Evidence for loss of protons and octahedral iron from oxidized biotites and vermiculites

作者：Victor C. Farmer, James D Russell, W. J. McHardy, A. C. D. Newman, James L. Ahlrichs, J Y H Rimsaite · 发表于：Mineralogical Magazine · 年份：1971 · DOI：10.1180/minmag.1971.038.294.01 · 被引用次数：141 · 研究领域：Iron oxide chemistry and applications、Clay minerals and soil interactions、Radioactive element chemistry and processing

Summary Infra-red examination of a weathered biotite and of biotites that have been converted to vermiculites and subsequently oxidized, indicates that oxidation of octahedral ferrous ions to ferric ions is associated with a reversible conversion of hydroxyl ions to oxide ions. Subsequently, in high-iron biotites, there is an irreversible loss of ferric ions from the octahedral layer, resulting in an increased number of dioctahedral sites. Electron microscopy and X-ray diffraction indicate that ejected ferric ions form either amorphous interlayer oxides or, when bromine is used as an oxidant, a crystalline external phase of β-FeOOH. The high refractive index of some oxidized vermiculites is shown to be due largely to submicroscopic iron oxides.