Electron relaxation in deerite

The mixed valence iron silicate deerite, Fe ₆ ²⁺ Fe ₃ ³⁺ O₃Si₆O₁₇](OH)₅ whose crystal structure has only recently been fully determined, had been previously examined by both susceptibility measurements and Mössbauer spectroscopy. We reinterpret the Mössbauer measurements from Frank and Bunbury and show that all contradictions between the phenomena, observed in their experiments, and the mineralogical structure disappear when one accepts a thermally activated electron delocalisation associated with Fe²⁺ ? Fe³⁺ charge transfer.