Cobalt blue
Cobalt blue is a blue pigment made by sintering cobalt(II) oxide with aluminum(III) oxide (alumina) at 1200 °C. Chemically, cobalt blue pigment is cobalt(II) oxide-aluminium oxide, or cobalt(II) aluminate, CoAlO. Cobalt blue is lighter and less intense than the (iron-cyanide based) pigment Prussian blue. It is extremely stable and historically, has been used as a coloring agent in ceramics (especially Chinese porcelain), jewelry, and paint. Transparent glasses are tinted with the silica-based cobalt pigment smalt. Historical uses and production. Cobalt blue in impure forms had long been used in Chinese porcelain. The first recorded  use of "cobalt blue" as a color name in English was in 1777. It was independently discovered as a pure alumina-based pigment by Louis Jacques Thénard in 1802. Commercial production began in France in 1807. The leading world manufacturer of cobalt blue in the nineteenth century was Benjamin Wegner's Norwegian company Blaafarveværket ("blue colour works" in Dano-Norwegian). Germany also was famous for production of it, especially the blue colour works ("Blaufarbenwerke") in the Ore Mountains of Saxony. In human culture. Art Automobiles Construction Sports Vexillology Video games Toxicity. Cobalt blue is toxic when ingested or inhaled. Its  use requires appropriate precautions to avoid internal contamination and to prevent cobalt poisoning. Natural occurrence. A single record of the compound concerns inclusions in sapphires from a single site.