Back to Rocks and Minerals Articles
Hesham Najiya and Jason Cole
Salt, or sodium chloride, has been used by people well before recorded history. In ancient times, humans started realizing the importance of salt to their diet after they started cultivating their own farms and began relying less on wild game (which was the primary source of salt). Salt exploitation and use has interestingly shaped a major part of human history, possibly more than any other mineral. Even the word soldier, derived from the Roman word sal dare means "to give salt" because Roman soldiers were paid with salt as well as gold.
In its natural state, salt is normally found as the mineral halite, commonly called rock salt. Not surprisingly, the word halite is derived from the Greek word halos meaning "salt." Halite is usually found in and around salt springs, salt lakes, and in the ocean. It can also be found in salt domes, with are actually quite common in the Michigan Basin, and provide important traps for oil deposits. Some salt, or halite deposits are formed by the slow evaporation and eventual drying of enclosed bodies of salt water. Salt deposits can range from a few feet to thousands of feet in the Mediterranean basin. Other salt deposits are commonly found in sedimentary beds and in saline playa lake deposits such as the Great Salt Lake, Utah and Serles Lake, California. Salt is also recovered from seawater by evaporation. The cities of Cleveland and Detroit rest above huge halite deposits that are mined for road salt. In 1999, an estimated 209 million tons of salt were mined worldwide, with the largest producers being the United States (45 million tons), China (28.1 million tons), and Germany (15.7 million tons). Other major producers include Canada, Germany, India, Australia, Mexico, France, Brazil, and the United Kingdom.
In Canada, there are three major formations that are mined for their salt. It is estimated that Canada has over one million billion tones of halite in these formations. The three major salt formations are located in western Canada below the prairies, in Ontario, and to a lesser extent in eastern Canada.
Halite. Redmond Utah, USA. University of Waterloo Earth Sciences Museum Collection.
The human body is composed of 0.9% sodium chloride, and this salt is used for regulating blood volume and pressure including the flexibility of the blood vessels. Excess salt in the body (we only need about 500mg of salt per day) is associated with elevated blood pressure and heart problems. Because body salt is released during precipitation, athletes and those who sweat excessively are recommended to increase their salt intake.
Another primary use of salt is for clearing snow and ice off the roads during winter. Since salt has a lower freezing temperature than the surrounding ice, it is very effective at keeping our roads ice free. The fact that salt is also inexpensive, readily available, non-toxic, and easy to handle and spread, make it naturally the best candidate for the job. However, excess or careless salting of roads has proven to be harmful to the environment, harming low salt tolerant vegetation, and contaminating fresh water aquifers. Salt is also important in the production of industrial chemicals. Chemicals such as liquid sodium (used in coolants), chlorine, sodium carbonate (used in manufacturing glass), and hydrochloric acid are all important industrial chemicals produced from salt.
Common uses for salt
- Dietary
- Preserving Foods
- Industrial Chemicals
- De-icing roads and highways
- Water softener
- Fix and standardize dye batches in the textile industry
- Pulp and paper industry
The Wieliczka Salt Mine, Poland
The Wieliczka Salt Mine, located in southern Poland near the city of Krakow, has been worked as a source of rock salt since the late 13th century. The mine consists of over 200 km of underground passages, connecting more than 2000 excavation chambers on 9 underground levels extending down to 327m below the surface. Over the centuries, miners have established a tradition of carving sculptures out of the native rock salt. As a result, the mine contains entire underground churches, altars, bas-reliefs, and dozens of life-size or larger statues. It also houses an underground museum and has a number of special purpose chambers such as a sanatorium for people suffering from respiratory ailments. The largest of the chapels, the Chapel of the Blessed Kings, is located 101 meters below the surface; it is over 50 meters long, 15 meters wide, and 12 meters high. As a testament to its historical and artistic importance, the mine has been placed on UNESCO's World Heritage List of sites designated as having "outstanding universal value to mankind.'' It receives up to a million visitors yearly, most of them during the warmer summer months.
The India Salt tax
Indian history recalls the prominent role of salt, primarily its role in the British salt starvation policy. In 1780, salt manufacture in India was brought under government control, which at the time was British. The wholesale price was fixed at 2 rupees, of which 1.1-1.5 rupees went to the government as a tax. The farmers created sub-monopolies and the price of salt rose excessively. In 1788 a system of direct government auctions was started. This intended to break down any sub-monopoly, but subsequently had the opposite effect. Because of this system, that price of salt soared to as high as five rupees per maund (82 pounds) in some places, between the years of 1794 and 1874. Since the average wage per month for the commoner was between 1.1 and 1.5 rupees, no one could afford to buy salt. Many people died due to a lack of salt in their diets. Still, the British government refused to lower the price of salt. By 1930, at the time of Gandhi’s historic salt march, inflation had increased the monthly wage of a rural labourer in the Bombay Province to about 13.5 rupees and thanks to the salt march the Salt Tax had been reduced to 1 rupee a maund. This was only one step in Ghandi’s resistance to British rule.
