Description
An inorganic, reddish-blue powder pigment and one of the three synthetic ultramarines; The structure is a "three-dimensional aluminosilicate lattice" containing ionic sulfur groups. Azure blue is "derived from china clay by calcination." [Ullmann]
Sources/Uses
During the Middle Ages, ultramarine was used by artists as the "blue from over the sea." It was derived from the semiprecious stone, lapis lazuli, imported from Afghanistan. Since 1828 when it was first synthesized, the supply of the pigment has become abundant. Ultramarine pigments are used in plastics, paints, printing inks, paper, artist colors, laundry detergents (optical brightener), and toys. [Ullmann]
Comments
"A nuisance dust." [Sax] Safe in manufacture and use with the only known hazard being the evolution of hydrogen sulfide after contact with acid; it is not irritating, sensitizing, or mutagenic; [Ullmann]