You may have heard the expression, “salt of the earth” and wondered why that image should apply to virtuous people. After all, today we consider it a virtue to cut back on salts in our diets.
Salt in Scriptures
The expression “salt of the earth” has a Biblical pedigree, specifically Matthew 5:13, a text that makes up the Sermon on the Mount. The verse opens: “You are the salt of the earth.” It then continues with a warning that salt that loses its savour, flavor, or saltiness -- depending on your choice of translation -- becomes useless, and so would be thrown out and trampled on.
It’s an interesting question to consider why salt is offered as the symbol of this quality of a person.
Idiomsonline offers the suggestion that “earth” here does not refer to the ground or the planet but to something else made of earth in clay form, namely in the oven. It explains as follows:
"In Israel, salt has a high concentration of magnesium and blocks of salt were used as catalysts for fires in ovens. This explains Jesus question about salt losing its savour. Salt does not lose its salty flavor, but as the salt lost its magnesium it lost its ability to stoke fires. Jesus was saying “once salt loses its ability to burn it is no longer good for anything but to be spread on roads.”
As proof, it offers another New Testament verse on salt: Mark 9:49-50:
“For every one shall be salted with fire, and every sacrifice shall be salted with salt. Salt is good: but if the salt have lost his saltness, wherewith will ye season it? Have salt in yourselves, and have peace one with another.”
It’s possible that Leonardo da Vinci had this in mind in depicting an overturned salt cellar next to Judas in his famous Last Supper. Some take the overturned salt as a symbol of betrayal, though Morton Salt’s Salt History also sees in it the origin of the association of “bad luck” with spilled salt, a superstitious belief that persists.
Civilization and salt
Salt was prized in the ancient world for its utility, particularly as the primary preservative for meat, as well as a flavor-booster. It also made it possible to preserve dairy products in the form of butter and cheese that could be safely stored for far longer than milk could in the absence of refrigeration.
Morton’s Salt History sees an even more central role for salt in civilization. It suggests that salt itself dictated where societies settled. It suggests that people who sought meat and salt for their own consumption followed animal trails to salt licks. “Their trails became roads and beside the roads; settlements grew.” That formed the basis for a village or even a state.
In some of these states, salt came to be used as a form of currency. Saltworks recounts, “The expression ‘not worth his salt’ stems from the practice of trading slaves for salt in ancient Greece.” It also is considered the root of our word for pay, “salary,” which is derived from the Latin “salarium agentum,” the term applied to the salt allotted to soldier of ancient Rome."
Salt of the sea
Of course, people who settled near oceans had access to as much salt as they wanted from the saltwater once they figured out a method of extracting the salt crystals. In warm climates, that was easily done with solar evaporation.
Morton’s Salt Production and Processing identifies solar evaporation as the oldest method of obtaining sea salt. All it entailed was “capturing of salt water in shallow ponds where the sun evaporates most of the water.” What’s left behind is “concentrated brine” from which the salt is extracted.
You can see that sea salt process illustrated in this video, which also celebrates the more flavorful product of the process:
A newer method of extracting salt from the sea is called the Vacuum Evaporation Method. It involves some more advanced engineering, that entails two-steps: one is solution mining, and the other is pumping the brine through vacuum pans. Morton explains the process this way:
Wells are drilled from several hundred to 1,000 feet apart into the salt deposit. These wells are connected via lateral drilling, a recently developed technology. Once the wells are connected, the solution mining operation begins: water is pumped down one well, the salt below is dissolved, and the resulting brine is forced to the surface through the other well. It is then piped into large tanks for storage.
After that, they pump the brine nearly 45 feet high “closed vessels under vacuum” that are set up in small groups “with each one in the line under greater vacuum than the preceding one.” As it progresses through the different vessels with greater vacuum, the pressure is reduced.
The idea is that lowering pressure allows water to boil at a lower temperature, so they don’t need to heat the water all the way to 212° Fahrenheit (100 degrees Celsius) to achieve evaporation. ”Vacuum pans may operate at as low as 100°F.”
While Morton’s insists that all impurities are removed from the salt, Healthline warns that some may remain behind, especially if the saltwater source was polluted. The additions aren’t necessarily harmful, as there may be “trace minerals like potassium, iron, and zinc,” though not in large enough amount to be considered a real health benefit.
Sea salt crystals are larger than standard table salt, and that is part of the reason it is preferred by some to deliver great impact upon taste when it is sprinkled over food.
Getting salt out of the earth
Above is a video of the world's largest salt mine. It's in Canada.
Rock Salt Mining is the second oldest method of salt production Morton identifies. Just like other mines, salt mines are underground with the sought-after mineral in veins or in salt domes found deep in the bedrock.
The method used for mining is called “the room and pillar method.” That involves removing about half the salt “in a checkerboard pattern to leave permanent, solid salt pillars for mine roof support.”
As in metal mining, explosives are used to blast out rock salt. That can bring hundreds or even thousands of tons of rock salt out. That is then brought to the surface where it is screened and sorted into different sizes then shipped out on actual boats or trains or trucks.
This short video illustrates the methods used in salt mining today:
Among the salts extracted from mines is Himalayan Pink Salt, which, according to Healthline gains its distinctive hue from the amounts of minerals, particularly iron. It is estimated to “contain up to 84 different minerals and trace elements.”
The source of the salt is the Khewra Salt Mine, among the most venerable and substantial salt mines on the planet. It is supposed that the salt there is the product of water that dates back millions of years.
Here's a video of the Khewra Salt Mine.
Unlike the processes typically used in mining, Himalayan pink salt is said to be “hand-extracted and minimally processed to yield an unrefined product that's free of additives and thought to be much more natural than table salt,” Healthline reports.
The pink crystals are not limited to food uses, Healthline adds. One popular use is as bath salts that are said to be soothing and to ameliorate skin.
The pink salt could also be made in salt lamps that are associated with improving air. They also are used for purposefully formed salt caves that are said to improve breathing and skin conditions, though that effect is not borne out by scientific studies.
A promotion for salt caves for therapeutic effects can be seen below:
What you have in your salt shaker is likely standard table salt, which is mined rock salt ground up finely. If you look at the container it came in, it will either let you know that the salt contains iodine, a nutrient that has to be added, or it will warn you that it does not contain it.
Iodine is added to salt in the form of potassium iodide as a supplement for good health. As Healthline explains, Iodine deficiency is a leading cause of hypothyroidism, intellectual disability, and various other health problems.
You may have noticed some recipes call for “kosher salt” and wondered what makes salt kosher or not. The fact is that all salts are kosher. The difference is the salt with that label is the type of salt that is used in the koshering process of extracting blood from meat or poultry.
This type of salt is more coarsely ground than table salt, which is why it is preferred for some dishes. It also would not contain iodine or any anti-caking agents sometimes included in the more finely ground salt. So it may be purer as far as salt goes, but that is not the reason for its “kosher” label.
Given the different shapes, you get more salt per spoonful for standard table salt than you do for kosher salt, so you can't merely substitute one for the other. This video explains the need for adjustment between the two: