Lapis lazuli is known by many as the stone of friendship and truth, and has been regarded by some cultures as a holy stone. It is an opaque gem with gold flecks (iron pyrites) and calcite. Throughout history it has been highly prized. Some of the earliest examples of its use is in ancient Egyptian jewellery. Ground lapis lazuli was used by artist's as a pigment, as so is part of countless Old Master paintings, until it was replaced by synthetic ultramarine in the nineteenth century.