Lapis lazuli is defined as a rock of varying composition. The following minerals have been identified in this rock by X-ray diffraction: lazurite, haüyne, sodalite, nosean, mica, diopside, wollastonite, calcite and pyrite. Among them the first two minerals, lazurite and haüyne, are responsible for the unique blue colour of massive lapis lazuli [1]. As it has been proved [2], the blue colour of ...