What is chalk made from?

According to Discovering Fossils, chalk is derived from lime mud that has accumulated in optimum conditions on the floor of the sea. Lime mud forms from the skeletons of microscopic plankton.

Chalk is a well-known rock formation and can be recognized by its white coloration, such as the Seven Sisters and the White Cliffs of Dover. For many years, chalk has been used for its chemical and physical properties in familiar products, such as blackboard chalk. Coccolithophores are considered to be the primary plankton that form chalk. Scientists have a great interest in chalk due to its interesting geological history.