A Mattock is a useful digging tool that also makes a decent weapon.
It can be bought in certain shops or occasionally found in crates. It is also guaranteed to be found at the bottom of a snake pit, buried beneath the two rubies.
The difference between a mattock and a pickaxe is that mattocks have a flattened adze instead of a chisel head, making it more effective at digging through dirt and chopping wood.
The Mattock is used for digging through blocks, either to create a passage or excavate treasure. It can also be used as a melee weapon against enemies.
Unlike the whip, mattocks must be carried in the hands, so they must be dropped to carry items such as Golden Idols.
If there is a block in front of you that can be dug through, you can hit the block with the 'action' key (default X) and it will be destroyed. If there is no tile directly in front of you, it will instead dig through the block below the space in front of you.
The mattock can dig through any solid block, but it cannot dig through non-solid blocks (such as webs and ladders), the level border, or the Moai.
Mattocks have a limited durability before they break, dropping a Mattock Head. Each mattock is different, and in true Spelunky style, the number of uses is random.
Each time the mattock is used (hitting an enemy or destroying a block), there's a 5% chance the Mattock will break. This means that on average, a mattock will last for 20 strikes.
However, this calculated average is distorted upward by the realistic possibility that a mattock will last for a very long time.
The Tunnel Man
When the Tunnel Man is unlocked as a player character, he uses a mattock as his main weapon instead of the whip used by The Spelunker and the Damsel.
As a professional, he knows how to take proper care of his tools. As a result, his weapon (and any other mattocks he picks up) will never break, however much they are used.