Salt Shaped Empires: Mapping Deposits of the World's Most Powerful Mineral
- Oliver Thamm
- May 29
- 34 min read
Updated: Jun 14
40 mins
This is Civilization Explained, and I am your host, Oliver Thamm. In this series, we look at geo-data first and explore world history from that perspective. And today is all about: Salt.
PRODUCT MENTIONS
The official tee "The Salt of the Earth" of the episode for your special loved ones.
Table of Contents
Appendix:
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The Chemistry of Salt: More Than Just Table Seasoning
When you hear the word salt, chances are you picture the white shaker next to the pepper mill. But in chemistry, "salt" refers to a whole group of compounds formed when an acid reacts with a base. These salts are everywhere—in our food, in our homes, on our roads, and even inside our phones.
Let’s start with the celebrity of the salt world: sodium chloride (NaCl)—a.k.a. table salt. It’s what makes fries taste great and pickles stay fresh. About 90% of the salt we mine or harvest from the sea is this one compound. On a chemical level, it’s just sodium and chloride ions arranged in a neat crystal structure. Simple, but incredibly useful.
But when salt is pulled straight from nature—whether from deep underground mines or sun-baked salt flats—it doesn’t come out pure. It brings along other minerals that can reveal clues about where it came from.
Take magnesium chloride (MgCl₂), for example. It’s often found in sea salt and gives it a slightly bitter taste. But it’s not just a flavor note—magnesium is used to make lightweight metal parts for airplanes, cars, and electronics. That trace in your salt could be a leftover from ancient oceans or long-vanished lakes.
Another tagalong is potassium chloride (KCl), sometimes called potash. If you’ve ever used fertilizer, chances are you've handled this salt. Plants love potassium—it’s one of the big three nutrients (along with nitrogen and phosphorus) that help things grow. So yes, some salt can help your tomatoes thrive.
And this is just scratching the surface. The salt family includes a bunch of compounds with some pretty surprising jobs:
Baking soda (sodium bicarbonate) is a salt. It makes your cookies rise by releasing bubbles when heated.
Washing soda (sodium carbonate) helps clean your clothes and softens hard water.
Calcium chloride (CaCl₂) melts ice on winter roads and stabilizes gravel during construction.
Copper sulfate (CuSO₄) is that bright blue stuff used to fight mold and pests in vineyards and farms.
Magnesium sulfate (MgSO₄)—better known as Epsom salt—is what you soak in after a long day.
Potassium nitrate (KNO₃), or saltpeter, was once packed into muskets and cannons as a key part of gunpowder.
Lithium carbonate (Li₂CO₃) plays a big role in modern tech—it's used in lithium-ion batteries that power phones, laptops, and electric cars.
So the next time you reach for the salt shaker, remember: you're not just seasoning your food—you’re holding a member of a fascinating chemical family that's helped build civilizations, grow food, fuel battles, and power the digital world.
From Grit to Greatness: How Table Salt Gets Purified
Before salt ever lands in that neat little shaker on your table, it usually starts out looking a lot less appetizing. Picture a crusty chunk of ancient ocean, dug out of the ground, packed with not just sodium chloride but also a bunch of tagalongs—like calcium, magnesium, iron, and maybe even a little clay or algae for good measure. To turn that messy mix into the clean, snow-white crystals we know and love, people have come up with some pretty clever tricks over the centuries.
Some of these methods sound like straight-up alchemy. Others? More like kitchen science. Let’s break it down.
Step One: Dissolve and Filter
Believe it or not, the first step to cleaning salt is getting it wet again. Raw salt is dumped into large tanks of warm water to make a super-salty solution called brine. The cool part? Sodium chloride dissolves easily—but a lot of the junk doesn’t. Think of it like brewing tea but leaving the sticks and stems behind.
Next, the brine is filtered. Sometimes it runs through massive industrial filters. Other times, it’s left to sit in big tanks so the heavy stuff (like sand or clay) can slowly settle at the bottom, like a salty snow globe.
Step Two: Additives That Act Like Bouncers
Now, some impurities are still floating around—especially dissolved minerals like magnesium and calcium. So, here’s where a little chemical help comes in.
Washing soda (sodium carbonate) is often added. It reacts with unwanted minerals and turns them into solids that are easier to remove. (Yep, it’s the same stuff used in laundry boosters.)
Lime (calcium hydroxide) helps kick out magnesium by turning it into magnesium hydroxide, which clumps up and sinks.
Sometimes, lye (sodium hydroxide) joins the mix. It boosts the pH and helps even more impurities drop out. And yes—this is the same lye used in making pretzels glossy or curing olives.
Some traditional methods are even more creative. In Zigong, China, where the brine has a bitter magnesium bite, salt workers added crushed yellow soybeans during boiling. The proteins in the beans helped bind up the bad stuff, which floated to the surface and could be skimmed off like foam.
In Hawaii, black lava salt is made by mixing in activated charcoal and volcanic soil. This not only adds minerals but gives it that dramatic black color and a detox marketing boost.
Once the chemical reactions are done, the solid gunk either settles naturally or gets filtered out.
Step Three: Evaporate and Crystallize
With the brine cleaned up, it’s time to get rid of the water and leave only pure salt behind.
Traditionally, this was done using pottery or iron pans. In some places—like the Philippines—salt is still made in small batches using traditional briquetage vessels, shaped into "dinosaur egg" salt balls. In other regions, large iron pans came into use, lasting for years of repeated boiling.
Today, high-tech factories use vacuum evaporation. By lowering the pressure, they can make water boil at a lower temperature—so salt crystals form more gently and evenly. It’s like slow-cooking a pot of brine until gleaming white crystals fall out of solution.
What’s left is over 99% pure sodium chloride, dried and sorted by size. A little anti-caking agent is often added so it doesn’t clump in humid kitchens. Sometimes iodine is added too, to help prevent iodine deficiency.
And just like that—after a journey through water, chemistry, and a bit of heat—you’ve got table salt: clean, crisp, and ready for your fries.
