Iron is the fourth most common metal element in the earth's crust and forms the basis for much modern industry. Iron is also a common element among the bodies of the solar system, including the Sun, planets and meteors. The atomic weight of iron is 55.847, and its atomic number is 26. Its atomic symbol is Fe, from the Latin word ferrum. It has a melting point of 2800.4°F (1538°C) and a boiling point of 5181.8°F (2861°C).

Iron occurs naturally in combination with oxygen in the ores hematite, limonite and magnetite. These have about a fifty percent iron content. Since high-grade ores such as these have slowly been depleted, the use of lower-grade ores like taconite, (with twenty to forty percent iron content) has increased. In addition, recycled iron and steel has become essential in steel production.

As a metal, iron has been in use since...