Origin: natural and artificialLapis lazuli is a complex rock mixture containing the mineral Lazurite (at Mineralogy Database)
Views of the mineral lazurite
Natural variety of pigmentNatural ultramarine is purifed from ground lapis lazuli by mixing it with wax and kneading in a dilute lye bath. The brilliant blue lazurite crystals preferentially wash out and are collected.
Artificial variety of pigmentArtificial ultramarine, also known as French ultramarine was made by heating, in a closed-fire clay furnace, a finely ground mixture of China clay, soda ash, coal or wood, charcoal, silica and sulfur. The mixture was maintained at red heat for one hour and then allowed to cool. It was then washed to remove excess sodium sulfate, dried and ground until the proper degree of fineness was obtained