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Salt and the Human Body: More Than Just Flavor
Salt has been prized for centuries—not just for making food taste better, but for keeping it from going bad. Before refrigerators were even a dream, salt was a miracle worker. It kept fish from rotting, preserved meats like salt pork, and helped turn cabbage into long-lasting sauerkraut. Olives in brine? Also salt's doing.
How? Salt draws water out of food, and with less water, bacteria have a much harder time surviving. That made salt essential for both everyday meals and emergency stockpiles, whether it was a family pantry or an entire community’s food reserves.
But salt isn’t just good for preserving food—it’s critical for preserving you.
Your Body Runs on Salt (Literally)
The human body contains about 250 grams of salt—roughly a cup’s worth. And we lose it all the time: through sweat, tears, and even just breathing. To keep things running smoothly, we need to take in 1 to 5 grams of salt every day.
That’s because salt contains sodium, a key electrolyte. Sodium helps regulate fluid balance, nerve signals, and muscle function. In other words, it keeps your heart beating, your brain thinking, and your body moving.
When you don’t get enough salt—especially if you’ve been sweating a lot—you might feel tired, dizzy, nauseous, or just downright foggy. Severe salt deficiency can lead to confusion, headaches, muscle cramps, and worse.
But… Too Much of a Good Thing?
Here’s the catch: while some salt is essential, too much can lead to health problems. High salt intake is linked to high blood pressure, heart disease, and kidney issues. It’s all about balance.
Foods like meat, fish, eggs, and dairy already contain some natural salt. But vegetables, grains, and staple crops don’t. So if your diet leans plant-based, you’ll need to add a bit of salt to stay healthy.
Supplements: What Else Do You Need?
Salt isn’t just for seasoning—it’s also a global delivery system for life-saving nutrients. Over the last century, governments around the world have used salt to fight some of the most common and preventable health problems, all by adding a few key supplements to your daily pinch.
Iodine: The Cure for Goiter and Cretinism
In the 19th century, Swiss doctors made a critical discovery. People living in mountain regions like the Alps and Himalayas were suffering from swollen thyroids—known as goiters—and, in severe cases, developmental disorders such as cretinism. The culprit? A lack of iodine, a mineral essential for proper thyroid function. In high-altitude areas, glacial runoff had stripped iodine from the soil, leaving local diets deficient.
The solution was brilliantly simple. These physicians persuaded lawmakers to add iodine to salt, which was already a universal part of the diet. The result? Goiter rates plummeted, and iodine deficiency nearly disappeared in affected regions. Today, iodized salt is used worldwide to prevent these once-common disorders.
Fluoride and Folate: Expanding the Formula
The success of iodine opened the door to other public health interventions. Fluoride was added next—primarily in water, but also in salt in some countries—to combat tooth decay, especially in areas with low natural fluoride levels. The impact has been dramatic, contributing to major reductions in childhood cavities.
Later, many countries began fortifying staple foods and sometimes salt with folic acid, a synthetic form of folate (vitamin B9). This step was taken to prevent neural tube defects in newborns—a condition that occurs early in pregnancy if the mother’s folate levels are too low.
Ancient Salt Markets: Private and Industrial Consumption
Throughout history in times of peace and undisturbed trade, table salt was cheap and easy to find in most markets. For example, in the Roman Empire, a kilogram of salt cost about 1/6 of a worker’s daily wage, and a typical household used around 50 kilograms per year.
Private demand was continuous and fairly high volume. At the same time an individual purchase of a week's or even month's supply was still transportable by a single person. This made salt a popular substitute for currency in many regions of the world.
Even the lower-grade salt—the stuff not pure enough for your table—was in high demand. Why?
Livestock: Cattle, sheep, and other animals need salt too—about five times more than humans. Without it, herds would weaken or wander in search of salty soil.
Leatherwork: Salt was key to “pickling” animal hides before they were turned into leather. It kept the skins from rotting and made them easier to tan.
Metalworking: Salt served as a flux, helping purify ores and lower the melting point of metals. In other words, it helped ancient blacksmiths do their thing.
Military logistics: Salt kept food from spoiling during long campaigns. It was in salted fish, game, and meat, olives in brine, and army bread. Moreover, food foraged in hostile territory also needed preservation. Without salt, supply chains would break down fast.
Salt even had spiritual significance. It featured in religious rituals across Greek, Hebrew, and Roman cultures. The Bible famously tells of Lot’s wife, who was turned into a pillar of salt, and Jesus called his followers the “salt of the earth”. It is recurring pattern even today. For example, native Hawaiians believe that alaea salt has spiritual power; it is used in traditional ceremonies, for ritual blessings and purifying, and for healing purposes.
No surprise then: keeping a steady supply of salt was a strategic priority, almost like having access to oil or gas today. Losing your salt supply could mean economic collapse, sick animals, a weakened military, and spoiled food—all in one blow.
Fast Forward: Salt in the Modern World
These days, salt still plays a massive role beyond the dinner table—and in more ways than the ancients could’ve imagined.
Today’s industrial uses of salt include:
De-icing roads in winter with rock salt or calcium chloride—keeping traffic moving and accidents down.
Water treatment systems use salt-based resins to soften hard water and remove impurities.
Chemical manufacturing relies on salt to make products like PVC, bleach, and caustic soda.
In oil and gas drilling, salt solutions are used in drilling fluids to cool equipment and stabilize boreholes.
Food processing still leans on salt—not just for flavor, but for preserving snacks, curing meats, and even fermenting cheese and pickles.
And then there’s medicine and health—from saline IV drips to electrolyte solutions and salt-based tablets.
And let’s not forget the tech world: salts like lithium carbonate are key ingredients in rechargeable batteries that power phones, laptops, and electric cars.
From sacred rituals and military rations to high-tech batteries and road safety, salt is far more than just a kitchen staple. It’s been a silent force behind human progress for thousands of years—and it’s still hard at work today.
