Idrija: Slovenia’s Hidden Gem

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In the late 15th Century, a bucket maker living in the rugged landscape of what is today Western Slovenia came across something unusual near a local spring. Metallic and heavy like an ingot, this particular metal ran across the palm of his hand as easily as water. The mystified peasant took his find into the town of Loka many kilometers away, where a goldsmith identified the substance as mercury. 

Statue in honor of the mercury miners of Idrija

Thus, began the history of Idrija, or so the legend goes, and by the time its mines had closed in 1995, this small town clinging precariously along the banks of the Idrijca River would produce 13 percent of the world’s total output of mercury. Recently, I had a chance to visit Idrija, a UNESCO World Heritage site located far from the maddening crowds of Ljubljana and Lake Bled. The mines and the smelting plant are now open to the public, or as the case would be, me, since on this particular grey day, I happened to be the only tourist to venture this far into Slovenia’s hinterlands.

Despite being only a little over an hour away from the capital, Idrija seems to be on nobodies bucket list. Strangely, it was pretty much the only Slovenian town on mine. I guess I just have a thing for heavy industry and toxic materials. But before I could descend into the depths of the earth or admire the machinery that kept this place operating during the 20th Century, I needed to go up to a castle on a hill for some historical perspective.

Worth its Weight in Silver

Like all things in this town, Idrija’s renaissance castle is intrinsically linked to mercury. For this was not the seat of a lord or noble, but a palace for the mines administrators. Today, the castle serves as the historical museum and recounts the history of this fascinating town.

The discovery of mercury near the end of the 15th Century was especially fortuitous for the Hapsburg Empire, which came into possession of these lands around the same time. Because of its scarcity, mercury has always been a precious commodity, but the discovery of the Americas and its vast quantities of gold and silver made mercury not just valuable but a resource of the utmost strategic importance.

Gewerkenegg Castle housed the mine’s administration

Mercury is the key to the amalgam process, where metal binds to mercury to form an alloy. In the mid-16th Century, advancements in this process led to its use to extract silver from low-grade ore. It was around this time that the Hapsburgs acquired a large number of gold and silver mines with the ascent of Charles V to the throne of Spain. Between Idrija and another mercury mine in Almadén, Spain, the Hapsburg Empire held a virtual monopoly on the metal.

Mercury also led to some unique developments within Idrija itself. Forestry became an important side industry as the mine required an almost insatiable amount of wood for support beams and to burn in the furnaces. Trees were felled from the nearby hills, but transporting them into town was difficult work. To remedy this problem, engineers dammed the creeks running into the valley. The felled trees would be rolled into these dry streams. When the dam was open, a torrent of water would flush the logs into the Idrijca River where they were caught by a “rake.”

A more famous industry that grew up alongside the mine was lacework. As there wasn’t enough space for other forms of labor such as farming, woman turned to this craft to supplement their income and prevent idleness. Even today, Idrija is still famed throughout Europe for its bobbin lace.

Descent into Darkness

The 18th-century entrance to Anthony’s Shaft

Having finished with the museum, I was now ready to go through the very same entrance used by Idrija’s miners for centuries. My tour began in the 18th-century call room of Anthony’s shaft. Donning a hardhat and jacket, I was led by a guide through a narrow entrance leading directly into the mountain. 

“The first part of the shaft is narrow,” says my guide. “It is the oldest.” As we descended, he explains the history of mining in Idrija from digging with rudimentary tools to the more modern use of explosives and compressed air drills. “The drills were very efficient, but you can imagine the dust.” He flicked a switch, and a mockup of a modern drilling team comes to life. Smoke fills the corridor, lingering in the dim lights. “Of course, they would be doing this with only lanterns.” He motioned above to a strand of lines dangling from the ceiling. “These are just for the tourists.”

As the mine was modernized and made more efficient, a standardized process for removing ore emerged. When a vein of mercury was discovered, the miners would dig the ore out and dump it down a shaft. The hollow cavern would immediately be backfilled to prevent the town of Idrija from sinking. At the lowest tunnel, the ore would be collected on a minecart (which, when loaded, would weigh about 800 kilos) and pushed to an elevator. It was back-breaking work, and it wasn’t until the 1950s that basic safety equipment like hardhats and masks were standardized.

The water pump was built in 1790

Passing a chapel, we descended even deeper into the mine where pure mercury could still be seen, a constellation of small silver pearls against the dull red rock. A few meters further on, a timber beam stood splintered from the weight of its load. “The beams need to be constantly replaced because of the humidity” said my guide. “Water is the biggest problem in the mine.”

Indeed the maintenance required to keep the mine safe is extensive. Besides inspecting and replacing old beams, water needs to be continuously pumped out of the shafts and air pumped in. Previously, this was done by an enormous water wheel feed by one of Idrija’s numerous streams. It still stands just outside the town.

As I stood contemplating the still very real danger of collapse, the lights suddenly flickered off. There is a high pitched cackle and a piercing flash of light from deep down a black corridor. The light appeared again, this time closer. And again. Until, finally, a humanoid shape stood only a few meters in front of me. “It’s Prekmandlc, the pit dwarf, who likes to play pranks on miners when he’s in a bad mood,” says my guide in a rehearsed bit that probably plays well to the scores of school kids that come to the mine but seemed embarrassingly out of place between two grown adults standing in the dark.

Thankfully, the lights come back on, and we retraced our steps to the surface. Ok, so maybe the mine was a little cheesy, but there was still much more that I need to know. I had gotten a taste of what work was like in the mine, but what about the life of the miners? For that, I turned to a staff member at the Idrija Municipal Museum, who would show me one of their most important acquisitions, the home of a 17th-century miner.

