Glossary

Iron is a metallic element with the chemical symbol Fe (from the Latin ferrum) and atomic number 26. It is one of the most abundant elements on Earth—making up about 5% of the Earth's crust—and is the primary component of the planet’s core. Iron is the foundation of modern industry and metallurgy, serving as the base metal for steel, which is the most widely used material in the world.

In its pure form, iron is a lustrous, silvery-gray metal that is relatively soft and ductile. However, pure iron is rarely used in practice because it corrodes easily when exposed to moisture and oxygen, forming iron oxide (rust). Instead, iron is almost always used in alloy form, where it’s combined with small amounts of other elements such as carbon, chromium, nickel, or molybdenum to improve its strength, hardness, and corrosion resistance.

Iron’s versatility comes from its ability to exist in several crystalline forms (allotropes) and to combine easily with other elements. When carbon is added in controlled amounts (typically 0.02–2.1%), it becomes steel, which can be hardened, tempered, and alloyed for countless industrial applications. Higher carbon content (above 2%) produces cast iron, which is harder but more brittle.

Most of the world’s iron is extracted from iron ore, primarily from minerals like hematite (Fe₂O₃) and magnetite (Fe₃O₄). The extraction process involves smelting, where the ore is heated in a blast furnace with coke (carbon) and limestone. This chemical reduction removes oxygen from the ore, producing molten pig iron, which is then refined into steel or other iron-based alloys.

Iron’s unique combination of strength, magnetism, and abundance makes it indispensable across nearly every industry. It’s used in construction (beams, rebar, bridges, ships), machinery, automobiles, tools, pipelines, and fasteners. It also plays a vital biological role—iron atoms in hemoglobin enable red blood cells to carry oxygen throughout the body.