Lapis-Lazuli is a rock composed of several varieties of minerals in different proportions. Its colour is determined by the abundance of each of theses minerals in the rock fragment. There are Lazurite and Azurite for the colour ultramarine blue. Sodalite brings more of a blue-violet. The Haïyne gives a touch of translucent blue ocean. And the calcite gives the stones its white veining.

Another character of Lapis-Lazuli is to contain pyrite inclusions. Pyrite is a mineral species but made of sulfide iron, giving his famous golden sparks to the Lapis.

Its use dates back to at least 7000 years. In ancient Egypt, Lapis was one of the favourite ornamental stones, including carving scarabs. The stone was also reduced in powder ; we then drank it as an aphrodisiac "potion" during the Roman era. Or mixed with milk in the Middle  Ages, Lapis-Lazuli would warn the spirit of fear, doubt and envy.

As a powder, Lapis-Lazuli was also used as a pigment for tempera painting, to paint the sky ceiling of the Sistine Chapel for a nice example. This practice ceased in the early nineteenth century by the introduction of synthetic pigments, sometimes called French Ultramarine.

More Details