Cobalt blue is a cool, slightly esaturated blue color, historically made using cobalt salts. It was discovered by Louis Jacques Thénard in 1802. The world leading manufacturer of cobalt blue in the 19th century was Blaafarveværket in Norway, led by Benjamin Wegner. It is extraordinarily stable. Chemically it is a cobalt(II) oxide-aluminium oxide, or cobalt(II) aluminate, CoAl2O4. Commercial production began in France in 1807. It is made by sintering the stoichiometric mixture of finely ground CoO and Al2O3 at 1200°C.