Iron is a metal extracted from iron ore; iron is almost never found in the free (elemental) state. In order to obtain elemental iron, the impurities must be removed by chemical reduction. Iron is used in the production of steel. Steel is not an element, but is instead an alloy, or a solution of different metals (and some non-metals, particularly carbon).
The nucleus of iron has the smallest amount of energy per nucleon, so it is the heaviest element that is produced exothermically through fusion and the lightest through fission. When a star that has sufficient mass to produce iron does so, it can no longer produce energy in its core and a supernova will ensue.
The extraction of iron
Iron is extracted from the ore Hematite, which is mainly Fe2O3. The iron is seperated from the ore by reduction with Carbon - a more reactive element. This process takes place in a blast furnace at temperatures of about 2000'C.
C + O2 -> CO2
Then the carbon dioxide reacts with more oxygen to form carbon monoxide:
CO2 + O2 -> 2CO
Carbon monoxide goes on to actually react with the haematite ore:
3CO + Fe2O3 -> 2Fe + 3CO2
First the limestone (CaCO3) is decomposed to calcium monoxide and carbon dioxide:
CaCO3 > -> CaO + CO2
Then the calcium monoxide reacts with the silicon dioxide forming slag, which can be used for road-building or fertiliser:
CaCo + SiO2 -> CaSiO3