Fiber brucite is a unique natural hydroxide mineral fiber with the characteristics of strengthening, toughening, high-temperature resistance, and flame retardancy. It is widely used in fields such as construction, flame retardancy, and papermaking. The application of fiber brucite in high value-added products has important economic significance, and the application of fiber brucite is closely related to its mineralogical characteristics. The Heimulin fiber brucite deposit in Hanzhong, Shaanxi is currently the largest fiber brucite deposit in the world, and there is currently limited research on the mineralogical characteristics of fiber brucite in the region. By means of X-ray diffraction (XRD), X-ray fluorescence analysis (XRF), scanning electron microscopy (SEM), nitrogen adsorption desorption, and thermogravimetric analysis (TGA), this article studies the mineralogical characteristics and the changes in mineralogical characteristics of Heimulin fibrous brucite after heat treatment, providing a theoretical basis and scientific proof for the application of fibrous brucite, thereby further enhancing their economic value.