Dirt Block

Dirt Blocks are one of the most common block types in the game, covering a huge chunk of the world's surface. They are almost surely the most visible and accessible block to new players, which makes them useful for building a rudimentary shelter to take refuge in during a player's first night. These blocks may be covered by grass, corruption or hallow (upon engaging hardmode), which spread from adjacent dirt blocks. It can be moved around freely with a Dirt Rod.

Location
Natural caverns close to the surface are largely made of dirt. When the Underground starts, the caverns are made of roughly 50% of dirt. To the point below where the sand is generated, small amounts of dirt is generated which lasts until the bottom of the Cavern.

Properties
Dirt blocks are one of the most fragile blocks in the game. A single hit from most Pickaxes will successfully mine them, but dirt blocks with any kind of grass on them may take two hits.

NPCs won't accept a house made with naturally occurring dirt walls. The background walls must be crafted and placed by the player to be considered safe for habitation. Player placed dirt walls have different data values than the generated dirt wall, but still merge with the natural dirt wall.

After the Wall of Flesh has been defeated on a world, corruption will spread through Mud Blocks. When it does, it "dries" them, converting them automatically to Dirt Blocks. As a result, mud may become more rare in worlds that have entered hardmode. Players can "moisten" dirt once again to produce mud, if needed.

History
Bloc de terre Земляной блок