LAPIS LAZULI is a metamorphic rock containing three minerals in varying amounts: lazurite, calcite, and pyrite. This ancient gem is formed during the metamorphosis of chalk into marble.
Lapis Lazuli has been prized since antiquity for its intense blue color, and has been mined since 7th Millennium BC from a number of mines in the area of Afghanistan. Beads of this semi-precious stone have been found at a number of Neolithic burials as far from Afghanistan as Mauritania, and it was also used in the funeral mask of King Tutankhamun (image below from wikipedia.com).
At the end of the Middle Ages, it began to be exported to Europe, where it was ground into powder and made into ultramarine, the finest and most expensive of all blue pigments, which was used by some of the most important artists of the Renaissance and Baroque.