Have you ever wondered what salt is and where it comes from?   Did you know that salt is a rock?  While recently working on an experiment, that included salt, I wondered what it really is, so I did some research.

Salt is a clear brittle mineral that has been used to flavor and preserve food since ancient times.  Today, salt is also used in the manufacture of a large number of chemicals and chemical products.  It consists of the elements  sodium chloride and its formula is NaCL.  Its mineral name is Halite.

Salt usually forms clear  crystals that are almost perfect cubes.   However impurities in the salt may make it appear white, gray, yellow, or red.   Did you know that table salt appears to be white, but it actually consists of clear cubes?

The source of all salt, even deposits that are located underground, is called *Brine from seas, salt lakes, and similar bodies of water. Salt deposits that now lie underground where formed by the evaporation of seawater millions of years ago.

Uses of Salt
In the chemical industry, salt is mainly used to produce other chemicals.   Salt can be broken down and used to make a variety of sodium and chlorine products.  Salt is also used to make a chemical product called *soda or *soda ash which is used in the manufacture of glass and soap.

Did you know that when salt is mixed with ice , the melting point of ice is lowered?  well, as a result salt is often spread on roads and highways to melt snow and ice.

In the food industry, salt is used as a seasoning for food.  It is also used by food processing plants to preserve food.  Your body needs salt to stay healthy.   Human blood contains of salt, and body cells must have salt to function properly.   Studies have proved that too much salt in a persons diet can lead to high blood pressure.

Where Salt Comes From
Salt comes from two main sources.   Seawater, salt from the sea, is salty because rain water dissolves minerals containing sodium and chlorine in rocks and soil.  Rivers and creeks are important because they carry these minerals to the sea.  Evaporating seawater is the oldest method of obtaining salt and it is often called solar salt.  Solar saltworks require a hot, dry climate to speed up the evaporation process.

The other main source of salt occurs in hard massive layers beneath the ground.   This is called rock salt which is formed by the evaporation of large parts of oceans millions of years ago.  Underground salt deposits are found on every continent.  In the U.S.A. these deposits occur in 32 states.

There are two basic methods for removing salt from the ground.  One method is called room-and-pillar mining.  In room-and-pillar mining, shafts are sunk into the ground, and miners break up the rock salt with drills.  The miners remove chunks of salt, creating huge rooms that are separated by pillars of salt.  This method requires that about half the salt be left behind as pillars.

The other method is called solution mining.  In solution mining, a well is drilled into the ground, and two pipes are lowered into the hole.  These pipes consist of a small central pipe inside a larger pipe.  Fresh water is pumped down the central pipe to the salt deposit.  The water dissolves some salt to brine.  The brine is then pumped to the surface through the outer pipe.

How Table Salt Is Made
After salt has been collected by mining or evaporation, it is sorted for quality and then crushed, ground, and screened into batches according to particle size.  High quality salt that has been ground into fine particles is used as table salt.  This fine grain salt tends to cake at high humidities, so manufacturers add a free-flowing agent to it before packaging.

Much of the table salt purchases by consumers is also *iodized.  A lack of iodine in a person's diet can result in a condition called goiter, in which the thyroid gland becomes enlarged.  A small amount of iodine is enough to prevent goiter.

Salt Facts
1. The early Chinese used coins made of salt for currency.

2. The need to transport salt from Syracuse was one of the main reasons for the construction of the Erie Canal, completed in 1825.

3. Production of salt from underground mines began in the the mid-1800's.   Drilling helped revolutionize knowledge of the earth's layers.