average dimensions of a dioctahedral mica, the expected relative intensities of the octahedral and tetrahedral Al signal are determined as a function of Fe2O3 content.

Observed 27Al signals, normalized per unit weight of Al2O3 and relative to the lowest Fe-bearing phase, show a clear trend of decreasing intensity with increasing Fe2O3 content. Normative fitting of oxide data to structural formulae reveals a similar trend of decreasing 27Al intensity with increasing fraction of dioctahedral site occupied by Fe3+. Agreement between the observed 27Al intensities of low Fe-bearing 2:1 phyllosilicates and 27Al intensities predicted using the wipeout model indicate regular ordering of Fe and Al within the low Fe-bearing phases. However, observed 27Al intensities for the I/S specimens fall into a region where the amount of Al seen is in excess for the given XFe, thus indicating segregation of Al and Fe domains.

The second order quadrupole effect for the [6]Al site in the I/S fraction of shales decreases very slightly with increasing depth and percent of illite in the I/S, but not enough to effect site quantitation. Quantitative apportionment of elements into the I/S phase of the <0.2 µm fraction using NMR constraints shows directly a trend of increasing number of [4]Al sites and no change in the number of [6]Al sites with increasing degree of illitization for samples from the Gulf Coast diagenetic environment. Stoichiometry indicates an approximate 1:1 substitution of tetrahedral Al for Si over the 40–68% range of illite in I/S examined.

The effect of three organic ligands on the adsorption of Cu on Ca-montmorillonite was studied. The results indicate that these effects include three different processes:

1. 1) Enhanced uptake of positively charged Cu-ligand complexes by ion-exchange.

2. 2) Formation of ternary surface complexes involving surface aluminol groups.

3. 3) Inhibited uptake due to competition between the surface ligands and the dissolved ligands for dissolved copper.

Ethylenediamine promotes Cu uptake by ion-exchange at low pH but tends to suppress adsorption at aluminol groups by ligand competition at high pH. The same mechanisms are operative for β-alanine; however, the uptake of Cu(β-ala)+ by ion-exchange is not promoted by the attached ligand. The influence of malonate includes both ligand competition and formation of ternary complexes. A quantitative interpretation based on the surface complexation model using the least-square programs FITEQL (Westall, 1982) and GRFIT (Ludwig, 1992) is presented. The obtained equilibrium constants are listed in Tables 2b and 3.

Highly tectonized contact between serpentinite and younger pegmatite in the magnesite mine of Wiry contains various layer silicates. Vermiculite, chlorite, smectite, and interstratified mica-vermiculite were recognized by means of routine XRD examination. Two three component interstratifications of mica-vermiculite-chlorite and chlorite-swelling chlorite-smectite were identified by a combined procedure of deconvolution of the XRD patterns and simulation of XRD tracings. A mineral with large diffraction maxima, displaying “chlorite intergrade” characteristics, appeared to be a mixture of chlorite, mixed layer chlorite-smectite, and vermiculite. Polytypes of phyllosilicates were determined by the X-ray transmission method. Due to the heritage of parent mineral polytype structure by transitional products of alteration, two distinct sequences of layer silicates were observed: one formed from trioctahedral mica (vermiculite, mixed layer mica-vermiculite); and one evolved from chlorite (e.g., mixed layer chlorite-swelling chloritesmectite). A tentative scheme of the primary contact zone structure, not obscured by subsequent brittle tectonics either by transformation of layer silicates, is proposed.

Hydroxy-chromium solutions were prepared from chromium nitrate solutions by adding NaOH with OH/Cr = 2.

The solutions were treated at 20°C and 60°C. The hydrolysis times were from 1 to 100 days. Polymeric species in hydrolyzed chromium solutions were followed by visible absorption spectra within the range 325–800 nm and by pH measurement. OH-Cr-smectite with high d(001) spacing (2.07 nm) was obtained when hydroxy-chromium solution was prepared at 60°C and with 1-day hydrolysis. When this sample was heated up to 350°C the basal spacing collapsed at 1.8 nm.

The samples were characterized by X-ray diffraction and N2 adsorption-desorption isotherms.

Bulk and size-fractionated kaolinites from seven localities in Australia as well as the Clay Minerals Society Source Clays Georgia KGa-1 and KGa-2 have been studied by X-ray diffraction (XRD), laser scattering, and electron microscopy in order to understand the variation of particle characteristics across a range of environments and to correlate specific particle characteristics with intercalation behavior. All kaolinites have been intercalated with N-methyl (NMF) after pretreatment with hydrazine hydrate, and the relative efficiency of intercalation has been determined using XRD. Intercalate yields of kaolinite: NMF are consistently low for bulk samples that have a high proportion of small-sized particles (i.e., <0.5 µm) and for biphased kaolinites with a high percentage (>60%) of low-defect phase. In general, particle size appears to be a more significant controlling factor than defect distribution in determining the relative yield of kaolinite: NMF intercalate.

