A natural inorganic blue pigment with slight red cast made from the ground, separated blue particles (lazurite) from the gemstone lapis lazuli. It has good fade resistance, fair transparency, but poor resistance to acids. It was the most expensive pigment in Western Medieval and Renaissance painting and manuscript illumination, generally reserved for the robe of the Madonna or another prestigious figure. It darkened with age, thus the synthetic variety was developed in the 19th century; blue deposits on the walls of lime kilns had been used earlier to produce a similar pigment, "artificial ultramarine blue."