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How the Sun Makes Salt: The Craft behind Sea Salt Pans
Long before salt came in tidy cardboard boxes, people were harvesting it straight from the sea—with nothing more than sunshine, seawater, and a bit of engineering know-how.
Back in the day, in places all around the world, locals figured out a smart way to trap the sea and turn it into salt. Using dykes and floodgates, they controlled the flow of seawater into shallow lagoons. These ponds, called salterns, became the perfect setting for salt to form—thanks to the sun and the natural heat and dryness of the Mediterranean climate.
Here’s how it worked: The ponds were flooded with seawater and then sealed off. Over time, under the hot sun, the water would slowly evaporate, leaving behind a crunchy layer of salt crystals on the bottom. Once enough salt had formed, workers would harvest it—scraping it up by hand or with wooden tools.
But they didn’t stop there. Even natural salt has some unwanted extras—like calcium and magnesium salts, which can affect taste and texture. To clean it up, they gave the crystals a rinse with brine (extra-salty water) or fresh seawater. This step helped wash away the impurities, leaving behind a purer, whiter product.
At the time, this method was the cheapest and most common way to make salt—especially in hot, dry regions with the right kind of coastline. It didn’t require firewood, metal pans, or complicated tools. Just some clever water management and a whole lot of sunshine.
Even today, solar salt pans like these are still in use in places like France, Portugal, and India. It's slow, low-tech, and beautifully simple—and a great reminder that some of the best ideas are also the oldest.
Ancient Period Europe
How Sea Salt Helped Found Rome: The Origins of the Eternal City
Rome wasn’t built in a day—but it might have started with a handful of sea salt.
Around 750 BC, salt was big business in central Italy. The Sabines ran the Via Salaria—the Salt Road—moving sea salt from the Tyrrhenian coast across the Apennines to the Adriatic. They even charged tolls in salt, known as salarium—the origin of our word salary.
Meanwhile, to the northwest, the wealthy Etruscans—especially in their richest and most powerful city of Veii—needed salt. But their only production site was far inland at modern-day Volterra, way off trade routes. It was easier and cheaper to buy salt from the Sabines, who sourced it from the coastal lagoons at the mouth of the Tiber River near a small town called Ostia.
With high demand from nearby cities like Veii and little competition along the Tyrrhenian coast, Ostia's salt production was a money-printing business.
But flat coastal land made Ostia vulnerable. To protect their new wealth, the traders looked upstream and found the perfect spot: seven defensible hills along the Tiber, right on the Salt Road. Close to trade, easier to protect.
And from that smart move in 753 BC, Rome was born.
Middle Ages Europe
Venice: The Sea Salt Empire of the Adriatic
Long before Venice became known for its canals and art, it built its power on something far more practical: salt.
Since the 7th century AD Venice produced sea salt in it's famous lagoon. But beginning in 1281 AD, Venice rose to international power by securing control over the salt trade in the Adriatic Sea. At a time when salt was essential for food preservation, medicine, and livestock, it was more than a seasoning—it was strategic currency.
Through a mixture of cheque book diplomacy, alliances with the pope, and military strength, Venice established a monopoly on salt distribution in much of the eastern Mediterranean. Venetian merchants were obligated to import salt into the city. In return, they received a state subsidy known as the ordo salis. This system ensured a steady inflow of salt into Venice, which the government then resold at a profit to monopolized markets across Italy, Dalmatia, and Greece.
Revenues from the salt trade funded the construction of palaces, the building of merchant and naval fleets, and the expansion of Venice’s economic and political influence for centuries.
In short, Venice’s rise wasn’t just driven by maritime trade—it was powered by a calculated and state-controlled salt economy. The city’s foundations may rest on mud and stone, but its legacy was built, in large part, on salt.
Modern Period Asia
The Salt March: Gandhi’s Peaceful Protest That Shook an Empire
In 1930, Mahatma Gandhi led one of the most powerful acts of civil resistance in modern history—the Salt March to the sea salt pans of Gujarat.
At the time, salt in India was heavily taxed by the British colonial government. Worse still, Indians were forbidden from collecting or producing their own salt—even from the shores of their own country. This wasn’t just about salt—it was about economic control, colonial injustice, and national dignity.
Gandhi chose salt as the symbol of protest because it touched every Indian life, rich or poor. It was a basic necessity—yet even that was being monopolized by the British.
On March 12, 1930, Gandhi set out from his ashram in Sabarmati, near Ahmedabad, on foot. Over the course of 24 days, he walked 387 kilometers (240 miles) to the coastal village of Dandi, in the center of sea salt production—Gujarat. Along the way, thousands of Indians joined him—transforming a quiet march into a mass movement.
On April 6th, Gandhi reached the Arabian Sea. In open defiance of British law, he collected a handful of salt from the shore, symbolically breaking the colonial salt monopoly. This act of peaceful resistance sparked a nationwide wave of civil disobedience.
Within a year, over 60,000 Indians—including Gandhi himself—were arrested during similar protests across the country. But the British could not silence the movement. Gandhi was released soon after his arrest, and the momentum continued.
Though Indian independence would not come until 1947, the Salt March marked a turning point. It galvanized the population, unified disparate struggles, and inspired global figures like Dr. Martin Luther King Jr. in the fight for civil rights.
One of the British Empire’s harshest and most symbolic taxes became the first to be scrapped. What began as a simple act—gathering salt from the sea—became a crystallized revolution.
Middle Ages Asia
Bohai Bay: Beijing’s Ancient—and Massive—Sea Salt Source
Just east of Beijing, along the shores of Bohai Bay, lies one of China’s oldest and most productive sea salt-producing regions. Sea salt has been harvested here for over a thousand years, just about when Beijing started to grow important within the Chinese Empire.
Salt taxes were a major source of revenue for the Chinese state, and therefore Bohai Bay was an important asset for Beijing. The government tightly controlled salt production and trade, using it to fund everything from infrastructure to the military. In fact, the salt tax was so important that some historians call it one of the earliest examples of state-controlled monopoly economics.
