Some minerals which have been referred to as corrensite are considered together with some related minerals. It is suggested that the name corrensite be retained for the original material so described—namely, a I:1 regular interstratification of chlorite and swelling chlorite. The possible constitution of swelling chlorite, its difference from vermiculite, and its relationship to labile chlorites produced synthetically are all discussed.

In the Miller Field, diagenetic quartz abundance, isotopic compositions and salinities of quartz-cementing fluids display a distinct pattern which is related to the structural depth of the reservoir sandstones. Quartz cement volumes increase from the crest of the field (average 6.0±1.5%) towards the flanks of the field (average 13.2±2.1%) and directly reduce reservoir porosity. By integrating petrographic observations with results of fluid inclusion measurements and O isotope analyses of diagenetic quartz, the pattern of quartz cementation is seen to be related to the reservoir filling history. Oil filled the crest of the reservoir first and prevented extensive quartz cementation. At greater depth in the reservoir oil zone, quartz overgrowths continued to precipitate until inhibited by the developing oil column. Oxygen isotope compositions of diagenetic quartz imply that quartz cement continued to precipitate in the water zone of the reservoir up to the present day.

The low-charge dioctahedral 2:1 phyllosilicates are an important group of clay minerals that have a low degree of cation substitution and very weak interlayer interatomic interactions which are difficult to reproduce with quantum mechanical calculations. In order to study the crystallographic properties of these compounds with density functional theory (DFT) quantum-mechanical methods, an optimization of norm-conserving pseudopotentials of Al, Si, O, H and Na atoms has been carried out, and an optimization of the cutoff radii of the basis sets has been accomplished. Crystallographic properties and vibrational stretching frequencies of the OH groups, ν(OH), have been calculated, being consistent with previous computational and experimental results. All frequencies can be related to the different molecular environment of the OH groups. The effect of octahedral Fe3+ substitution on the ν(OH) frequency is reproduced. Several configurations of cation substitutions and interlayer cation (IC) positions are studied in low-charge dioctahedral 2:1 phyllosilicates, such as Al4(Si7–xAlx)O20(OH)4Nax, with x = 0.25, 0.50 and 0.75, indicating that the IVAl3+ is highly dispersed and the IC tends to be in the substituted ditrigonal hole. For the Al4(Si7Al)O20(OH)4Na composition, the trans-vacant form is more stable than the cis-vacant one.

Vivianite [Fe3(PO4)2·8H2O] is easily oxidized in the presence of air. In this work, we studied the oxidation and incongruent dissolution of vivianite in a calcareous medium containing an anion-exchange resin (AER) that acted as a sink for phosphate. Freshly prepared vivianite suspensions with calcite sand and an AER membrane were oxidized and stirred by bubbling air or CO2-free O2. Experiments were finished when oxidation rate and P removal by the AER became slow, which was at 53 days (air system) or 28 days (CO2free O2 system). At these times, the respective values of the Fe(II)/total Fe ratio were 0.29 and 0.12, and the respective values of the atomic P/Fe ratio were 0.15 and 0.11. The final product of the oxidation was poorly crystalline lepidocrocite in the form of thin (1 ­ 5 nm), irregular lamellae that were soluble in acid oxalate. The unit-cell edge lengths of this lepidocrocite were a= 0.3117, b= 1.2572, and c= 0.3870, vs. a= 0.3071, b= 1.2520 and c= 0.3873 nm for the reference lepidocrocite. The lepidocrocite lamellae contained occluded P (P/Fe atomic ratio = 0.03 ­ 0.04). The results of this and a previous study made us hypothesize that this occluded P is structural and occupies tetrahedral sites adjacent to the empty octahedral sites in the sheets extending on ﹛010﹜.

A study of the weathering of micaceous clays in some Norwegian podzols, includes semiquantitative estimates of minerals in the concentrated clay fractions which show a decrease in the amounts of illite and chlorite, and an increase in vermiculite and mixed-layer minerals upward in the profile. Illite, the dominant mineral at depth, weathers to hydrobiotite in the surface horizon of the profile. Subsequent weathering of hydrobiotite in this portion of the profile produces trioctahedral vermiculite and smectite, or intergrade smectite-chlorite.

