M73246ssbauer spectroscopic evidence for akaganéite ( β -FeOOH) in New Zealand soils

Abstract

57Fe Mossbauer spectroscopy and computer-based data reduction procedures have been used to study quantitatively, the various secondary iron-containing minerals in a selection of New Zealand soils and iron-manganese soil concretions. The results indicate that akagankite (â-FeOOH), previously considered a rare mineral, is a major form of iron in these samples. Lepidocrocite (ã-FeOOH), and/or goethite (á-FeOOH) with a particle size less than approximately 70 A also appear to be present in all samples. Distinction between these two latter forms was not possible, because of the super-paramagnetic effects associated with fine particles of goethite. Hematite (á-Fe2O3 with a suitably large particle size (greater than approximately 180 A) was positively identified in two of the soil samples studied. The ratios of the concentrations of the various forms of iron are given.