Fast forward to today, and Bohai Bay is still a salt giant. Modern evaporation ponds and large-scale operations around the bay now produce over 20 million tons of salt annually—most of it through solar evaporation, just like in centuries past.
From ancient emperors to modern industries, Bohai Bay’s salt has helped power China for over a millennium. It’s not just a seasoning—it’s part of the country’s historical and economic foundation.
Middle Ages Europe
Fleur de Sel: The Delicate Crown Jewel of Sea Salt
Not all sea salt is created equal—and none is quite as prized as fleur de sel, often called the “caviar of salts.” Harvested with care and steeped in tradition, it’s one of the most expensive salts in the world. But why?
Unlike ordinary sea salt, which crystallizes at the bottom of salt pans, fleur de sel forms on the surface—a thin, fragile crust of fine salt crystals. These crystals only appear under very specific conditions: calm, dry weather and light, steady winds. The moment the weather shifts, they disappear.
Because of its delicate nature, fleur de sel must be harvested entirely by hand, often using traditional wooden rakes. This artisanal process has been practiced for centuries, particularly in the salt marshes of Brittany, France, where the name—meaning “flower of salt”—originated.
What makes it so valuable isn’t just how it’s made. Fleur de sel is exceptionally pure, with a light, flaky texture and a clean, subtle flavor. It melts gently on the tongue and adds a perfect finishing touch to everything from grilled vegetables to fine chocolate.
Modern Period America
Sea Salt and the Settling of the US West Coast
When the earliest American colonies reached the West Coast, they didn’t just search for gold—they needed salt. And the Pacific shoreline had plenty to offer.
In California, one of the first major salt suppliers was the South Bay Salt Works near San Diego, established in the 19th century. Using coastal lagoons and solar evaporation, it became a vital source of sea salt for early settlers and industries.
But it was the San Francisco Bay that truly became the powerhouse. With its wide, shallow marshes and sunny, dry climate, the Bay Area was ideal for large-scale salt production. Over time, it grew into the largest supplier of sea salt on the U.S. West Coast—a role it continues to play today.
From preserving food to fueling industry, salt was essential to westward expansion—and the Pacific’s salt pans helped make that possible.
Modern Period America
Nationalization in Mexico: From Global Sea Salt Giant to Cautionary Tale
Along the remote Pacific coast of Baja California, Mexico is home to the largest saltworks in the world: the Ojo de Liebre Lagoon. This vast operation, stretching across desert and coastline, has been a cornerstone of industrial salt production for decades.
The story begins in 1954, when an American logistics entrepreneur founded the saltworks to take advantage of the region’s ideal climate and geography. With abundant sunshine and dry conditions, the lagoon’s solar evaporation ponds quickly became highly productive—eventually generating millions of tons of salt each year.
By 1973, the founder sold the company to its primary customer: Mitsubishi, the Japanese industrial conglomerate. Mitsubishi expanded operations and maintained steady exports for decades. However, due to Mexican foreign ownership laws, the company was eventually required to form a partnership with the Mexican government.
Then, in 2024, under President Andrés Manuel López Obrador, Mexico took a bold step—fully nationalizing the saltworks by forcing Mitsubishi to sell its 49% stake. Mitsubishi responded by canceling all salt orders, triggering a sharp decline in exports. What had been a globally connected enterprise suddenly found itself isolated, with ripple effects across the local economy of Baja California.
The Ojo de Liebre story is a striking example of how geopolitics, economics, and natural resources intersect—and how complex the outcomes of government intervention in global industries can be.
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Turning Up the Heat: Boiling the Ocean for Salt
Boiling seawater is the older and more labor-intensive method. It involves collecting seawater and then heating it over a fire or in metal pans until the water evaporates and only salt crystals remain. This process can take hours—or even days—depending on the size of the batch and the fuel available.
Boiling is often used in cooler, wetter regions where the sun alone can’t do the job. It allows for year-round salt production, but it requires a constant supply of wood, coal, or other fuel, making it energy-intensive and more expensive.
This method tends to produce smaller, denser crystals, and often results in smoky or mineral-rich flavors—which is why some artisanal salts (like the Philippines' asin tibuok) are made this way.
Middle Ages Europe
Maldon Sea Salt: A Crystal Crafted by Nature and Tradition
When chefs, like Jamie Oliver, and home cooks reach for Maldon Sea Salt, they're not just seasoning food—they're tapping into a tradition over a thousand years old.
Nestled along the Blackwater Estuary in Essex, England, the town of Maldon has been producing sea salt since at least the medieval period. What makes this location special is its unique coastal environment: shallow tidal marshes, mineral-rich estuary waters, cool breezes, and low rainfall—a rare combination for northern Europe.
These natural conditions help create the perfect brine for salt production. As the water is gently heated, it forms Maldon’s signature pyramid-shaped flakes—light, crisp, and easy to crumble between your fingers. It’s a texture that chefs love and a finish that elevates everything from grilled vegetables to dark chocolate.
Maldon’s salt-making process is still largely traditional. Small batches are hand-harvested, and no additives are used—just seawater, heat, and time.
Middle Ages Asia
Asin Tibuok: The Sea Salt "Dinosaur Eggs" of the Philippines
In the Philippines, salt-making is more than a craft—it’s a living tradition. One of the rarest and most striking products of this heritage is asin tibuok, a type of salt often described as looking like a “dinosaur egg.”
The method dates back centuries and originates from the Visayan region. It’s a labor-intensive, artisanal process passed down through generations. Traditionally, salt-makers burn driftwood to produce ashes, which are then used to filter seawater. This ash-filtered brine is boiled in clay pots—called banga—over open fires for many hours.
As the water evaporates, large, dense salt crystals form inside the pot, creating a solid, smoky salt sphere. The result is not just visually unique—it has a distinct flavor profile, mildly sweet and earthy, thanks to the ashes and traditional materials.
