Cobalt is a chemical element that is commonly found in the earth's crust in the chemically combined state. The free element obtained by reductive smelting is a metal that is hard and lustrous. The metal is silver-gray in color.  Nowadays, cobalt is mainly used as a metal to produce alloys. However, in the ancient period (prior to the nineteenth century), it was used as a pigment. A number of colors were made using cobalt and were used in paintings and glass coloring. The most famous colors that were used were cobalt blue and cobalt green. Cobalt based pigments were seen used in traditional jewelries as well. Cobalt blue pigments were widely used in paintings and artworks because its rich blue color is very attractive.