Last House Standing

The banks of the Idrijca River

“There has only been one strike in Idrija,” said my guide, a young woman whose own family had been lured here by relatively high wages from Poland many centuries ago. “In the 17th Century, the administrator appointed by the Hapsburgs was abusive, so the miners went to the castle and beat him up.” She paused before adding flatly, “He was replaced.”

Despite the abysmal working conditions and the obvious health consequences of mining mercury, life here was in many ways above average. The high price of mercury not only meant higher wages, but it also gave the miners leverage. It was far easier and more efficient to keep them happy then attempt to exploit their labor for short-term monetary gain.

But that doesn’t mean that the miners didn’t have to sacrifice. Besides considerably shorter lifespans, miners also had to cope with cramped living conditions. There simply wasn’t enough room in Idrija due to the rough terrain. At times, the housing situation was so bad that if you were not directly employed at the mine, you were not even allowed to live in the town.

The 18th-century miner’s house in Idrija

Part of the solution to this problem was found in the house I was about to visit. Instead of building out, the miners built up. “The mine administrators would finance the construction of a miner’s home on the condition that the miner built three stories. The cost of construction would be recuperated by renting out the other floors,” said my guide. In practice, this meant up to 20 people living together and sharing one kitchen and an outhouse. The miner who had built the house had the luck of living on the second floor, which was larger than the third but warmer in winter than the first.

The house I visited was something of an exception. It included an indoor toilet that led to a slop box in the basement as well as a kitchen on both the first and second floors. For the times, this would have been considered a luxury. Nevertheless, a family of up to six would often have to share a space consisting of only two rooms and one bed barely large enough to accommodate a single person. “The youngest children would sleep in the drawers,” I was told. 

Over the years, the occupants added an additional annex to the house for traveling artisans. “When someone like a cobbler would come to town,” said my guide, “they would stay in this room and make shoes for the entire family for room, board, and a small payment.”

This particular abode was occupied until the mid-1900s when it fell in disrepair. “Idrija used to be full of these houses, but they found it cheaper to tear them down and build new ones rather than restore them for modern living.” Today, less than a dozen remain.

Purely Elemental

A drop of pure Mercury from the mine at Idrija

My final stop in Idrija was to the smelting plant. I had learned the history of the miners and how the ore was taken from the ground, but one piece of the story was still missing: the distillation process. Naturally occurring mercury is exceedingly rare, and it wasn’t long before the miners at Idrija had to resort to burning cinnabar (HgS) to extract mercury. When heated at a high enough temperature, the mercury evaporates, leaving the sulfur behind. To capture the mercury, early miners would burn the ore in sealed clay vessels. The mercury would turn to steam and then eventually condense inside another clay vessel placed on top. This method, however, was labor-intensive, and much of the mercury escaped during the process.

The introduction of the Spanish aludel furnace in 1750, though, changed mercury mining in Idrija forever. In this process, the ore is burned allowing the sulfur and mercury gases to pass through a series of condensers known as aludels.  The mercury would cool and collect into a basin below.

Part of the sorting mechanism used at the Smelting Plant

And this was more or less how mercury was distilled at the end of the mine’s life. Indeed, by the time the mine closed, the process had been nearly automated with ore traveling across the Idrijca River in suspended buckets, dumped into a sorter and crusher before being spewed out onto a conveyor belt to three rotary furnaces. As the ore turned slowly down the inclined steel tube lined with bricks, the mercury evaporated and collected in a condenser. The burnt ore was then efficiently, albeit unwisely, dumped into the river.

For nearly five centuries, mercury coursed, both literally and figuratively, through the veins of the men and women of Idrija. But today, the mines are empty; the machinery stands silent, and the once ever present black smoke no longer bellows from the furnaces. Nevertheless, life in Idrija continues in this resilient town that has escaped the fate of so many mining and heavy manufacturing communities across the globe. New cleaner industries like specialized parts manufacturer Kolektor have picked up the slack, employing thousands and making Idrija something of an anomaly: a small town that actually has a steady and youthful population.

If You Go

Idrija can easily be visited as a day trip from Ljubljana. Buses frequently run from Ljubljana’s train station and cost approximately €7 each way. Tickets to see the mine at Anthony’s Shaft cost €13 and the Hg Smelting Plant can also be visited for €8. Better is to buy the combined ticket for €18. While the mine will be fun for kids, the Hg Smelting Plant not only has the original machinery used to refine the ore prior to the mine’s closure but an excellent museum outlining the distillation process and the science behind the metal. It is also worth visiting the Idrija Municipal Museum for €7, which includes a guided tour of the Miner’s House and the Kamšt Water Wheel pump. 

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6 thoughts on “Idrija: Slovenia’s Hidden Gem”

  1. Thanks! I appreciate the feedback. There should be some more posts in the coming months as well as a possible format change.

  2. Years ago I owned shares of a company called New Idria Mining. Based in Idria, California, it was America’s only mercury mine in the 1970s. I always wondered where the name came from. I thought it was Spanish. Now I know! The company is gone. The mine closed. The areas is in an official “hazard zone,” and if you look at a map of California you can see this area clearly marked. It is south west of Fresno. But it is not because of the mercury. It’s the asbestos. Union Carbide ran an enormous asbestos mine nearby for many years.

    1. Hi Bob,

      It’s funny you mention that because I had never heard about New Idrija until I went to Slovenia and one of my guides brought it up. I guess they are kind of proud of the fact that someone named a town after them in the middle of California. Supposedly, its fairly well preserved, although I’m sure its fenced off for obvious reasons.

  3. Hey. I also visited the mine and the Hg Smelting plant and both of the sites were amazing. They perfectly show the history of mining and everything connected to the mercury. They also mentioned the New Idrija and New Almaden in California. With this information, they more showed how Americans just copied both names. But they are not specifically proud of it tho. For them, it’s just an interesting fact.

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