Structural variation of babingtonite depending on cation distribution at the octahedral sites

Abstract

Babingtonite from six localities, and manganbabingtonite from Iron Cap mine were studied using EMPA, ⁵⁷Fe Mössbauer analysis and single-crystal X-ray diffraction methods to determine the cation distribution at octahedral sites and to analyze its effect on the crystal structure of babingtonite. As the results of Mössbauer analysis, Fe²⁺ and Fe³⁺ are assigned to M1 and M2, respectively. The <M1-O> distance increases with increasing mean M1 ionic radius. The lengthened M1-O13 distance leads the positive correlation between Si1-O15-Si5 angle and M1-O13 distance. The increase of Si1-O3-Si2 and Si4-O12-Si5 angles due to the increase of mean M2 ionic radius is also observed.