It is a chemical element with the chemical symbol Co and an atomic number of 27. Similar to nickel, it mainly exists in the form of compounds in the Earth's crust, except for a small amount of cobalt found in natural meteorite iron alloys. Pure cobalt obtained through reduction smelting is a hard, shiny, slightly brittle gray metal. Cobalt based blue pigments (such as cobalt blue) have been used in jewelry and painting since ancient times, as well as giving glass its unique blue hue. It is widely used in art and industry due to its stability and vibrant blue color. Cobalt compounds are also very important in ceramic and glass manufacturing, as they can produce various shades ranging from deep blue to light blue.