Lead Ore

Lead Ore is an early-game ore that generates on world creation on the surface, as well as in the Underground and Cavern layers. Its primary use is in crafting Lead Bars, which can then be used to craft the Lead tier of tools, weapons, and armor, as well as Buckets, Chains, and several other items. The equivalent of Lead Ore is Iron Ore, which will sometimes replace Lead in a world. Lead Ore has a small chance to appear as a bonus drop from Slimes.

As Lead Bars are required to craft a Lead Anvil, Lead Ore must usually be obtained before any tools, weapons, or armor can be crafted from bars. This can be avoided by purchasing an Iron Anvil from the Merchant, but it is usually easy to find the required 15 Lead Ores fairly early.

Trivia

 * Lead Ore and Iron Ore are the only Ores that don't have Bricks.
 * While Lead is used to craft equipment in Terraria, this would be highly implausible from a real world standpoint due to real being toxic, brittle, and very heavy.

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