Miner is the skill associated with both the mining labor and its associated profession. Miners are necessary to build any kind of fortress that is underground or involves stone. They are required to dig tunnels, channels, stairs and ramps, as well as remove said stairs and ramps. Miners require a pick to do any work.
Miners gain experience for every tile mined, which means they gain experience faster in easier-to-dig soil and slower in stone. Due to the constant demand, straightforward work and fast experience curve, miners level-up to legendary skill faster than any other profession. Most players will have one or two legendary miners within thirty minutes of gameplay.
Mining skill affects only the speed at which stone is mined, not the chance of acquiring resources from mining. Normal rocks and ore deposits drop an average of 1 boulder for every 4 squares mined; in compensation, one ore gives 4 bars of metal. Gem clusters drop rough gems 100% of the time.
In versions prior to v0.34.08, the rate at which mining drops stones is based on skill. If valuable gems or ores are being mined, it is best to use a Legendary miner for pre-v0.34.08 releases. Burrows can be used to restrict a certain mining expedition only to certain dwarves.
 Mining behavior
If a large area is designated for mining, miners tend to clear out the left side first, working from the top down as much as possible. This is not absolute but is a strong tendency.
Once mining, a dwarf will automatically continue on to mine any connected tiles (on the same level) designated for mining, even diagonally, rather than shift to mine a discontinuous tile.
Dwarves tend not to see tiles on different levels as "connected" (e.g. an up-stair below a down-stair), and will tend to clear one level before moving on to another - even to the point of moving far across a map to do so. They seem to mine top levels over lower ones.
If no mining-designated tile is connected they will seek to mine a top-left-designated tile on a top-most level.