Between approximately 145 and 66 million years ago, a geological period known as the Cretaceous, large areas of the world as we now know it were covered by vast seas. Once dead, the marine animals sank to the bottom, where eventually nothing remained of them except their calcareous skeletons and shells. Over the years these formed thick layers, sometimes dozens of metres thick, which were crushed under the sediments of the sand and clay deposited by rivers. When later the sea level dropped and the Earth's crust was pushed upwards, these white layers reached the surface. They consist mainly of calcium carbonate, a form of calcite better known to us as chalk, the oldest white pigment on earth. The Dutch name for chalk ‘krijt’ and its French equivalent ‘crétacé’ reveal the origins of their names, the chalk cliffs of the island of Crete.
Apart from chalk (calcite) other white mineral pigments occur naturally. Examples include kaolin, also known as china clay or pipe clay, and gypsum. These whites have been used ever since man first started painting. Chalk can be found, for example, in the oldest cave paintings, and primitive tribes even today paint their bodies with paints, including white, according to age-old rituals.