Aluminum silicate is a silicate. Its chemical formula is Al2SiO5. Because most of the silicate structure is very complex, it is not written in the form of salt, but is written in the form of metal oxide. Therefore, aluminum silicate is often written as Al2O3. SiO2. The density of aluminum silicate is 2.8 to 2.9 g / cubic centimeter, and the refractive index is 1.56. The MOhm hardness is related to the type of ore and water content, and changes between 4.5 and 7.5. Aluminum silicate powder is often used as a fireproof material, such as a glass kiln used in the glass industry.