Aniline, adsorbed from aqueous solution in 1% (w/v) clay suspensions, forms coloured complexes and polymerizes on Fe(III)- and Cu(II)-montmorillonite. As evidenced by the adsorption isotherms, and the coloration and spectroscopic (IR, ESR) characteristics of the organo-clay associations formed, the conditions under which these reactions take place and the mechanisms involved differ according to the exchange cation. Fe(III) interacts with the π electrons of the aromatic ring to give rise to radical cations or so-called type II complexes, provided the aniline concentration does not exceed 500 p.p.m. With Cu(II). an aniline concentration above 500 p.p.m. is required and the reaction occurs at the amine group, proceeding through coordination followed by free-radical formation.

This sub-committee consisting of Mr G. Brown (Chairman), Dr M. H. Hey, Dr D. M. C. MacEwan and Dr R. C. Mackenzie was asked to make proposals for the nomenclature of clay minerals and these proposals were presented in part at a C.I.P.E.A. meeting in Paris in July, 1954, where some useful discussion ensued. The outcome of that meeting was a suggestion that the proposals be published more fully. It is important to remember that these are proposals for consideration and not a set of rules. The Clay Minerals Group would welcome comments on these proposals (adverse or otherwise) or the comments may equally well be sent to C.I.P.E.A.

A bentonite sample from the Petreş ti deposit, Cluj County (Romania), was used to remove heavy-metal ions (Cd2+, Pb2+, Cr3+) from wastewaters. A representative sample of bentonite (P) was characterized using the Brunauer-Emmett-Teller (BET) method, wet chemical analyses, X-ray diffraction (XRD) and Fourier-transform infrared (FTIR) spectroscopy. The bentonite deposit from Petreş ti is present at the contact between Upper Jurassic limestones and basaltic andesites with subordinate basalt bodies. These rocks are composed of clay minerals (mainly smectite), with opal, quartz, feldspar and mica/illite as minor phases. The bentonite sample was used in powdered form (d < 0.2 mm) without any chemical treatment. The influence of the working regime, static and dynamic, on the process efficiency was studied using monocomponent synthetic wastewaters containing Cd, Pb and Cr ions. The bentonite sample proved to be efficient for the removal of these heavy-metal ions; removal efficiencies up to 100% (lead removal) were achieved.

Chemical and mineralogical transformations of phyllosilicates are among the most important in diagenetic environments in all types of rocks because they can exert a large control on the processes taking place in such environments and/or provide constraints for the conditions in which phyllosilicate transformation occurred. Dissolution-precipitation and solid-state transformation are usually the two mechanisms proposed for such reactions depending on the crystal-chemical and morphological similarities between parent and neoformed phases together with knowledge of the environmental conditions. These two mechanisms, however, may be at both ends of the spectrum of those operating and many transformations may take place through a mixture of the two mechanisms, generating observable elements that are characteristic of one or the other. In the present literature, the boundaries between the two mechanisms are not clear, mainly because dissolution-precipitation is sometimes defined at nearly atomic scale. It is proposed here that such small-scale processes are considered as a solid-state transformation, and that dissolution-precipitation requires dissolution of entire mineral particles and their dissolved species to pass into the bulk of the solution. Understanding the reaction mechanisms of diagenetic transformations is an important issue because they impinge on geochemical conditions and variables such as cation mobility, rock volume, fabric changes, rock permeability, stable isotope signature and phyllosilicate crystal-chemistry.

I propose that, in the lower range temperatures at which clay mineral transformations take place, energy considerations favour solid-state transformation, or reactions that involve the breaking of a limited number of bonds, over dissolution of entire grains and precipitation of crystals of the new phase. Large morphological changes are frequently invoked as evidence for a dissolution-precipitation mechanism but changes in particle shape and size may be achieved by particle rupture, particle welding or by hybrid processes in which dissolution-precipitation plays a minor role.

Past and recent studies of phyllosilicate transformations show chemical and structural intermediates indicating a large crystal-chemical versatility, greater than is commonly recognized. These intermediates include tetrahedral sheets of different composition within TOT units (termed polar layers), dioctahedral and trioctahedral domains in the same layer, and 2:1 and 1:1 domains also within the same layers. The existence of such intermediate structures suggests that the reaction mechanisms that generated them are within the realm of the solid-state transformation processes.

