Magnetite is the most magnetic of all the naturally occurring minerals on Earth. Naturally magnetized pieces of magnetite, called lodestone, will attract small pieces of iron, and this was how ancient man first discovered the property of magnetism. This book gathers and presents current research from across the globe in the study of magnetite; its structure, properties and applications. Some topics discussed, herein, include adsorption and magnetothermal phenomena of high-disperse magnetite; electrochemical properties of magnetite and its role in flow accelerated corrosion; the unique structures and properties of magnetite and its relevance to biology and biotechnology; the synthesis methods of magnetite particles in wet chemistry; and magnetic hyperthermia studies in magnetite ferrofluids.