Lepidocrocite (gamma-FeOOH), prepared using several different aging temperatures and aging times, possesses widely varying morphological and structural features. Mean particle dimensions and surface areas were all found to depend on the conditions of the synthesis. Studies of the aqueous reduction of several of the lepidocrocite samples to magnetite indicated that the initial steps in the dissolution-reprecipitation process were influenced by the crystallinity of the material. Results of the morphological studies and the transformation reaction studies are described within the context of corrosion-product generation and stability in secondary feedwater systems of pressurized heavy-water nuclear reactors.