Once common in many parts of the Philippines, asin tibuok is now considered rare and artisanal, produced only by a few communities preserving the technique. These salt “eggs” are prized not only for their taste but also for their cultural significance—a powerful reminder of the Philippines’ rich culinary and coastal heritage.
Middle Ages Asia
Salt and Fire: Indonesia’s Volcanic Ash Sea Salt
In parts of Indonesia, salt-making is more than just evaporation—it's a striking blend of ocean, fire, and volcanic earth.
Along the coasts of volcanic islands like Bali and Java, traditional salt farmers have developed a unique method: they sprinkle seawater over beds of black volcanic ash, allowing the ash to evaporate the water fast and concentrate the salt.
Once the ash is fully saturated, it gets washed with more seawater creating a strong brine. The brine is then boiled in large pans over open fires, slowly evaporating into rich, mineral-laced sea salt.
This method produces small-batch, artisanal salt with a slightly earthy flavor and a distinct mineral profile, thanks to the volcanic ash. It's labor-intensive, deeply local, and reflects centuries of adaptation to Indonesia’s volcanic landscapes and coastal resources.
Modern Period America
Boiling Seawater for Survival: Sea Salt and the Confederate South
During the American Civil War, salt wasn’t just a kitchen staple—it was a strategic resource. Without it, armies couldn’t preserve food, civilians couldn’t cure meat, and entire supply lines were at risk. So when the Union blockade choked off southern trade and targeted saltworks, the Confederacy scrambled for solutions.
One of the most desperate yet determined responses came from the Gulf Coast of Florida. There, the Confederate government and local civilians turned to the sea—boiling seawater along the coastline to produce salt in makeshift operations. These small, scattered saltworks became vital to feeding soldiers and communities alike.
The state of Florida officially permitted and encouraged this practice even to immigrants, recognizing how essential salt had become. But the effort didn’t go unnoticed. The Union Navy, aware of salt’s critical role, launched raids, bombardments, and blockades against these humble saltworks. Small boiling sites, often hidden in mangrove swamps or tucked behind dunes, were constantly shelled and destroyed.
Despite the risks, the salt boiling continued along the entire Southern coast—factories were often rebuilt just days after being destroyed. It was a quiet but vital front in the war effort, showcasing how something as simple as salt could become a matter of logistics, resilience, and survival.
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Buried Brine, Surface Shine: Evaporating Rock Salt Brine
Beneath Earth’s surface lie vast deposits of rock salt, formed from ancient seas that dried up millions of years ago. It is covered by further sediments and over millions of years compressed into what geologists call evaporite halite.
If such geological layers are permeable and groundwater-bearing, they are called salt aquifers and the water can become highly concentrated brine. To extract it, producers drill wells and pump the brine to the surface, where nature takes over.
In hot, dry climates, this brine is spread into large, shallow evaporation ponds, where the sun and wind slowly remove the water, leaving behind pure salt crystals. This method—solar evaporation—is clean, cost-effective, and energy-efficient. It works the same way as seawater pans.
Modern Period America
Morton's Desert Salt and Arizona’s Post-War Boom
Just west of Phoenix, beneath the arid landscape of Glendale, lies a vast subterranean treasure: the Luke Salt Body, an immense deposit of nearly pure halite stretching across approximately 40 square miles. Enough table salt to supply the US for 200 years.
Formed from ancient evaporated lakes, this geological marvel remained untapped until 1969, when the Southwest Salt Company began extracting brine from depths of up to 1000 meter (3,600 feet) using solution mining techniques. The brine was then channeled into shallow solar evaporation ponds, where Arizona's intense sun and low humidity facilitated efficient salt crystallization.
This venture provided a significant economic boost to Glendale and the surrounding West Valley region, supporting industries ranging from water softening to agriculture. The success of the operation attracted attention, and in 1985, Morton Salt acquired the facility, continuing its legacy of innovation and production.
Today, the Glendale saltworks stands as a testament to the region's resourcefulness, turning a hidden geological feature into a cornerstone of economic development.
Middle Ages Asia
Salt in the Clouds: Tibetan Wooden Salt Pans in the Himalayas
High in the mountains of Tibet, far from ocean coasts or industrial mines, salt has long been harvested in one of the most remote and breathtaking regions on Earth.
Near the Lancang River—known downstream as the Mekong—the Naxi people and other Tibetan communities have for centuries produced salt using a unique method adapted to the high-altitude environment. Brine-rich springs bubble up from beneath ancient lakebeds, remnants of a time when this land was covered by a prehistoric sea.
To collect the salt, local producers channel the brine into terraced ponds, letting the powerful sun and dry mountain air slowly evaporate the water. The resulting crystals are hand-harvested, often forming distinctive reddish or pinkish hues due to natural minerals in the soil.
Ancient Period America
Salt Without Money: The Ancient Economy of the Salinas de Maras
High in the Andes Mountains of Peru, at an altitude of over 3,200 meters (10,000 feet), lies a remarkable salt complex that predates the Inca Empire and still operates today: the Salinas de Maras.
Just 50 kilometers from Cusco, the heart of the Inca world, these salt terraces are fed by a natural saltwater spring that emerges from a rock salt deposit in the mountainside. Over centuries, this brine has been channeled into thousands of shallow, terraced evaporation ponds, where the sun slowly draws away the water, leaving behind crystals of high-quality salt.
This process is especially productive during the dry season—from May to October—when salt farmers flood the pans multiple times per month and harvest about once. The top layer yields the finest culinary salt, while deeper layers are collected for livestock and industrial use.
But what makes Maras even more fascinating is how it fit into the Inca economy, which functioned without money. Instead of a currency-based system, the Inca operated on a model of reciprocal labor and redistribution. Salt from Maras was bartered at seasonal trade fairs for goods like potatoes, maize, or textiles from other regions.
Every Inca citizen owed labor days to the state under a system known as mit’a. In return, the empire provided essentials—including salt—as part of a centrally managed supply system. This created a highly organized, yet moneyless, economy that kept vast territories running smoothly.
