Extracting salt from mines
Rock salt (halite) is the salt left behind by primordial oceans millions of years ago when lagoons dried out. These layers of salt were covered by rock formations and they are now located underground or inside mountains. Rock salt refers to the dry salt extracted from saliferous rock layers with the help of mining methods.
Most salt mines operate underground but in salt deserts the rock salt is also mined at the surface.
Two main methods of extracting rock salt are used in underground mining:
- Cut and blast mining consists in cutting slots at the base of the rock face. A series of carefully sited holes are drilled and then charged with explosives to blast the rock. The resulting salt rocks are then repeatedly crushed into pieces.
- Continuous mining produces smaller lumps of rock using a machine similar to the one used for building tunnels. It bores into the salt extracting lumps that are then crushed into smaller pieces.
Both methods ensure that the mine is stable and safe by leaving substantial pillars of salt to support the mine roof.
Rock salt represents 30% of the salt produced in Europe and the main producers are located in Germany and the United Kingdom.