• journal_title：American Mineralogist
• Contributor：G. Artioli ; C.A. Geiger ; M. Dapiaggi
• Publisher：Mineralogical Society of America
• Date：2003-
• Format：text/html
• Language：en
• journal_abbrev：American Mineralogist
• issn：0003-004X
• volume：88
• issue：7
• firstpage：1084
• section：Articles

The crystal structure of julgoldite-Fe³⁺ from Bombay, India, was investigated by ⁵⁷Fe Mössbauer spectroscopy and synchrotron X-ray powder diffraction. Only ferric iron was detected in the Mössbauer measurements and it occurs at two different octahedral sites in the atomic ratio 20:80. Based on Rietveld refinements, the Fe³⁺ cations are located at the X- and Y-octahedral sites with atomic percentages of about 25% and 75%, respectively. The resulting chemical formula of the Bombay julgoldite sample is Ca₈(Fe_2.7³⁺Al_1.1Mg_0.2)(Fe_8.0³⁺)Si₁₂O₄₂(OH)₁₄. The oxidation state of Fe is not the same as that arrived at through simple crystal-chemical considerations. Such analysis cannot give quantitative results for the valence state of mixed-valence cations in pumpellyite-type minerals and their intracrystalline partitioning behavior. Assignments of the Mössbauer absorption doublets and an analysis of Fe-intracrystalline partitioning behavior are discussed with reference to previous works on different pumpellyite-type minerals.