An aluminous Ca-montmorillonite from southern Manitoba, Canada, has been shown to generate very low pH values in clay/groundwater slurries over a range of ionic strength of the groundwater (fresh and saline) and temperatures from 25°–90°C. Dialysis experiments as well as results of X-ray diffraction and FTIR vibration spectroscopy point to an acidification mechanism that involves hydrolysis of exchangeable Al3+ ions, thus releasing protons, and the subsequent intercalation of gibbsite-like hydroxy-Al complexes into the smectite lattice forming a non-expandable “Al”-montmorillonite.

A glass in the intermediate composition of montmorillonite and beidellite, 50/50 in mole ratio, was treated under a hydrothermal pressure of 100 MPa, in the temperature range from 250 to 500°C and durations from 2 to 129 days. The phases identified in the products were plotted in a time-temperature-transformation (TTT) diagram. The TTT diagram showed that the regularly interstratified montmorillonite-beidellite (r.i.M-B) was a metastable phase above the temperature of 350°C and changed to the assemblage of Na-rectorite + saponite + quartz, through the intermediate assemblage of beidellite + saponite + quartz. The TTT diagram suggested also that the r.i.M-B might be a stable clay mineral below the temperature of 300°C in the middle region of montmorillonite-beidellite pseudo-binary system, although the laboratory confirmation of the mineral stability was not easy for the sluggish reaction.

Hydrotalcite-like compounds (HT) with 24%–48% Al3+-substitution have been synthesized in the Mg2+-Al3+-Fe(CN)64- system. Conditioning of the synthesized and air-dried compound with K4Fe(CN)64- solution at 80°C was essential to obtain the 80%–90% pure ionic Fe(CN)64- form on an equivalent basis. A linear decrease in ao with an increase in the mole ratio of R = Al3+/(Mg2+ + Al3+) was extended to R = 0.48. The formation of highly Al3+-substituted HTs has been corroborated by the decrease in the hexagonal lattice constant ao down to 3.016 Å. The ao value was independent of the interlayer anions. The CO2 adsorption profiles were dependent upon both the Al3+-substitution and the interlayer distance. The isosteric heat of CO2 adsorption was 43.3 kJ mol-1 in the range of adsorption of 20 to 40 cm3 g-1 at 298 K and 0.1 MPa.

The crystal structure of Keokuk kaolinite, including all H atoms, was refined in space group C1 using low-temperature (1.5 K) neutron powder diffraction data (λ = 1.9102 Å) and Rietveld refinement/difference-Fourier methods to Rwp = 1.78%, reduced χ2 = 3.32. Unit-cell parameters are: a = 5.1535(3) Å, b = 8.9419(5) Å, c = 7.3906(4) Å, α = 91.926(2)°, β = 105.046(2)°, γ = 89.797(2)°, and V = 328.70(5) Å3. Unit-cell parameters show that most of the thermal contraction occurred along the [001] direction, apparently due to a decrease in the interlayer distance. The non-H structure is very similar to published C1 structures, considering the low temperature of data collection, but the H atom positions are distinct. The inner OH group is essentially in the plane of the layers, and the inner-surface OH groups make angles of 60°–73° with the (001) plane. Difference-Fourier maps show minor anisotropy of the inner-OH group in the [001] direction, but the inner-surface OH groups appear to have their largest vibrational (or positional disorder) component parallel to the layers. Although no data indicate a split position of any of the H sites in kaolinite, there is support for limited random positional disorder of the H atoms. However, these data provided no support for a space group symmetry lower than C1.

Clay mineralogy (including illite crystallinity) was studied in Pennsylvanian synorogenic sediments (Atoka Formation) in the subsurface of the Arkoma Basin and the adjacent Ouachita thrust belt. Vitrinite reflectance values range from ≥0.8% at the surface up to as high as 4.7% Ro at the base of the Atoka Formation. The mineralogy of the <2 µm fraction of the mudrocks is fairly monotonous and composed of illite (<10% interstratified smectite), Fe-chlorite, kaolinite, quartz, and traces of feldspars. Kaolinite is common at shallow levels and “disappears” in most wells at a thermal maturity of 1.9–2.1% Ro, suggesting its possible use as an independent paleothermal indicator in this basin. Illite crystallinity (IC) values are fairly high (0.3–0.5° 2θ) and show little variation throughout the entire maturity range. In addition, no relation was observed between vitrinite reflectance and illite crystallinity, indicating that IC is not a useful paleothermal indicator in these rocks. Illite is almost exclusively of the 2M1 polytype, suggesting a predominantly detrital origin. Incipient metamorphic and low-grade metamorphic mudrocks in the Ouachita thrust belt to the east of the Arkoma Basin are regarded as the source rocks for the clays of the Atoka Formation. Rapid transportation and deposition by turbidity currents probably played a key role in protecting these unweathered micas from pervasive alteration in the terrestrial environment.