Today, the Salinas de Maras remain in operation, still worked by local families, still using the same techniques, and still echoing the rhythm of a civilization that valued salt not just as seasoning—but as structure.
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Deep Heat: Extracting Salt by Boiling Brine from Below
In regions where speed and consistency matter more than cost, the brine is heated in large tanks or boilers until the water evaporates, leaving pure salt behind. This method allows year-round production, even in cloudy or cold climates, and gives manufacturers tight control over purity and crystal size.
However, boiling comes with a cost. It requires large amounts of energy—from wood, gas, electricity, or steam—which makes it more expensive and less sustainable than sun-powered methods. The more so the lower the salt concentration in the brine. That said, it's often the go-to process for industrial-grade salt, where purity and speed are paramount.
Middle Ages America
Avery Island: Louisiana’s Ancient Salt Island
Long before it became famous for Tabasco sauce, Avery Island in Louisiana was known for salt. Located near the mouth of the Mississippi River, Avery Island is part of a cluster of five major salt domes in the region—a natural formation created by ancient seabeds pushed upward through layers of sediment. The region’s Native American tribes discovered its value centuries ago, long before European contact.
These coastal communities harvested briny spring water that bubbled up from the shallow rock salt deposit just beneath the surface. By boiling the brine, they produced pure salt—a highly prized commodity in a time without refrigeration.
This salt was then traded widely across the continent. Archaeological evidence shows it reached agriculturalist tribes as far north as Ohio and Illinois, and west to Texas and Arkansas—a testament to the island’s importance in early North American trade networks.
After the U.S. Civil War, commercial rock salt mining began on the island using shafts, tunnels, and galleries carved into the salt dome itself. Salt from Avery was sold for just $9 per barrel, dramatically undercutting the competition and turning the island into a key source of industrial salt in the Reconstruction-era South.
From prehistoric trade to postwar industry, Avery Island is more than a culinary curiosity—it’s one of North America's oldest and most enduring salt sites.
Ancient Period Europe
Salzkammergut: Where the World's Salt Story Begins
Tucked between the alpine lakes and mountains of Austria and Bavaria lies the world's earliest salt mining region: the Salzkammergut—literally, the “Salt Chamber Estate.” For 7,000 years, this landscape has been shaped not just by glaciers, but by salt.
As far back as 800 BC, the early Celts were already mining salt here, carving deep tunnels into the mountains and using the precious mineral to preserve meat—which was important in the cold and wet climate of central Europe. Salt and cured meats helped fuel Celtic communities and were the foundation for their long-distance trade.
By the Middle Ages, salt production shifted from mining to brine extraction methods that involve carving chambers into the rock salt and flooding them. In modern days this has shifted again to brine extraction through boreholes.
While both the Salzkammergut's and it's biggest city Salzburg's names are quite on the nose, many more towns in the region are named after salt. They bear variations of “Hall”, from the Celtic and also Greek word "hal" for salt, in their name, such as Hallstatt and Hallein. The same goes for other towns like Halle, Schwäbisch Hall, and Bad Reichenhall—each one a former salt capital with its own story and mines.
In 1829, bordering Austria and Bavaria signed the oldest still-valid bilateral treaty in Europe, the Salinenkonvention, which outlined shared rights to mine salt and log wood for fuel. It is basically a writeup of a verbal agreement that is even 600 years older.
The Bavarian-side saline in Bad Reichenhall today produces about 50% of the table salt sold in Germany. Meanwhile, the Salzkammergut is better known today for tourism, lakeside villages, and breathtaking views—but beneath it all lies a deep vein of history.
Modern Period Europe
Graduation Towers: Where Salt Meets Spa in Central Europe
At first glance, they look like giant wooden walls rising out of spa towns in Northern Germany and Central Europe—but these impressive structures aren’t sculptures. They’re called graduation towers, and they’ve been used in salt production since the 16th century.
Brine is pumped to the top of the tower and allowed to trickle down through dense layers of blackthorn branches. As it drips, the water slowly evaporates, and the salt concentration increases—essentially "graduating" the brine until it's strong enough for salt harvesting.
But there’s more. As the brine evaporates, it releases a fine mist of salty air into the surrounding environment. This mineral-rich air is believed to have therapeutic effects, especially for the lungs and respiratory system. Over time, these walls and towers became central features in European spa towns, blending salt production with early ideas of preventative medicine.
Places like Bad Dürkheim, Bad Salzuflen, and Ciechocinek in Poland still maintain their graduation towers—not just for tradition or tourism, but for visitors seeking a deep breath of history… and brine.
Ancient Period Asia
Zigong Well Salt: China’s Ancient Brine and Bamboo-Piped Gas
In the heart of Sichuan province, lies one of the oldest and most innovative centers of salt production in the world: Zigong—rich in brine aquifers and rock salt deposits.
As early as the Han dynasty, locals were extracting brine from deep wells and boiling it off to harvest salt. The region’s underground brine has an exceptionally high salinity—around 50 grams per liter—making it economically viable to use wood fires to evaporate the water.
By the 19th century, as local forests were nearly depleted, Zigong entered a new chapter of innovation: the discovery of natural gas. Ingeniously, workers piped this gas to the saltworks using hollowed-out bamboo tubes—a technology well ahead of its time. This switch from wood to gas revitalized Zigong’s salt industry, and made it one of the most productive inland salt centers in Chinese history.
Zigong salt isn’t just abundant—it’s highly regarded. In central China, it’s often compared in quality to Fleur de Sel from France and Himalayan salt from Pakistan.
Ancient Period Asia
Heijing: Marco Polo's Top Salt Destination in Yunnan, China
Tucked into a narrow mountain valley in Yunnan Province, the small town of Heijing once stood as a mighty inland center of salt production and trade. Though little-known today, Heijing was once so wealthy from its salt that locals referred to it as the "Salt Capital of Southwest China."
