Cobalt blue
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. The leading world manufacturer of cobalt blue in the 19th century was Benjamin Wegner's Norwegian company Blaafarveværket ("blue colour works" in Dano-Norwegian). Germany was also famous for production, especially the blue colour works ("Blaufarbenwerke") in the Ore Mountains of Saxony.
Blue billy
The name is a reference to its distinctive bright blue colour, which can make it immediately obvious in other mud or soil. Chemically it is a form of Prussian blue. Although several chemical industry processes could produce it, it is particularly associated with coal gasification and older town gasworks. It has been recognised as a problem effluent and land contaminant since the early industrial period and the first gasworks at the start of the 19th century.