Cobalt is a natural element which is actually silver, but when heated to extreme temperatures becomes the most beautiful blue known to man. It is the blue of the hottest fire. This blue was originally developed for porcelain in China and reserved for the very wealthy. It is still used in French dishes and glassware. It has been used for painting since 1700.
Have you ever mixed two colors according to the color chart and gotten some off color? It's because the pigment in the paint was not pure. Being a pure pigment, this blue will allow you to mix the paints and receive the desired color.
This rich, dark blue is used in many paintings of royalty for dishes, clothing, and jewelry.