Geological randomness, Lewis Carroll’s mad hatter and a UNESCO Global Geopark.
Like so many others, this too is a story marked by chance. Legend has it that in 1490, Škafar, a craftsman in the remote Slovenian Alps, left his wooden pieces submerged in the water of his small well, as he did every night. The following morning, as he prepared to take them to the local fair, the pieces, soaked with water absorbed overnight, weighed more than Škafar remembered. With effort, he retrieved each piece one by one, and it was then that a brilliant liquid revealed itself at the bottom. Uncertain of its nature, Škafar collected the curious liquid in one of his wooden bowls, carefully transporting it to the fair in Škofja Loka. Dozens of people saw that dense, shiny, silvery liquid resting at the bottom of a wooden bowl, yet no one recognized it. No one, but an old goldsmith who, supported by decades-long experience, delivered the verdict that marked the birth of an industry that would sustain the Idrija region for nearly 500 years: mercury!
But was it truly chance? Or is what we call chance nothing more than a (improbable) combination of perfect geological conditions? And where does Lewis Carroll Mad Hatter fit in the story?
Dinaric Alps
Hidden Treasures of the Dinaric Alps: The 238-Million-Year Journey of the Idrija Mercury Deposit.
As we often do when the matter is geology, let us journey back in time.
At the extreme northwest of the Dinaric Alps - the mountain range that stretches from Slovenia along the Adriatic down to Greece - the Idrija Mineral Deposit, as it is known, was indeed discovered in the 15th century, but its formation is thought to have occurred 238 million years before, in the Triassic period (251 Ma - 201 Ma) of the Mesozoic Era.
At that time, the continental masses previously united to form the supercontinent Pangaea, and after a period of quiescence, had slowly begun to fragment, on their way to creating two other continents - Gondwana (South America, Africa, India, Antarctica, and Australia) and Laurasia (North America and Eurasia).
Geographical location of the Adriatic region and the Dinaric Alps.
Source: Webter et al. (2003).
This movement would eventually create the familiar configuration of the planet we know today. But not all continental masses were giants. Several others, smaller, just like solitary islands, emerged from what was then known as the Thetys Ocean - to the east - or Panthalassa, to the west. Amongst them, the Adriatic microplate, which movement in relation to the Eurasian and African plates is responsible for the creation of three mountain ranges: the Alps, Carpathians, Dinaric Alps, and Hellenics, as well as the Apennines.
And it was precisely the tensions created by the relative movement between these landmasses - in a process that eventually created the Alps, that continues to this day and generates earthquakes at times - that the secret accidentally discovered by Škafar, the craftsman, in 1490, was hidden. For not only mountains are formed when continents collide.
Continents configuration in the Early Triassic, 237 million years ago.
Deep beneath the surface, out of sight, high-temperature magmatic fluids rich in mercury circulated through the fractures in the rocks and the sediments deposited millions of years earlier, to form the world's second-largest mercury deposit (the largest, in Almadén, Spain, has been known and exploited since antiquity). As these fluids cooled, the cinnabar mineral (HgS) crystallized in cavities and fractures of the rocks, in a process known as epigenesis. But in Idrija (or what would become Idrija), geological fortunes played a winning hand. The hot mineral solutions rich in mercury reached the surface, spreading along the bottom and the waters of the region’s marshes. Wait… Marshes? But aren’t we talking about the Alpine region?! Well, not really, because at that time, the Alps were not yet the mighty mountains we see today and the region was located further south, in a geography with a much different climate.
This rare phenomenon led to the formation of layers known as Skonca, sedimentary deposits extremely enriched in mercury (up to 78% Hg). Due to the absence of sulphur, these rocks were also impregnated with native mercury, found in Idrija in economic quantities and purity of up to 99.9%.
Cinnabar ore.
For years, this remarkable geological coincidence turned the small town of Idrija, isolated and difficult to access, into one of the country's most important economic centres and a significant mining hub. Unsurprisingly, the finding wasn’t missed by the region's elites, and by 1580, all mining operations had already been controlled by the powerful House of Habsburgs. Subsequently, following the historical upheavals of the region, mercury mining in Idrija was controlled by Italy, Austria, France, and Yugoslavia. However, production remained indifferent to geopolitics, continuing uninterrupted between 1508 and 1977. At its peak, the mine employed over 1200 people. In 1991, the newly formed Republic of Slovenia finally took control of its own mineral resources. Of little avail. With ore prices steadily declining since the 1970s, not only due to the emergence of other producers with lower extraction costs, but also due to restrictions on the use of mercury in various equipments and daily objects because of its high toxicity, operations ended shortly thereafter, in late 1995.