The secret to Heijing’s success lay underground. The town sat atop brine-rich aquifers, which local communities had been tapping since Neolithic times. Heijing rose to prominence during the Tang dynasty (7th–10th century). Using deep wells, the locals brought up the brine and boiled it in large iron pans to extract salt—a process powered for centuries by wood fires.
What made Heijing unique wasn't just the salt, but the strategic trade networks it was part of. The salt produced here supplied much of Yunnan, Guizhou, and even parts of Burma and Tibet, moving along rugged caravan routes. At its peak during the Ming and Qing dynasties, Heijing was so prosperous that it developed into a small but sophisticated town, complete with ancestral halls, Confucian schools, and traditional mansions—many of which still stand today.
Salt was even used as currency. The Venetian traveler Marco Polo, visiting Yunnan in the 13th century, remarked:
“These rascals have none of the great Khan’s paper money, but use salt instead.”
At the time, the "Khan" was Kublai Khan, the Mongol emperor of the Yuan dynasty, and indeed, salt remained a form of currency in central China until the 19th century.
Modern Period America
How Salt Built the Erie Canal: Syracuse and America’s First Superhighway
Salt springs in upstate New York were first used by the Delaware Tribes, and later by the Onondaga Nation, whose land rights played a crucial role in what came next. Following a treaty with the State of New York, the region's early white settlers began to extract salt through brine boiling, creating one of the most important inland salt industries in early U.S. history.
The salt from Syracuse didn't just supply local needs—it provided for much of the northwestern American frontier in the 18th and 19th centuries. The industry became so profitable that royalties from salt production—$2.3 million, to be exact—funded a third of the landmark civil engineering project of the time: the construction of the Erie Canal.
Completed in 1825, the 584 km (363-mile) canal connected the Great Lakes, Buffalo, Syracuse, Albany, and other key upstate cities to the Hudson River, New York City, and ultimately the Atlantic Ocean. Often called “The Nation’s First Superhighway,” it was second in length only to China’s Grand Canal and transformed American trade. The canal’s success, in many ways, was built on salt.
Syracuse's salt boom lasted through the 19th century, until the original deposits were exhausted around 1900. But the industry didn’t end there. Just to the west, in Livingston County, a massive underground mine took over—and today, it’s the largest salt mine in the United States, producing over 6 million metric tons per year.
Other nearby salt giants include mines in Detroit, Michigan, and Whiskey Island near Cleveland, Ohio. But the global heavyweight is just across the Canadian border: the Goderich salt mine in Ontario, the largest in the world, producing 7.5 million metric tons annually.
So next time you think about salt in your kitchen, remember—one of the greatest public works projects in U.S. history started with boiled brine in upstate New York.
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Work in Progress
This article is a work in progress. I hope to have finished it by the end of June 2025.
The following additional topics and stories will be covered:
Salt Lakes: Natural Reservoirs of Crystal Wealth
Lake Yuncheng, China -> 6000 BC, China’s oldest saltworks
Siwa Oasis -> First civilization to preserve food with salt
Great Salt Lake, UT -> US salt production
Dead Sea, Middle East -> first health resort
From Dust to Crust: How Salt Deserts Leave Behind a Salty Legacy
Danakil Depression -> salt harvested directly with hoes
Lake Natrun, Egypt -> Mummies
Taghaza -> Mansa Musa
Salar de Uyuni -> largest salt flat, 50% of the world's lithium reserve
Salar de Atacama -> 27% of the world's lithium reserve
Solid Gold: Digging into the World of Rock Salt Mining
Wieliczka, Poland -> Cathedral, Casimir the Great
Zipaquira, Colombia -> El Abra, Muisca (500 BC), Cathedral
Himalayan Pink Salt -> Khewra and Alexander the Great
Persian blue salt -> Potassium Chloride veins
Duzdagi mines -> Eastern Silk Road Tabriz to Erzurum
Cheshire salt mines -> Roman Condate
Asse, Germany, potash mine -> Nuclear waste
Great Lakes -> Goderich (largest in the world) Canada, Livingston County NY (largest in the US), Whiskey Island OH, Detroit MI
Hutchinson, Kansas -> First salt mines west of the Mississippi
Louisiana salt domes -> Avery Island, Cote Blanche (15% of US de-icing salt)
Salt from the Ground Up: Brine from Soils and Vegetation
Burning Salty Peat -> German, Dutch, and UK coasts
Salt from plant ashes
Boiling salty soil
No Salt, No Solution? What Happens When Salt Isn’t Available
Imports -> Scandinavia, Confederate States
Sub-Saharan Savannah -> Taghaza salt for Gold Trade
Polynesia -> Seafood
Power, Borders, and Brine: The Salty Side of Global Politics
Taxes -> China
Monopolies -> China, Roman Empire: 284 - 305 Diocletian
Wars -> US Civil War, Venice (+ Pope): Padua (1304), Ferrara (1480s), Naples (1550s)
Rebellions -> Gabelle
Colonialism -> East India Company / Gandhi, El Paso Salt War
Salt Today: High-Tech Crystals from Ancient Sources
USA -> Modern salt production stats
APPENDIX
Salty Geo-Data: Where to Download and how to Process
The NASA WorldWind framework that is being used for the worldciv simulation software project works the easiest with KML files. Those also work with all the other geo-data tools in use. Therefore, this guide describes how to transform whatever is provided to KML.
Join our Patreon community and download processed files and latest versions of manual additions.
The goal of the geo-data processing described is to enable worldciv to draw a 20x20 km square on the globe and geometrically compute which resources are in it. In this case point-like rock salt deposits, how many km2 of salt lakes and playas, how many km of coastline and how much of it is suitable terrain for sea salt pans, and whether the area is in a climate suitable for solar evaporation.
