This book has introduced the current research status and significance of in-depth research on the heating transformation process of pyrite (see chapter “Current Research on Pyrite and Its Transformation Process”). Since the heating behavior of pyrite in air is more universal and applicable, as well as the reliability of XRD to study pyrite (England et al. 1999; Eneroth and Koch 2003; Yakovleva et al. 2003) and transformation processes in minerals (Ono 2007; Perrillat 2008), the author of this handbook takes natural pyrite as the research object and systematically analyzes the effect of different temperatures and constant temperature times on the magnetic susceptibility characteristics of heating products of pyrite using a magnetic susceptibility meter under heating conditions from room temperature to 1250 °C. Through XRD phase testing analysis, the magnetic change mechanism is further revealed. Its research results are not only beneficial to the study and application of rock magnetism (Li and Zhang 2005), paleomagnetism, and environmental science (Shi and Zhu 2000) but also provide a typical example for the study of the physical properties of heating transformation of metal mineral.