Rock salt deposits can also be mined via solution mining, Water is pumped down a borehole, dissolving the salt. The salt-laden brine is pumped back to the surface for processing. In some cases, especially in the chemical industry, the brine is used as such, without prior drying of the salt. For use in the chemical industry, calcium, magnesium and sulphate have to be precipitated from the brine. The empty boreholes can represent an important source of revenues for the solution miner, as they can be used as caverns for the storage of gas or hydrocarbons.