The term ELEMENT IN CHALK can be solved by the crossword solution CALCIUM, which is a chemical element with the symbol Ca and atomic number 20. It is a soft gray alkaline earth metal that is essential for life on Earth. CALCIUM is the fifth most abundant element in the Earth's crust and makes up more than 3% of the Earth's crust. It is found in many minerals, including chalk, limestone, and marble. CALCIUM is also an important component of many biological processes, such as muscle contraction, nerve transmission, and blood clotting.