Calcium at a glance

Fifth most common element in the earth's crust, important for bones and teeth, often asked in crossword puzzles, ... - ...which silver-white metal is meant? And what does your body have in common with a stalactite cave?

We are talking about calcium: a mineral whose importance we often only notice when it is missing in our body...

Calcium is a very common element. With the atomic number 20 and the element symbol Ca, it is familiar to us from crossword puzzles and chemistry lessons. Calcium is an alkaline earth metal, a shiny light metal with only a low density. However, it only occurs in bound form because it reacts strongly with other elements - which is why we know calcium mainly as a component of minerals. Depending on which other element calcium reacts with, well-known compounds such as marble or gypsum or less well-known compounds such as dolomite are formed. Together with magnesium, calcium in the form of carbonates makes up water hardness. Everyone who has left their coffee machine or tap to the deposits from the water for a long time knows how stubborn it can be.

But lime deposits can also show their most beautiful side, namely as stalactites and stalagmites in a dripstone cave. They are formed in calcareous soil under the influence of acid rain. This dissolves the lime in the soil, creating caves in the rock. As water drips down, sinter tubes form in which salts dissolved in the water crystallise out: A stalactite is formed. A stalagmite gradually grows at the bottom due to the water dripping on it. This is how the typical formations of a stalactite cave develop over the course of centuries.

Occurrence

Because of its abundance, we encounter calcium almost everywhere. Often we do not even notice it consciously. This is because it occurs almost exclusively in compounds that do not obviously bear the word calcium in their name. Or does it immediately pop into your head when you're hiking through the Alps that you're just walking over the same element that is so important for your body in the limestone Alps? Calcium-containing minerals are everywhere....

Properties

Calcium is a metal with a slightly shiny surface - silvery and crystalline. It is a very good conductor of electricity and heat, so it is also interesting for technology and business.

As for hydroxyapatite - the mineral from the class of phosphates, arsenates and vanadates (classification according to Strunz), which is so important for our body - it is less common than the other calcium compounds. Hydroxyapatite is formed from rock by high pressure and temperature in its environment, this often happens deep in the earth. In different rocks it can form by sedimentation, for example when particles from liquids are deposited. Think about it the next time you are in the Fichtel or Erzgebirge mountains, or spend your holiday on Lake Maggiore... everywhere there has been a major occurrence of hydroxyapatite.

Biomineralisation takes place in living organisms. This is a process in which mineral products are formed in a body. More than 50 per cent of the bones of vertebrates - including us humans - consist of hydroxyapatite, a calcium phosphate that is made up of phosphate and calcium ions. It is no coincidence that calcium is also called a bone mineral.

The collagen, which is also present in about one third, causes the hydoxylapatite to crystallise and maintain its strength. When these crystals solidify, they align themselves according to tensile, pressure and tension forces, which in turn leads to a very stable and firm structure of the whole. Because of this strength and hardness, bones were already in great demand as indestructible tools and weapons in prehistoric times. We get an idea of the durability of these structures when we consider the long periods of time that fossil bone finds have already survived and will continue to survive. And it is precisely this substance that makes our bones strong and solid.

Hydroxyapatite is also the main component of tooth enamel - which is why it is so hard. The addition of fluoride ions gives it even more strength.

Use and function of calcium in chemistry and technology

• Calcium is a reducing agent. As such, it is used in the production of other metals.
• Important in the production of steel and aluminium.
• Basis for caustic lime
• In the form of chalk, calcium is a component of PVC and other plastics. It is used there for strength and stability.
• The conglomerate of calcium, oxygen and carbon - namely calcium carbonate - is often used for paper production.
• Feed lime, as the name already suggests, finds its application in animal husbandry.

Use and function of calcium in the human body

• Calcium is important for maintaining the strength of our bones and teeth. It prevents osteoporosis.
• Calcium contributes to the function of digestive enzymes and is partly responsible for muscle contraction.
• Calcium is important for the transmission of signals between the individual nerve cells in our body.
• Calcium is involved in cell division and also in blood clotting.

Calcium is abundant everywhere - so abundant that we often hardly think about it. Do you also take it for granted?

That can be a fatal mistake when it comes to our health. After this short digression and overview of calcium as an element and as a component of our environment, the following will deal with the following,

• what calcium does for your health
• how much calcium you should take in and where you can find it
• How you can recognise calcium deficiency and what you can do about it.

Curious now? The linked articles will give you more information on the individual topics.