Nature Bulletin No. 340-A April 12, 1969
Forest Preserve District of Cook County
George W. Dunne, President
Roland F. Eisenbeis, Supt. of Conservation
It is fortunate that Salt -- common salt, known to chemists as sodium
chloride and to mineralogists as Halite -- is one of the most abundant
substances on earth, because most of us crave it and must have it.
Eskimos get along without salt because they live mostly on the
uncooked flesh of fish and mammals. A few nomad tribes never eat it
and do not need it because their diet contains so much milk cheese,
and meat eaten raw or roasted. We people who eat boiled meat and
many vegetables must have salt.
Of the millions of tons produced commercially each year, only about
three percent is used as table salt. Large quantities are required for
refrigeration meat packing, curing and preserving fish, pickles,
sauerkraut, and for other foods prepared in brine. A lot of it is needed
for livestock. Salt is spread on sidewalks, streets and highways to melt
ice in winter. It is used to glaze pottery, sewer pipe and other ceramics.
It is required in many metallurgical processes, chemical industries,
and the manufacture of such products as leather, glass, soap, bleaching
powder and photographic supplies. It has about 14,000 uses.
Salt has always been one of the most important articles of commerce
because in many regions it was difficult to obtain. In old China, it was
second only to gold in value; in Tibet, salt cakes with the stamp of the
Great Khan were used as money; in Africa, slaves were sold for cakes
of salt carried to remote tribes. The caravan trade of the Sahara Desert
is largely in salt, and the Via Salaria, one of the oldest roads in Italy,
was the route over which this prized commodity was transported. Our
word "salary" and the expression "not worth his salt" are derived from
salarium, an allowance given the Roman soldiers to buy salt Included
in the tax levied by Montezuma on each city in Mexico were 2000
loaves of pure white salt for himself and the nobility. A tax on salt,
with heavy penalties including death for anyone found making it from
sea water, helped bring about the French Revolution. In America,
many wars were fought among the Indians, and against them by the
whites, for possession of salt springs and salt licks to which deep trails
were worn by animals The pioneers made long dangerous trips to get
salt, and it was worth from $10 to as high as $64 per barrel in some
Salt is obtained from ocean water which contains about one-quarter
pound per gallon; from inland seas with no outlet, such as Great Salt
Lake in Utah -- which is several times as salty as the ocean -- and the
Dead Sea in Palestine; from natural brines in underground rock layers;
and from almost inexhaustible beds of Halite, or rock salt. In this
mineral form it is usually transparent or white but may be colored
yellow, red, brown, blue or even purple by impurities. The crystals are
almost invariably cubes, as you may see by examining the tiny grains
of table salt.
At St. Claire, Michigan, there are four beds of rock salt varying from
21 to 318 feet in thickness, separated by layers of shale and limestone,
at depths from 1630 to 2431 feet below the surface. There they drill a
hole and pump down water which dissolves the salt and forces the
brine to the top. Salt is also mined. Far beneath Detroit there is
another city, a salt city, with huge trucks and jeeps with trailers
traveling over its glittering streets. In the Carpathian mountains of
Poland, 1000 feet down, there is a salt mine with 65 miles of galleries
and 30 miles of railroad. Britain, Russia, Germany, France, India and
China are other salt producing countries but the United States is the
greatest, led by Michigan.
You can take that yarn about Lot's wife with a grain of salt.
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Update: June 2012