Colorless or white; also blue, purple, red, pink, yellow, orange, or gray
Halite, commonly known as table salt or rock salt, is composed of sodium chloride (NaCl). It is essential for life of humans and animals. Salt is used in food preparation across the globe.
Rock Salt Mining:
Many rock salt mines use the room-and-pillar method of underground mining in which the resource is extracted, leaving ‘pillars’ of the material untouched, which creates ‘rooms.’
Solution mining involves injecting a solvent to dissolve and recover underground soluble salt minerals. The saturated brine is pumped to the surface for recovery via solar evaporation and further processing.
Seawater is collected and allowed to evaporate in specially constructed concentration and evaporation ponds. The initial step concentrates the brine to raise the salinity and to allow various calcium, magnesium, and iron compounds to precipitate from solution. The brine circulates among a network of interconnecting gravity-fed ponds, with salinity increasing with each transfer. It takes approximately 2 to 5 years from the time seawater is initially introduced before the first salt is ready for harvest.
Inland Solar Evaporation:
The principles of solar salt concentration and production are similar to those along coastal margins except that salinity of inland lakes usually is greater than that of seawater and a yearly crop of salt can be harvested. As water flows over or beneath the surface, it dissolves minerals from underlying soils and rocks. The salt lakes are topographically lower than most of the surrounding areas and, therefore, become excellent sumps for mineral accumulation.
Over 40% of salt is used in the chemical industry (mainly for the preparation of sodium hydroxide, soda ash, hydrochloric acid, chlorine and metallic sodium) and another 40% as a de-icer on roads in winter. The remaining is consumed in several sectors, including manufacture of rubber and other goods, agriculture, and food processing including table salt.