Some uses of clay-supported reagents in fine organic synthesis are discussed, in particular the catalysis of the phase-transfer preparation of formaldehyde acetals by quaternary ammonium montmorillonites. The preparation and some applications of clay-supported ferric nitrate, a new reagent which oxidizes alcohols into carbonyl derivatives, couples thiols into disulphides, nitrates phenols, and oxidatively couples pyrrole and benzaldehyde into tetra-phenylporphyrin, are also described

In many areas of geotechnical engineering it is necessary to have an estimate of the cation exchange capacity (CEC) of a soil in order to allow preliminary design estimates. Standard methods of CEC determination are time-consuming and involve several steps (e.g. displacement of the saturating cation requires several washings with alcohol). Therefore, a rapid method of CEC estimation would be very useful. During preliminary site investigations, the soil engineering parameters can be estimated from the considerable number of correlations available in the literature. In this study, relationships between CEC and various other soil engineering properties have been investigated, resulting in a quick method for estimating CEC.

Simple correlations were developed between CEC and specific surface area (SSA), soil organic matter (OM), clay fraction (CF), activity (A), Atterberg limits (liquid (LL), plastic (PL), and shrinkage (SL)), and modified free swell index (MFSI) of the soils. Strong correlations are observed between the CEC values and those for ethylene glycol monoethyl ether (EGME) uptake and methylene blue (MB) titration. However, no significant correlation was found between CEC and N2_SSA. No unique relationship was seen between CEC and CF (r2 <0.5). No relationship was observed between CEC and OM in this study. The best correlation coefficient between the CEC and Atterberg limits exists between CEC and LL (r2 = 0.61). No significant relationship was seen between CEC and PL or SL. The correlation coefficient between CEC and MFSI was 0.65. Multiple linear regression analyses were developed to investigate the contributions of different soil parameters to CEC. These analyses show that EGME_SSA, in combination with LL, accounted for 91% of the variation in CEC. Correlations between CEC and EGME_SSA, MB_SSA and LL appear to be sufficiently good to enable an indication of CEC to be estimated from these parameters.

Residual clays that developed on Permian and Carboniferous glass-rich silicic volcanic rocks (pitchstones, ignimbrites) at the Seilitz and Kemmlitz kaolin deposits, Saxony, Eastern Germany, contain locally abundant lath-shaped illite-rich illite-smectite mixed-layer minerals (I-S). Analyses by XRD and TEM-AES reveal a large illite percentage (>∼90%) and R3 ordering in I-S from Seilitz (>∼90%) and smaller illite percentage (∼70%) and R1 ordering in I-S from Kemmlitz. The clays never suffered a deep burial and there is no geological, petrographic or fluid inclusion evidence for aeolian input or hydrothermal origin of I-S at either deposit. The I-S formed exclusively at the expense of volcanic glass and not from K-feldspar. Residual quartz phenocrysts in the clays still preserve primary glassy silicate melt inclusions and lack secondary aqueous fluid inclusion trails. The dD and δ18O values of kaolinite and I-S are suggestive of low formation temperatures (<40ºC). Rb-Sr and K-Ar dating of I-S-bearing clay separates yield Lower Cretaceous ages at Seilitz and indicates the presence of excess or inherited 40Ar in illite-rich I-S. In contrast, Triassic to Jurassic Rb-Sr ages are obtained for I-S from the Kemmlitz kaolin deposit.

The use of disodium peroxodisulphate combined with a neutral buffer is a new method for the efficient removal of organic matter from clay-bearing sediments. The effects of this oxidation procedure on mineral structure were investigated by treatment of different standard clay minerals (kaolinite ‘china clay’, illite ‘Le Puy’, montmorillonite SWy-1). The materials were characterized by means of XRD, FTIR, SEM and TEM before and after leaching with disodium peroxodisulphate. Systematic experiments were conducted to determine the effects of leaching on the chemical and isotopic composition of oxygen, hydrogen and K-Ar in these samples. Effects on the physicochemical properties of the clays such as BET external surface area, cation exchange capacity (CEC) and expandability with ethylene glycol were also investigated. The results show that structure, chemical composition, oxygen and hydrogen isotope ratios, as well as the K-Ar system remain unaffected by leaching with disodium peroxodisulphate. The CEC and expandability remain unchanged, whereas changes in BET area can be attributed to mechanical dispersion by ultrasonic treatment.

