Rock salt exists as ancient salt deposits and is often found deep underground in rock strata. Significant deposits exist in many parts of the world. Rock salt can be extracted as a dry salt using the classical underground mining technique of drilling and blasting. Since the late 1950s continuous miners or boring machines are in use. Depending on the purity of the salt, and the end use, upgrading the salt can be necessary. Different separation techniques are in use, i.e. manual sorting, sieving, optical sorting, electrostatic separation, and flotation. Since the salt is obtained in its dry form, and no evaporation step is involved, the carbon footprint of rock salt is relatively low.