Salt - inhabiting of North America
Salt has played a prominent role in American and Canadian history as well. When the major European fishing fleets discovered the Grand Banks of Newfoundland at the end of the 15th Century, the Portuguese and Spanish fleets used the "wet" method of salting their fish onboard, while the French and English fleets used the "dry" or "shore" salting method of drying their catch on racks. This preserved the fish for longer and allowed the French and British fishermen became the first European inhabitants of northern North America since the Vikings a half-century earlier.
Salt - the Ontario connection
The next few paragraphs are from a book called Picturesque Canada that was published by the Art Publishing company, in Toronto Ontario, during the year 1882 and was edited by Principal Grant. It discusses the origins of salt production in Ontario and refutes the claim that English salt was superior to Ontario salt.
"Goderich leaped into temporary importance a few years ago as the centre of a new industrial interest in Ontario. The Geological reports of Sir William Logan early announced that the Onondaga group of salt rocks of the Silurian series underlay the drift and limestones of a part of Western Ontario; but not till 1866 was salt actually discovered. At that time, people were boring for oil in almost every likely spot in the western part of the peninsula. At the depth of about one thousand feet, brine of the finest quality was found. Three beds, respectively of 19, 30, and 32 feet, were found, with slight intervals between, of pure crystalline salt, and others were subsequently reported of 60 and 80 feet in thickness. The new industry paid so well at first that everyone in Goderich invested in salt wells, nearly as eagerly as people a thousand miles away invest in the corner lots of paper towns in the north-west. The valley of the Maitland was soon covered with derricks, and the investors were happy. But good brine was discovered in other places, the Canadian demand proved too limited for the number of manufactures, and the United States market was "protected". Soon, most of the salt works had to be operated only partially or to close altogether. The confiding people who had invested their savings in them during the salt "boom", now gaze mournfully on the smokeless chimneys and buildings tumbling into ruin, that tell of wasted capital and effort. The story has a moral, but a new generation is not likely to learn it, for seemingly each new generation has to pay for its own experience.
The area of salt rocks has been found to stretch from Sarnia to Southampton, and east to a point beyond the prosperous town of Seaforth. There are salt deposits originating from an ancient landlocked lake, embracing a part of Michigan in the west, the Ontario Peninsula on the east, and stretching south as far as Syracuse in New York. The salt was solidified, under conditions hard for us to imagine, and in quantities sufficient to supply this continent for ages. As the salt rock is dissolved by the water that runs down the bore from springs, it follows that the older the well, the more abundant and constant will be the flow of brine, and that subterranean salt lakes will be formed of increasing extent and depth. At one of the mills, such an underground cavity lately swallowed up several hundred feet of iron tubing, and the rise in the level of the brine was such that seventy feet less of new tube sufficed to replace the old.
The chemical analysis of Dr. Sterry Hunt in 1866 indicated that the salt was the purest known, and the most concentrated possible. Subsequent tests, however, have shown a decided change, indicating an increase of gypsum and the soluble earthy chlorides of calcium and magnesium. This may arise from the brine acting as a solvent of the overlying earths, and increasing the impure elements. Chemical processes become, therefore, necessary to eliminate these foreign ingredients, and by this means the finest table salt , and salt of any quality for antiseptic or agricultural purposes, may be made. The brine is almost a saturated solution, having a density from thirty to fifty per cent, greater than any yet found in the United States. As yet the Chemical Company of Goderich is the only one that invokes the aid of chemistry; but science and new methods must come into play universally if we are to hold our own and develop our salt or any other industry. "Lack of finish" is frequently urged against Canadian products, and there is some ground for the charge, notwithstanding all that a short-sighted and miscalled patriotism may say. We may be quite sure that such an objection, if at all founded on fact, will be fatal in those days of fierce competition and nice adjustment of means to ends.
In 1880, an Ontario Agricultural Commission was appointed to inquire into the agricultural resources of the Province, and the commissioners found that salt now enters so largely into the business of the producer, especially as regards cheese and butter making, pork-packing, and the fertilizing of the soil, that its consideration could not well be ignored by them. They therefore made inquiries into its manufacture, the extent to which it is used, and the prejudices against Canadian salt and favour of English. The result of their inquiries was, that if properly manufactured and carefully dried, the well-known purity of Canadian salt is fully equalled by its adaptability to all dairying purposes, and its excellence as a factor in the work of fertilization. To show how extensively it is now being used in the west of the Province, it was stated that a Seaforth firm had in three months of the then current year sold 63,000 tons for fertilizing purposes. The evidence, with scarcely an exception, was also completely in favour of the use of salt as an agent in enriching the farm, promoting the growth, and protecting the early plant of the root crops against the ravages of the fly, and as a remedy for some of the enemies that assail the spring wheat crop. It is no small tribute to the purity of Canadian salt that, notwithstanding the high fiscal duty of the United States, it is used in immense quantities in the great American pork -packing centres. On the other hand, English salt is brought to Canada at little more than ballast rates, in vessels that come for freights of grain or lumber to Halifax, Quebec and Montreal. Of course this salt is admitted free of duty, and as it is used by the fishermen and the population generally of the Eastern part of the Dominion, the area over which Canadian salt can be profitably distributed is very much limited.