Calcium makes about 3.6 per cent of the Earth’s crust. But it is rarely found as a free metal. Calcium is abundant on the surface of the Earth and is mostly found as chalk, limestone, or marble.
Let us now look at how these calcium deposits are formed. The shells of living things in the ocean are made of calcium carbonate. When they die, they sink to the bottom of the ocean. Over the years, these form layers of sediments. As the layers build up, their weight squeezes the water trapped between and they stick together. Over thousands of years, the shells are transformed into sedimentary rocks called chalk, limestone and marble.
It was Sir Humphry Davy who isolated calcium for the first time in 1808.
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