Calcium is one of the most abundant minerals on earth – it’s the most common mineral in the human body and has a host of industrial uses.
This silvery-white, soft metal is the fifth most abundant mineral in the Earth’s crust. It tarnishes rapidly in air, reacts with water and is the third most common metal after iron and aluminium. It is the main ingredient in limestone.
Put simply, the world would be a very different place without it.
Calcium in the human body
Calcium is vital to the health of muscles, ease of digestion and the circulatory system.
However, it is in building our bones and teeth for what calcium is best known and vital for. Calcium phosphate is the main component of bone and the average human contains about 1 kilogram of calcium.
To promote bone growth, children and pregnant women are encouraged to eat foods rich in calcium, such as milk and dairy products, leafy green vegetables, fish and nuts and seeds.
How calcium behaves
Calcium is safe in its ionic form in the body, but it is highly reactive with water, forming hydrogen and calcium oxide.
For this reason, metallic calcium must be stored in oil to avoid any moisture reacting with the calcium.
The metal is also very soft, you could cut through it with a butter knife with ease - however it will rapidly oxidise, meaning it will lose its dull shine to a more grey/white color.
How we use calcium
Calcium has been used for generations in plaster, found as far back as 7000BC in models and sculptures and is still commonly used today for the exact same reasons. However, a metallic calcium sample was not isolated and identified until 1808 by the scientist Humphry Davy.
In medicine, calcium is used for finding bone diseases such as osteoporosis, which results in a reduction in mineral content in the bones. The disease can also be treated with calcium supplements.
Because it reacts strongly with Sulphur and oxygen, it is ideally used by the steel industry. These elements float to the top of molten steel and can be easily removed by combining with calcium, leaving the liquid steel behind.
The aluminum industry also uses calcium to harden aluminum into an alloy. This process is effective because the large calcium atoms break up the soft structure of the aluminum.
Calcium in the natural environment
Calcium is not found in its ‘pure’ form in nature, but occurs abundantly as limestone (calcium carbonate), gypsum (calcium sulfate), fluorite (calcium fluoride) and apatite (calcium chloro- or fluoro-phosphate).
Hard water contains dissolved calcium bicarbonate. When this filters through the ground and reaches a cave, it forms stalactites and stalagmites.
Calcium metal is prepared commercially by heating lime with aluminum in a vacuum.