Calcium - EniG. Periodic Table of the Elements
Calcium is obtained from minerals like chalk, limestone and marble. Pure metal is produced by replacing the calcium in lime (CaCO3) with aluminium in hot, low pressure retorts. Calcium is used by many forms of life to make shells and bones, as a pure metal it has little use, however two of its compounds, lime (CaO) and gypsum (CaSO4), are in great demand by a nuer of industries.