"Azurite is the oldest blue pigment, almost used worldwide long before lapis lazuli. Azurite, also known as Chessylite or Mountain Blue, is a natural basic copper carbonate. The beautiful deep blue mineral occurs in the oxidation zone of copper deposits, together with chrysocolla and malachite, it’s more oxidized form. Azurite forms deep blue translucent crystals. The purer and larger the crystals, the darker and more intense the color. At first grind, azurite is a pale greyish-blue color. However, complex wet processing techniques and the subsequent particle separation offers a wide palette of different hues ranging from deep dark blue to brilliant azure. From the 15th to the 17th century, azurite was no doubt the most important blue pigment in European painting, mostly used in tempera. In paintings of that period, it is found more frequently than ultramarine, often serving as its less costly underpaint. The use of smalt, and even more so the invention of Prussian blue in the 18th century seem to have displaced azurite from the artist palette in Europe. In the past, important sources for azurite where the copper deposits near Athens, Rudabanya (Hungary), Lyon, and Innsbruck. Today, azurite comes from e. g. Namibia, France, Marocco, China, and the USA.“ -Kremer Pigments. More information is available on their website, so please consult their materials for more complete information about this pigment.