Four bands occur in the Mössbauer spectra of pelletal glauconites ranging in age from Cambrian to Oligocene. Components due to Fe3+ in the cis M(2) positions are visible in all the spectra but their shapes depend on the expanding layer content. In the spectrum of the Oligocene glauconite a very well-developed shoulder due to Fe2+ in the trans M(1) positions is observed. In the younger glauconites (15–20% expanding layers) the conventional assignments of the spectra indicate that Fe2+ occupies the trans M(1) positions, the cis M(2) positions being vacant. Conversely, in the Palaeozoic samples (~5% expanding layers) the cis occupancy significantly prevails over trans occupancy.

Polarizing microscope, electron microprobe and X-ray diffraction examination of minerals in a soil profile developed on a glauconite sand indicate that destabilization of glauconite can be a progressive process which appears to be the reverse of glauconitization. Glauconite in these soils appears to be destabilized into a mixed-layer glauconite-nontronite phase, which crystallizes as a plasma mineral. This material in turn is transformed into smectite+kaolinite+oxides. Loss of K and Fe is evident in whole rock as well as microprobe analyses of the samples. Thus glauconite can lose both Fe and K to aqueous solution during weathering, leaving aluminous clay minerals in the soil.

Une étude expérimentale des équilibres d'échange entre gel de composition (A,B)O-SiO2-nH2O et solution aqueuse (A2+, B2+) a été réalisée avec les couples (A,B) suivants: Mn-Mg, Co-Mg, Co-Mn et Cu-Ni. Les coefficients de distribution (A/B)gel/(A2+/B2+)sol obtenus sont énormes, l'élément A se fixant presque totalement dans le gel et n'apparaissant le plus souvent qu'en traces dans la solution. Le dosage de celles-ci par activation neutronique a permis d'atteindre le domaine des concentrations où ces gels présentent un comportement idéal (loi de Henry) et de mesurer avec une précision accrue les enthalpies libres standard des réactions d'échange correspondantes.

A naturally occurring hematitic iron oxide/layer-silicate complex has been found in red mottled patches of a deeply weathered granite in north-east Scotland. X-ray diffraction shows a basal spacing of 36 Å—also observable by high resolution electron microscopy—which expands to 40 Å with glycerol and contracts to 33·5 Å on heating. Selected area electron diffraction reveals a composite hematite/layer-silicate pattern with the a-axis of hematite parallel to the b-axis of the silicate. The IR spectrum of the complex clearly shows the contribution made by each of the components. The silicate, with bands due to OH stretching at 3602 cm−1, OH deformation at 855 cm−1, and Si-O stretching at 1085, 1035, 540 and 471 cm−1 resembles ferruginous pyrophyllite, while the hematite, with a perpendicular band at 647 cm−1, in-plane bands at 519, 438, 400, 302 and 227 cm−1 and a characteristic pattern of relative band intensities, is similar to a platy form of soil hematite. Electron microprobe analysis of individual particles gives the complex an (Fe + Al): Si ratio of 6:1, which is consistent with a structure made up of twelve octahedral sheets terminated on both sides by a silicate sheet. It seems likely that the complex developed from a siliceous ferrihydrite which became progressively more organized with geological time.

L'examen des textures de kaolins au M.E.B. apporte des données complémentaires utiles pour la compréhension de leur genèse. Les kaolins provenant d'une altération météorique ont une texture poreuse constitutée par de gros paquets de plaquettes hexagonales empilées de façon lâche ce qui les différencie nettement des kaolins d'origine hydrothermale dont la texture est compacte et la porosité faible. Les kaolins sédimentaires montrent une association de petites plaquettes accolées les unes aux autres quand on les volt suivant les plans de clivage, ou présentent une orientation plus ou moins marquée dans la direction perpendiculaire. Enfin I'observation des textures permet de mesurer I'influence et I'importanee de la diagenèse dans les dépôts argileux.

The morphology and fabric of kaolin weathered from a non-feldspathic mica-phyllite in Znojmo, Moravia, are illustrated in scanning electron micrographs. In contrast to accordion-like kaolinite books, or elongate halloysite(?) crystals, commonly developed from feldspar, the kaolinite from the mica-phyllite tends to be individually platy, with highly irregular edges resulting from multiple adjacent crystal comers and re-entrants. Irregular or impaired crystal growth of kaolinite from mica may be due to ‘poisoning’ of kaolinite crystals by vanadium that is common in mica.

Proportions of the component layers in randomly interstratified illite-smectites can be determined precisely in the presence of discrete illite if two reflections (at 15–16 and 31–32°2θ Cu Kα) are strong enough to be measured accurately. The method takes into account the variable thickness of the smectite-ethylene glycol complex and involves a correction for the interference from illite reflections.