Salt types and production

Rock salt

Rock salt deposits formed through the natural crystallisation of saline water in dry, hot conditions. Today, rock salt is extracted from underground mines or open quarries. Specialised machinery cuts the salt, which is transported to the surface and milled into crystals of different sizes. Coarser salt is mainly used for industrial purposes; finer grades are packaged for wholesale and used in the food industry. Rock salt is generally one of the less expensive types.

Naturally precipitated salt

This salt forms through natural evaporation in bodies of water such as salt lakes. Specialised machinery harvests the salt layer from dried lake beds. It is then milled, washed, dried and ground into coarse or fine particles. It contains more impurities; sodium chloride can account for around 95–96% of its mass, giving it a greyish appearance. Production is relatively inexpensive.

Vacuum-evaporated salt

Deep salt deposits can be worked by solution mining. Fresh water is pumped into the deposit to dissolve the salt, and the concentrated brine is brought to the surface through pipes. The brine is treated and evaporated under vacuum to obtain a purified product. In some processes, evaporation takes place in open basins using solar heat. Salt deposits can be very pure and require only limited additional purification. Vacuum evaporation produces salt with a high degree of chemical purity.