Pick

From DwarfFortressWiki

A pick is a tool used by dwarves to mine areas you have designated for mining. Dwarves without picks cannot mine. Picks can be made from copper, bronze, bismuth bronze, iron, or steel. The material used only affects the weight of the pick and the damage it deals when used in combat; mining speed and product are not affected.

Miners can use picks as weapons using their mining skill. Only a dwarf who is set to fight "unarmed" and who is holding a pick at the time he or she is drafted will use it in combat. Picks are somewhat weaker than actual weapons like spears, but are still very effective in the hands of a skilled miner.