👉 Calk is a type of mineral that is found in various geological formations, including sandstone, basalt, and limestone. It is composed primarily of calcium carbonate, which consists of calcium ions (Ca2+) bonded to carbon dioxide (CO2) molecules. This substance is used in various industrial applications, such as the production of cement, lime, and paper pulp. Calk can be extracted from the rock through a process called calcining. The process involves heating the rock at high temperatures to