The chemical formula of silicon dioxide is SiO2. Silicon dioxide has two forms, crystalline and amorphous. Silica, such as quartz and quartz sand that exist in nature are collectively referred to as silica. Pure quartz is a colorless crystal, large and transparent prismatic quartz crystals are called crystals, those with trace impurities and purple color are called amethysts, and those with light yellow, golden, and brown color are called smoke crystals. Chalcedony, agate, and jasper are colored quartz crystals that contain impurities. Sand is a fine particle of quartz mixed with impurities. Opal and diatomite are amorphous silica. If you are looking for high quality, high purity and cost-effective zinc sulfide, or if you require the latest price of zinc sulfide, please feel free to email contact mis-asia.