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The magnetic structure of hematite is affected by the mechanical processes of cutting and lapping thin slices or plates of natural single crystals for Mossbauer absorption measurements. The effect, as observed in plates perpendicular to the basal plane, is to produce an anisotropic Fe3+ spin distribution in which the total spin component in the plane of the plate is less than that normal to the plate. The anisotropy is removed by annealing. Magnetic fields of 10 kOe produce no remanent changes in the spin distribution either before or after annealing. This implies, and measurements confirm, the existence of an accompanying directional dependence in the remanent magnetization. The effect is attributed to deformation twinning which results from stresses imposed during sample preparation.

Evidence is presented which suggests that the adsorption sites necessary to initiate the formation of the δ-phase (Co+2 ions occupying positions in the structure of the support) in supported cobalt catalysts are acid sites. In addition the δ-phase is found to be more difficult to reduce than the β-phase (Co3O4), and the presence of a competing ion (Ni+2) in the impregnating solution is found to increase the proportion of cobalt in the-phase. The assignment of octahedral coordination to the Co+2 ions in the δ-phase follows from measurements of the Co k-absorption edge in spinel-type compounds.

Crystallites of two different orientations have been observed in the polycrystalline magnetite layer formed by carbon monoxide reduction on the basal plane of a hematite single crystal. The relative reducibility of hematite and magnetite ores may be related to this double orientation.