Rock salt is called halite, the natural form of salt, is a very common and well-known mineral. It is found in solid masses, and as a dissolved solution in the oceans and in salt lakes. The inland lakes that are rich in salt exist in arid regions, and may also be below sea level without an outlet. These lakes evaporate during dry seasons, causing a recession in the water level and an increase of salinity content.
Underground mining is the second oldest method of producing salt. This is probably the most dramatic method of gathering salt. Rock salt mining production equipment is used to load and haul the salt to machines that crush and feed the salt onto a conveyor belt. The lumps are conveyed to a series of stations for crushing and additional sizing of the lumps. The salt is then placed in a storage bin to await hoisting to the surface.
The above ground processing of the rock salt consists of screening the mined salt into various marketable sizes by sorting through mechanically operated screens. When separated, each size is conveyed to its individual storage bin to await packaging for shipment or to be loaded as bulk salt into railroad cars, trucks, river barges or lake boats for shipment to customers.
In Nigeria, rock salt is mined using underground mining, the main equipment including: jaw crusher, cone crusher, and mobile crushing station.