Synthetic ferrihydrites with Si added at mass ratios of Si/Fe = 0, 10, 20, 40, 80, and 160 × 10−3 have been studied to examine the effect of Si on the properties of ferrihydrite. The Si proportionally reduces the point of zero charge but influences surface area, loss of weight to 800°C and solubility in acid oxalate solution to varying degrees. At a critical concentration of Si (when Si/Fe = 20 × 10−3) these measured properties indicate a greater particle size and a more ordered structure. The relationship between synthetic ferrihydrite and the surface of kaolinite has been studied by a combination of surface area and charge determinations and TEM. An attraction predicted at pH 3 between ferrihydrite particles and the basal surface of kaolinite has been confirmed, and resulted in a stable coating. However, at pH 6 any attraction between the minerals appears to be too weak to produce a coating of the kaolinite surfaces.

The expandability of K-depleted biotite and natural vermiculite was studied using transmission electron microscopy (TEM) and X-ray diffraction (XRD). K-depletion in layer-silicates was achieved by treating ultrathin sections with 0·1 m CaCl2 and BaCl2 solutions. The natural sample of biotite, which by XRD revealed no expandability on ethylene glycol or glycerol solvation, displayed 10–15% expanded layers when viewed by TEM after alkylammonium intercalation. The proportion of expanded layers increased after CaCl2 treatment. XRD of vermiculite samples revealed two sets of expandable interlayers after alkylammonium treatment, corresponding to two types of particles with different layer structures observed by TEM. Identification of vermiculite by TEM based on basal spacings is reliable with alkylammonium treatment. Intercalation of alkylammonium ions into the interlayers of vermiculite improved the degree of stacking order of the 2:1 layers.

The Japanese archipelago, in the temperate zone, has been affected by volcanic and hot spring action in many geological periods including the Recent one. Complicated clay mineral assemblages have been formed by alteration of volcanic glass both by weathering and hydrothermally, and have been studied by the writer and his collaborators (Sudo, 1950b, 1951; Sudo, Minato and Nagasawa, 1951; Sudo and Ossaka, 1952). The present account, based on these studies and on more recent data, deals with acidic to intermediate types of volcanic glass, which are widely distributed in rocks and soils throughout the islands.

The applicability of 27Al and 29Si magic-angle-spinning nuclear magnetic resonance (MASNMR) spectroscopy to the investigation of order-disorder in 1 : 1 dioctahedral layer-silicates was tested. 27Al and 29Si MASNMR showed the existence of short-range order in all these systems while XRD showed different degrees of long-range order-disorder. Spectra obtained on kaolinite and metakaolin clearly showed the transformation of some octahedral Al in kaolinite to tetrahedral coordination in metakaolin and also showed short-range Al and Si disorder in the latter. This suggests that structural re-arrangement on thermal treatment can be monitored by this technique. These results further suggest that MASNMR can detect short-range order, which is complimentary to the information that XRD provides regarding long-range order.

Lateritic weathering profiles developed on serpentinized peridotites of Murrin Murrin (Western Australia) exhibit thick smectite zones (10–15 m). The smectites from plasma and fissures were characterized by XRD, chemical analyses (ICP-AES, SEM-EDX and TEM-EDX) and Mo¨ssbauer spectroscopy. These Fe-rich smectites, previously described as nontronites, are in fact more complex. Their layer charges originate from both the tetrahedral and octahedral sheets. Plasma and notably fissure smectites exhibit, from the bulk sample scale to the particle scale, large and continuous Al for (Fe+Cr) substitutions, covering a chemical gap previously described for dioctahedral smectites ranging between nontronite and beidellite end-members. Lastly, they exhibit an octahedral occupancy slightly above 2, due to a low (Mg+Ni) trioctahedral contribution. Thus, the smectites occurring in weathering profiles of ultrabasic rocks can have actual chemistries intermediate between four dioctahedral end-members (beidellite, nontronite, montmorillonite and previously rarely described ferric-montmorillonite) and a trioctahedral one ((Mg+Ni)-saponite).