Tools:
GDAL: A CLI translator library for raster and vector geospatial data formats.Download: https://gdal.org/en/stable/index.html
GRASS GIS: A powerful computational engine for raster, vector, and geospatial processing. Comes with a UI.Download: https://grass.osgeo.org/
Google Earth Pro: Displays satellite image layers and Google's locations for orientation on the map. Customize it to have better pins and icons on the maps.Download: https://www.google.com/earth/about/versions/
Extract Major Rock Salt (Halite) Deposits
Source: USGS MRData – Mineral Resources Data
Dataset: Major Mineral Deposits of the World
Steps:
Download the shapefile version of the "Major mineral deposits" dataset.
Extract the ZIP file to a directory (e.g., ~/Downloads/ofr20051294-csv/ofr20051294/).
Use ogr2ogr to extract salt-related sites:
ogr2ogr -where "commodity ILIKE '%Salt%' OR commodity ILIKE '%Halite%'" -f KML salt.kml ~/Downloads/ofr20051294-csv/ofr20051294/ofr20051294.shpI supplement the dataset manually with data from Wikipedia on global salt mining, but also from random sources on the internet or accidental mining finds in Google Earth.
Download Playas (Dry Lakebeds)
Source: Natural Earth
Dataset: Physical Vector Data Themes – Playas
Steps:
Go to the Natural Earth data page and download the 1:50m Physical Vectors – Playas dataset and extract the ZIP archive.
Drag and drop the ne_50m_playas.shp file into Google Earth.
Right click on the Google Earth layer -> Save Place As -> Select KML as the file type
Process Salt Lakes (Endorheic Lakes)
Warning: This is an unsatisfactory approximation. Since I couldn't find a satisfactory solution, besides manual drawing, I went with a low-effort approach for now.
Lakes without an outflow, called endorheic, tend to be salt lakes. Every river is a tiny bit saline, some of them a little more. If a lake does not have an outflow, then the way they lose water typically is evaporation only. The salt, however little, stays behind in the lake and will necessarily turn it salty over a long period of time.
The problem is that their salinity greatly varies. For example, the Caspian Sea is technically such an endorheic lake. It's salinity is on average 1/3 that of the seawater, much less in the north, and much more in the south. It's Garabogazköl lagoon is one of the saltiest bodies of water on earth.
Source: WWF & Center for Environmental Systems Research
Dataset: Global Lakes and Wetlands Database (GLWD)
Steps:
Go to the GLWD link above and download the GLWD Level 1 shapefile dataset.
Extract the ZIP file to a directory on your computer (e.g., ~/Downloads/GLWD-level1/).
Use ogr2ogr to extract closed-basin lakes:
ogr2ogr -where "MGLD_TYPE LIKE 'closed%'" -f KML saltlakes.kml ~/Downloads/GLWD-level1/glwd_1.shpI manually added ca 50 saline bodies of water from lists on Wikipedia but found their lists to be very incomplete. I would love some help with researching and adding them.
Download Coastline Data for Sea Salt and Sea Salt Pans 1/3
Source: Natural Earth
Dataset: Physical Vector Data Themes – Coastline
Steps:
Download the 1:50m Physical – Coastline shapefile.
Drag and drop the ne_50m_coastline.shp file into Google Earth.
Right click on the Google Earth layer -> Save Place As -> Select KML as the file type
Manually remove the Caspian Sea feature which is not part of the open ocean and also included in the lakes dataset that worldciv uses. Keep it if fits your purpose.
Process Coastline Terrain Data for Sea Salt Pans 2/3
Work in progress.
Ideas:
Filter wetlands data for lagoons and salt marshes from GLWD V3 with ArcGIS
Filter more fine-grained elevation data, e.g. GMTED 2010, for coastal flatlands of max 1-3 meters elevation
Process Climate Data for Solar Evaporation and Sea Salt Pans 3/3
Get global climate zones and filter for those that are warm and dry enough to allow for salt production by solar evaporation. Köppen Geiger class labels fully written out:
1: Af => Equatorial, fully humid
2: Am => Equatorial, monsoonal
3: As => Equatorial, summer dry
4: Aw => Equatorial, winter dry
5: BSh => Arid, Steppe, hot arid
6: BSk => Arid, Steppe, cold arid
7: BWh => Arid, Desert, hot arid
8: BWk => Arid, Desert, cold arid
9: Cfa => Warm Temperate, fully humid, hot summer
10: Cfb => Warm Temperate, fully humid, warm summer
11: Cfc => Warm Temperate, fully humid, cold summer
12: Csa => Warm Temperate, summer dry, hot summer
13: Csb => Warm Temperate, summer dry, warm summer
14: Csc => Warm Temperate, summer dry, cold summer
15: Cwa => Warm Temperate, winter dry, hot summer
16: Cwb => Warm Temperate, winter dry, warm summer
17: Cwc => Warm Temperate, winter dry, cold summer
18-32: Dfa => Snowy and polar climates are too cold
This list is a subjective choice. Dear sea salt experts or meteoroligists of the world, please comment.
Source: World Köppen-Geiger Climate Classification
Reference: Kottek, M., J. Grieser, C. Beck, B. Rudolf, and F. Rubel, 2006: World Map of the Köppen-Geiger climate classification updated. Meteorol. Z., 15, 259-263. DOI: 10.1127/0941-2948/2006/0130.
Steps:
Download the Köppen-Geiger raster dataset.
Import into GRASS GIS. File -> Import raster data -> r.importSource File: Map_KG-Global/KG_1986-2010.grd
Convert to a filterable vector format: Raster -> Map type conversions -> r.to.vectInput raster card: KG_1986-2010Output raster card: climate_zonesOutput feature type: area-> Attribute tab -> Use raster cell values as category names-> Run
Filter for regions with warm and dry climate types: Vector -> Feature selection -> v.extract Input vector card: climate_zonesOutput vector card: sea_salt_climate_zones-> Selection tab -> Category values: 3,4,5,7,9,12,13,15,16-> Run
Export to KML: File -> Export vector map -> v.out.gr Input vector map: sea_salt_climate_zonesOutput data source: Browse to Downloads folder -> Name your file sea_salt_climate_zones.kmlData format: KML
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