Mössbauer effect and X-ray diffraction studies of synthetic iron bearing trioctahedral micas

Mössbauer effect, (ME) and powder X-ray diffraction, (XRD) have been used to study the relationship between cationic size, tetrahedral layer rotation, octahedral layer flattening, stability, and Mössbauer quadrupole splitting, qs, of iron bearing trioctahedral micas. Tetrahedral layer rotation accounts for much of the lattice adjustment but biotites that require an angle of rotation higher than 21 degrees are not stable. Both experimental and computational data show that qs for Fe³⁺ (IV) increases with increasing degree of tetrahedral layer rotation. A systematic increase of qs for Fe²⁺ (VI) is also observed, but this could be due to factors other than tetrahedral layer rotation.