A Class I lodestone is a massive iron ore which owes its magnetic hardness to oxidation. Oxidation of the Fe3O4results in a fine intergrowth of &ggr; Fe2O3in host Fe3O4, a requisite for all lodestones studied. The natural remanence (NRM) to saturation isothermal remanence (ISR) values are ≳0.5 compared to values <0.05 for most other naturally magnetized materials. The behavior of the lodestone magnetization has been studied from 4 K to 825 K, and x‐ray, optical and transmission electron microscopy data have been used to confirm the &ggr;‐FeO3‐Fe3O4epitaxy. On heating to 250 °C coercive force (HC), remanent coercive force (HR), and ISRdecrease, while about 70&percent; of the NRM is lost. On returning to ambient temperature an increase in saturation magnetization (IS) is noted which can be interpreted as an ordering of the &ggr; Fe2O3. Further heating to 425 °C results in destruction of the &ggr; Fe2O3, a complete destruction of the lodestone remanence, while Hc, HR, and ISRincrease. Beyond 425 °C the material behaves normally. On returning to ambient temperatre Hcand HRrecover in smooth and continuous fashion while the thermoremanence (TRM) acquired in the geomagnetic field is less than 5&percent; of the NRM value. Initial and final HCand HRvalues are the same. However as the thickness of the &ggr; Fe2O3lamellae increase the final HCand HRvalues are reduced. ISis reduced by an amount dependent on the &ggr; Fe2O3?&agr;Fe2O3conversion. The intense lodestone remanence was apparently acquired during the oxidation of Fe3O4, though the lodestone could be charged by fields associated with a lightening discharge.