Crayons today are made from clay—a fine-grained, heavy soil—the same material as is used for making many pots. The clay is mixed with a pigment, to give it colour, and wax to prevent it drying out. Hundreds of colours are now available.
Before wax crayons were made, the most popular form were called chalks. White chalk was made from the stone of the same name (a form of limestone), black chalk from shale and red chalk from red ochre. The stone was ground, mixed with a liquid to bind it together and then dried into sticks. Pastels, which can come in many colours, are mixed with gum rather than wax or water.
Limestone was built up under the sea over millions of years from the shells of tiny creatures called formanifera, which settled on the sea floor after they died and built up in a layer miles thick.