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. 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. The cities of Cleveland and Detroit rest above huge halite deposits that are mined for road salt. These deposits are mined by drilling wells into the salt layer, and pumping hot water to quickly dissolve the salt. When the water becomes saturated with dissolved salt the solution is known as "brine" , it is pumped out.
When the brine evaporates, the remainder is primarily sodium chloride, which is refined and utilized. Inland lakes that are rich in salt exist in many arid regions, especially in the desert Southwest. In such lakes there is more water being evaporated than the amount entering, causing the volume of water to decrease, while increasing its salinity.
In some lakes, concentrations of salt brine can become so extreme that a stick or stone placed in the water will become coated with a layer of halite. As the water evaporates, the shoreline recedes and chunks of salt are left crystallized on the beaches.
Many of these inland lakes have already dried up completely, leaving enormous salt deposits that are commercially mined, as at Searles Lake, California in the Mohave Desert. Well crystallized specimens of halite cubes are very impressive and quite popular with rockhounds. Halite crystals form so fast and so well in some evaporative lakes that many such specimens that are sold worldwide in rock shops and at mineral shows were grown within the past year.
Some halite crystals are colored pinkish by bacterial debris trapped during crystallization while others are colored bright purple or blue, with a silky luster.
Physical Properties of Halite Chemical Classification Halide Color Colorless or white when pure; impurities produce any color but usually yellow, gray, black, brown, red Streak White Luster Vitreous Diaphaneity Transparent to translucent Cleavage Perfect, cubic, three directions at right angles Mohs Hardness 2. Some minerals are toxic or contaminated by other people tasting them.
Chemical Composition NaCl Crystal System Isometric Uses Winter road treatment, a source of sodium and chlorine for chemical processes, food preservation, seasoning. Find Other Topics on Geology. Maps Volcanoes World Maps. Colorless or white when pure; impurities produce any color but usually yellow, gray, black, brown, red. Mohs Hardness. Cleavage, solubility, salty taste The taste test is discouraged.
Winter road treatment, a source of sodium and chlorine for chemical processes, food preservation, seasoning. Rock and Mineral Kits. Are Water and Ice Minerals? Mohs Hardness Scale.
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