The observation of an ''electron hopping phenomenon'' in ilvaite, CaFe22+Fe3+ Si2O8(OH), has been made by previous workers. The effect of temperature on Fe2+→Fe3+ electron delocalization in ilvaite is closely investigated in the present study. M¿ssbauer spectra of a suite of naturally-occurring ilvaites were recorded over a range of temperatures, 80K to 575K. Delocalization is readily confirmed in the spectra with appearance of species with parameters intermediate to Fe2+ and Fe3+. Contrary to prior investigations, five doublets are required to fit the spectra and are assigned to Fe3+(A), Fe2+(A), Fe2+(B), and Fe2+(A) →Fe3+(A) ∥c and ⊥c. Doublets associated with delocalization are resolved at 80K and preclude the use of an order-disorder transition model. We propose a thermal activation model and draw some implications for geophysical applications.