Chalk is a soft, white, porous sedimentary rock made primarily of calcium carbonate. It is formed from the accumulation of tiny marine organisms' shells over millions of years. Chalk is commonly used in classrooms for writing on blackboards, as well as in art for drawing and sketching. In addition to its educational uses, chalk has applications in various industries. It is used in the production of cement, as a filler in products like paint and rubber, and even in agriculture to improve soil quality. Chalk is also a popular material for sports like rock climbing and gymnastics, where it helps improve grip.