Lapis Lazuli, a stone of a rich azure blue, often flecked with golden iron pyrites. It is a silicate, a type of rock consisting of silicon, oxygen, and one or more metals. The stone is used to make mosaics, vases, jewelry, and other ornamental articles. Lapis lazuli is about half as hard as the diamond. It was formerly used to make the pigment ultramarine. The stone is found in Asia, Chile, and California. It occurs mainly in crystalline limestone.