For some purposes rock salt may be used in its solid, raw form, but all other salt undergoes some purification process. From rock salt. Salt domes and beds of rock salt that lie on or near the surface can be excavated in much the same manner as any other mineral deposit. If the salt is of sufficiently high quality, it may simply be ground, sieved, and sold. If impurities are present in unacceptable levels the rock salt may be dissolved to form a brine.
Commercial salt is manufactured by treatment of the brine, as described below.
Where salt deposits are too far below the surface to be mined efficiently, water may be pumped down to dissolve the deposits. The resultant brine is then collected and treated. China, Facts about From seawater and brines. Seawater and brines are processed by solar evaporation wherever possible. The brine is channeled through a series of shallow ponds where it becomes increasingly concentrated.