Iron Ore

Iron Ore is an early game ore, which spawns on the surface as well as in the Underground and Cavern biomes. Its primary use is to make Iron Bars, which can be used to make the Iron tier of equipment, as well as Buckets, Chains, and many other items. The equivalent of Iron Ore is Lead Ore, which will sometimes replace Iron in a world. Iron Ore also has a small chance to appear as a bonus drop from Slimes.

As Iron bars are needed to create an Iron Anvil, Iron Ore must usually be obtained before any weapons or armor can be created out of metal bars. This can be avoided by purchasing an Iron Anvil from the Merchant, but this is generally inefficient, as it is not difficult to find 15 Iron Ore early on in the game.

Trivia

 * Iron Ore and Lead Ore are the only ores that don't have corresponding bricks.
 * Real iron is very malleable and susceptible to corrosion, generally making it infeasible for crafting tools. The use of iron in Terraria more closely resembles real-life steel.

History
Eisenerz Minerai de Fer 철 광석 Iron Ore Железная руда 铁矿