Alkali fusion purification is one of the fine purification techniques used in mineral materials. Its basic principle is that based on the solubility of common minerals in acid or alkali solutions, they can be classified into four types (see the chapter “Acid-Alkali Resistance of Minerals,” Tables 1 and 2): alkali-resistant but acid-soluble minerals, acid-resistant but alkali-soluble minerals, minerals that are neither acid-resistant nor alkali-resistant, and minerals that are both acid-resistant and alkali-resistant. Therefore, based on the differences in chemical properties between valuable minerals and impurity minerals in mineral raw materials, impurity minerals can be removed to achieve the fine purification of valuable minerals. Now, examples are shown as follows.