Iron is a chemical element (Fe) with an atomic weight of 55.845 and sits on the periodic table between manganese and cobalt, atomic number 26.
A universal element
Iron is an element abundant throughout the Universe; the heaviest element that can be made by nuclear fusion. Nuclear fusion takes place in stars, and when a star eventually goes supernova and explodes, iron is blasted into the Universe.
The Earth’s solid central core and the liquid outer core of our planet are both nearly 80% iron. The outer core is the layer that gives Earth its protective magnetic field that helps to protect all life on Earth from cosmic radiation.
The constituent parts of Earth. Our planet’s outer core is a fluid layer of mostly molten iron with an estimated temperature of 3,500 degrees centigrade.
The central core of Earth is basically an enormous magnet. This magnet is not only useful to humans; birds are thought to use it to navigate vast distances around the world. One theory suggests that birds have eyes that are adapted to be able to see the magnetic field. It must be like having a built-in sat-nav system!
Iron in humans
Iron is everywhere on Earth; it is part of the fabric of our world. As I write this article, my own body contains around 4 grams or three-quarters of a teaspoon of iron. Multiplied over the entire 7.7 billion people that make up the human race, that adds up to approximately 30,000 metric tonnes of the metal.
Iron is an essential mineral for human beings as it helps to transport oxygen around the body. If we are deficient in iron our body is unable to make enough red blood cells to carry all the oxygen we need from the lungs to other parts of the body, resulting in fatigue. 70% of the iron we contain is found in our blood, which is red because of the interaction between iron and oxygen.
Red blood cells flowing through the human body. Iron is needed by humans to produce haemoglobin, the substance in red blood cells that transports oxygen throughout the body.
Every single living organism on our blue planet contains traces of iron… except one. The bacterium Borrelia burgdorferi. This tiny but dangerous bug gives us lime disease and swaps out its iron and replaces it with magnesium. It is the only life form on Earth that is iron-free.
Iron’s use in warfare
Iron has a long, complicated and extremely violent history with the human race. We first smelted iron around 1500BC in what is now modern Turkey. We made tools and weapons from it, and we still do. These Turks (Hittites) kept the process to themselves for 300 years, during this time a warrior with an iron blade was almost invincible.
Throughout history, iron has been used to kill millions of people and we continue to use it for this purpose. There is an old saying that iron, like fire and water, makes a good servant but a bad master.
A small English Civil War-era cannon. Cannons are one of the many weapons that humans have cast from iron for use in warfare over the centuries.
Iron makes up around 90% of all the metal refined on Earth each year. We use iron in every imaginable product, from ships to bridges and virtually all construction projects.
Iron is valued for its strength which is derived from its cubic crystalline structure. It does contain some defects in its crystal structure, however, smelting iron at high temperatures makes the crystal structures smaller and more consistent, leading to a much stronger material.
The Eiffel Tower in Paris, designed by Gustave Eiffel and completed in 1889. It was constructed from wrought-iron girders and marked the entrance to the World Fair.
The relationship between iron and steel
Iron is also the basis of steel. You can give a very concise definition of steel by describing steel as iron alloyed with carbon, usually with less than 1% carbon. Steel can then be made into various grades of stainless steel alloys by adding other metals such as chromium and nickel. These added metals make the steel more corrosion-resistant and less brittle to become stainless steel.