The interaction of ammonia with Na—, NH4—, Ca—, Cu—, and Mg— forms of two vermiculites has been investigated by infrared spectroscopy and chemical analysis. Both NH4 ions and co-ordinated NH3 are produced in the interlayer space in amounts which depend on the exchangeable cation and the particle size of the vermiculite. With the exception of that in Cu-vermiculite, the co-ordinated NH3 is rapidly displaced by atmospheric water vapour. NH4 ions are slowly decomposed at normal humidity and more rapidly and completely at high humidity. The co-ordinated NH3 in Cu-vermiculite is converted to NH4. Relative amounts of NH4 and co-ordinated NH3 are influenced by particle size, smaller particles favouring NH4. The stabilities of both species to water vapour increase with particle size.

Following the work of Davis & Worrall (1971) the adsorption of glucose from aqueous solution on sodium kaolinite has been re-examined. Colorimetric and radiochemical methods were used for glucose assay. Adsorption is very small and is probably positive.

Volcanic ash soils were studied with the scanning electron microscope to observe the morphology and occurrence of allophane, imogolite and halloysite. Allophane and imogolite in general were randomly distributed indicating a process of dissolution and recrystallization. Halloysite is typically associated with feldspars showing that it is formed by direct alteration.

The imogolite fibres studied with the SEM show them to be much thicker than currently reported in the literature and it is thought that pretreatment of the clays for TEM measurements results in a partial destruction. Halloysite consists typically of short rigid tubes and thus differs from imogolite which tends to curl.

Fixation of K by some West Indian soil clays was proportional to their montmorillonite contents. Reductions in c.e.c. and surface areas occurred after fixation. The reductions in c.e.c. were equivalent to the amounts of K fixed, suggesting that an ion exchange mechanism was operative. Reductions in c.e.c. were proportionately greater than reductions in surface area.

Release of native K from the clays was greater from the < 0-2 μm fractions than those from 0·2−2·0 μm. Appreciable amounts of'recently fixed' K were not released after extraction with 0·03 N NaCl solution. Removal of 'free' iron increased the release of: (i) native K from the 0·2−2·0 μm fractions ; and (ii) 'recently fixed' K from both fractions. The presence of NH4 ions decreased the release of 'recently fixed' K.

The release pattern of the clays indicates that intra-particle diffusion rather than film diffusion or mass action exchange, is the rate-limiting mechanism.

X-ray analyses indicate that illite, smectite, loughlinite (Na20.3Mg0.6SiO2.8H2O) and chlorite are present in the < 2 μm fraction of the lacustrine Green River Formation (Eocene) of Wyoming. Material amorphous to X-rays and random mixed-layer structures are present in subordinate amounts. Individual crystals vary from pure, well-ordered structures to poorly crystallized forms.

Illite is ubiquitous, occurring in all the samples studied. It is generally associated with other clay minerals but frequently occurs as the only clay mineral found in the 'oil shales'. Smectite is present in all three members of the Green River Formation, but its presence frequently shows an inverse relationship to both analcime and loughlinite. Loughlinite is restricted to the saline facies of the Wilkins Peak Member. Chlorite occurs only in the silty and sandy beds of the Tipton Shale Member. The distribution of random mixed-layer structures and amorphous material is irregular. Several independent lines of evidence favour an in situ origin for many of the clay minerals reported in this investigation.

The 'oil shales', which are in most cases varved, kerogenous, dolomitic marls, have a variable clay mineral composition. There is a marked tendency, however, for illite to be the dominant or the only clay mineral present. Apparently the geochemical conditions favouring the accumulation of the oil shales also favoured in situ generation of illite.

The Cretaceous fuller's earth of Southern England has been studied using sedimentological, petrographical and X-ray diffraction techniques, and by 40Ar-39Ar radiometric dating. The results indicate that the ultimate sources of the fuller's earth were basic to intermediate, alkaline pyroclastic materials, perhaps stemming from volcanicity associated with the Mesozoic rifting of the North Atlantic. The Wolf Rock phonolite is considered as a potential pyroclastic source. Deposition occurred under normal sedimentary processes, with partial re-working of land-fall ash, and incorporation of orthoclastic debris.

The soils examined are from alluvial sheet deposits in a high valley where they are subjected to alternate wetting and drying, leading to desiccation. They are principally derived from shale and limestone bedrock in the surrounding mountains which are rapidly eroded and transported down valley mainly when the snow melts. The soils have engineering properties of fairly low density, high permeability, high plasticity with the plasticity index above the A line (CH range). These properties are correlated with the size grading and the clay mineralogical composition – about 30% calcite, 45-50 % clay minerals, dominated by Fe3+ and Mg-smectites and fine-grained muscovite. The clay mineralogy is explained in terms of Millot's zone of smectitization affecting biotite from detrital shale fragments, the muscovite remaining substantially unaltered. Calcite solution and redeposition account for the chalky texture and strong bond.