Calcium makes our bones and all the bones and nearly all of the shells of other living things.

Because calcium is so important to living things, they all make sure they get enough of it, as otherwise they would not be able to have healthy bones and shells. Calcium is found in many plants, and so most animals get all the calcium they need from eating plants (or other animals that originally ate plants). That is how we get our calcium, too. Babies get their calcium by drinking their mother's milk, and we can get calcium from drinking cow's milk.

Calcium is found in rocks such as chalk and limestone. It is ground up and heated and used to make cement. It is crushed to make sticks of writing chalk.

Calcium is important in rocks, such as limestone and chalk, both of which are calcium carbonate. Crystals of calcium minerals are very beautiful and are known as calcite. They are shown in the videos below.