Natural chalk is made up of prehistoric saltwater organisms high in calcium that formed rock-like sediment. There is no inventor. Chalk-based materials have been used in writing for centuries, with no known inventor.
Scotland's James Pillans is often credited with the invention of colored chalk as well as the blackboard. He taught geography and was headmaster of the Old Royal High School in Edinburgh, Scotland. Pillans' recipe for colored chalk included ground chalk, color dyes and porridge. Chalkboards had made their way into almost every classroom by the mid 1800s. The invention of cork boards for presentations did not occur until 1891.