Why is cobalt blue?

It's a cobalt oxide-aluminum oxide. Very costly and extraordinary stable pigment of pure blue colour discovered by Thénard in 1802. It is now the most important of the cobalt pigments. read more

Cobalt blue in impure forms had long been used in Chinese porcelain, but it was independently discovered as a pure alumina-based pigment by Louis Jacques Thénard in 1802. Commercial production began in France in 1807. The first recorded use of cobalt blue as a color name in English was in 1777. read more

Cobalt as a naturally occurring element is not blue but instead, silver. The metal you are referring to is a mixture of aluminum and cobalt which is often used as a pigment in pottery, painting, and jewelry. read more

Very costly and extraordinary stable pigment of pure blue colour discovered by Thénard in 1802. It is now the most important of the cobalt pigments. Although smalt, a pigment made from cobalt blue glass has been known at least since the Middle Ages, the cobalt blue established in the nineteenth century was a greatly improved one. read more

Cobalt blue is a blue pigment made by sintering cobalt oxide with alumina at 1200 °C. Chemically, cobalt blue pigment is cobalt oxide-aluminium oxide, or cobalt aluminate, CoAl2O4. Cobalt blue is lighter and less intense than the pigment Prussian blue. It is extremely stable and has historically been used as a coloring agent in ceramics, jewelry, and paint. Transparent glasses are tinted with the silica-based cobalt pigment smalt. read more