The chemical formula of Silicon Dioxide SiO2 is SiO2. Silicon Dioxide SiO2 has two forms, crystalline and amorphous. Silica that exists in nature, such as quartz and quartz sand, is collectively referred to as silica. Pure quartz is a colorless crystal, the large and transparent prismatic quartz crystal is called crystal, the purple one containing trace impurities is called amethyst, and the light yellow, golden and brown is called smoky crystal.

Chalcedony, agate, and jasper are all colored quartz crystals that contain impurities. Sand is fine grains of quartz mixed with impurities. Opal and diatomaceous earth are amorphous Silicon Dioxide SiO2. Silicon Dioxide SiO2 has a wide range of uses, mainly used for making glass, water glass, pottery, enamel, refractory materials, aerogel felt, ferrosilicon, molding sand, elemental silicon, cement, etc.