“Over the nearly 500 years of operation, Idrija Mine extracted almost 13 million tonnes of cinnabar ore and 145,000 tonnes of native mercury from the depths from the earth, 13% of historical global production. ”
It employed thousands of people, many, probably the majority, suffered the physical consequences of the exposure to this highly toxic element. Nonetheless, as in all stories, there’s a silver lining. Alongside the ailments caused by mercury, the region also developed the earliest studies of occupational medicine, medical hygiene, and toxicology on record by Giovanni Antonio Scopoli, in the early 18th century. Observing the miners of Idrija for 15 years, this Italian physician and naturalist described the symptoms of chronic mercury poisoning in his work "De Hydroargyro Idriensi Tentamina" (Essays on the Mercury of Idrija). This would be a cornerstone for occupational medicine across the world. Save that information.
Giovanni Antonio Scopoli and his work "De Hydroargyro Idriensi Tentamina".
Artisanal and small scale mining.
Today, artisanal and small-scale miners, particularly in the Global South, still risk their health and lives in search of critical raw materials to meet the ever-increasing demands of industrial production. In fact, reports show that around 90% the world’s mining workforce is artisanal, 30% of which women. They represent 45 million workers who make their living by digging the earth, often driven by poverty, in search of cobalt, tin, tungsten and tantalum, as well as gold, diamonds, gemstones, coal and other minerals. It is also estimated that an additional 270 million people are indirectly supported by these activities.
Particularly in gold mining activities, mercury, used to amalgamate gold, is a serious health and environmental problem. Globally, this type of mining is considered the largest source of mercury pollution to the atmosphere and to water. UNESCO, through its International Geoscience Programme, is supporting research to understand how mercury pollution generated by these activities is transported, transformed, bioaccumulated and sequestered in Amazonian ecosystems.
“Artisanal and small scale mining activities represent 90% of this sector’s work force. Withouth them, the world would literally stop. Unfortunately it is also the major cause for mercury contamination. ”
Mercury, medicine and curse.
Throughout human history, mercury has been a constant presence. Known since at least 5000 BC, this metal, the only that remains liquid at room temperature, has been used for various purposes. In alchemy in search of lost youth or transmuting metals into gold; in medicine, where it was used to treat all kinds of ailments, from syphilis to melancholy, sometimes with more serious impacts on patients' health than the disease itself; and in industry, for gold amalgamation - as the Romans knew so well - or, centuries later, by Fahrenheit when creating the thermometer, which paved way to a myriad of other scientific and technical instruments. Mercury was so prevalent in 16th to 19th century societies that it may have been the hidden reason behind the name of one of the most famous characters of the English literature: Lewis Carroll’s Mad Hatter.
Although it is now acknowledged that Carroll drew inspiration for the character from Theophilus Carter, an eccentric Oxford furniture salesman known for his fondness for top hats and whose curious inventions included an alarm clock that flipped the bed, causing the "guest" to tumble, many readers still associate the Mad Hatter's behaviour with that of real-life hat makers of the victorian era. With reason as it was typical for Victorian-era hat makers to display symptoms such as tremors, slurred speech, and irritability. However, it wasn’t madness; it was poisoning. Throughout the 19th century, the felt used in hat making was treated with mercuric nitrate, a form of mercury we now understand to be highly toxic. After years of inhaling mercury vapours, hatters began to exhibit symptoms that, at the time, may have appeared to be nothing short of madness, they became the mad hatters and coined the expression “mad as a hatter”.
“There is a place like no place on earth. A land is full of wonder, mystery, and danger. Some say to survive it, you need to be as mad as a hatter. Which, luckily, I am.” - the Mad Hatter.
A new beginning.
After five centuries and approximately 700 kilometers of excavated tunnels, the memory of mercury mining in Idrija and all its heritage - including the oldest entrance to an underground mine gallery in Europe, known as Anthony's Main Road, the largest rotary furnace for cinnabar ore smelting in the world, and several dams built in the valleys of the region - were inscribed on the UNESCO World Heritage List in 2012 and included in the Idrija UNESCO Global Geopark a year later. The region is now a case-study of environmental recovery, and unlike many others around the world where the closure of mining pits dictated the beginning of a long decline accompanied by serious social and environmental challenges, the transition in Idrija was different. Initiated during the communist period, this transformation saw the emergence of two multinational companies that employ more workers today than the mines ever were able to, with the region registering an unemployment rate below the national average.
Interestingly, it appears that the future of mining will remain intertwined with this region. From 2016 to 2020, Idrija served as one of the test sites for the UNEXMIN project, which aimed to develop an autonomous system for robotic exploration of flooded underground galleries. With approximately 30,000 closed mines across Europe, a significant number of which are flooded and contain valuable raw materials, crucial for the energy transition and independence of the European Union, these systems and century-old mines are poised to play a pivotal role in the future of mining.
Will we soon witness the addition of new chapters to the already extensive history of mining in Idrija?
