Despite being the third most common element on the planet, the use of aluminium has been relatively short lived. This is because unlike iron, for example, aluminium is rarely found in a usable or natural state, and is very difficult to extract from other elements once they have bonded together.
In fact aluminium can be found in over 270 minerals in rocks or soil, purely as a result of its high reactivity to the oxygen that can be found in the air and in the ground. The most common source of aluminium is an aluminium ore called Bauxite, which sits fairly close to the earth’s surface. Before being converted into aluminium it is processed into a midway point that is neither bauxite nor aluminium, called alumina.
Alumina is a white powder, finer than table salt, and is made by grinding the bauxite and mixing it with lime (a type of calcium) and lye (a corrosive alkali) before placing it into high-pressure containers and heating the mixture up. Alumina is also known as Aluminium Oxide, because of the level of oxygen that is involved in its make-up; roughly 3 parts of oxygen, 2 parts aluminium.
Aluminium oxide can be used in this state, and does not have to complete the transition to aluminium to have useful applications:
In its pure form aluminium is a soft and durable metal with a silvery hue and good electrical and thermal conductivity. Additionally, when exposed to air a thin film of aluminium oxide forms around it, giving it a resistance to corrosive effects. These characteristics, along with several others, combine to make a material that is effectively 100% recyclable.
The reason aluminium is considered a young material is because it was completely unusable until the 1820’s, despite scientists knowing that the material existed over 150 years earlier. They knew this because aluminium belongs to a group of compounds called Alums, and when alumina was discovered as a component of aluminous soil in the 1500s, they knew that aluminium had to exist.