A heritage of mercury mining and lace making

Year 1492: Columbus discovers America; Reconquista is finished; Lorenzo de'Medici dies in Florence. In a remote part of the then Venetian terra ferma, situated right near the borders of the Adriatic Sea and Black Sea water drainage basins, and of the Karst and subalpine regions, free mercury has just been discovered in a stream. Colonization begins; a new town spawns in a narrow valley, its name derived from Hydrargirum, the Latin for mercury. The mine is to become the world's second largest, after Almaden, Spain.

The region was volatile. Venice had to yield it to Austria in 1509. As of 1575 the mine was directly subject to the Austrian Emperor; consequently, most documents are nowadays to be found in the Vienna Hofkammerarchiv. From 1797 to 1813 the region was occupied by the French as part of the Illyrian provinces. Between WWI and WWII the region was part of Italy.

A complicated geological fault system necessitated digging of deep pits (recently reaching 400 meters), and fighting large quantities of intruding water. This made Idrija a center of technological innovation for centuries, attracting many famous people from Austria and other countries, and an important part of the scientific endeavor in Slovenia throughout its history.

After 500 years of operation, and after having produced 107,000 tons, or 13 percent of the world production of mercury, the mine is being closed due to low mercury prices and ore exhaustion. Idrija's industry managed to shift rather painlessly to being one of the largest world producers of small electric motors and their components, and to furniture-making.

The Idrija Lace lace is part of local tradition, and widely recognized. The craft was brought there a couple of hundred years ago by Czech or German families working in the mine or its headquarters. Basically, it was an appropriate activity in a culture not dependent on agriculture for survival. The Idrija lace is now registered as a trademark, and care is being taken to preserve the craft itself. The Idrija lace proper was established in 1870's and was made with 7 pairs of bobbins.

Idrija's coat of arms features a figure of the god Mercury modeled after a statue attributed to de Vries, c. 1610, and possibly to G. Bologna, and whose copy can be seen, for example, in the Rotunda of the National Gallery in Washington.

History of mercury mine

Mercury in Idrija comes in two guises: as cinnabar (mercury sulphide, HgS) rock inclusions, and as pure mercury, referred to as 'native' mercury.

In the beginning, ore was smelted in ceramic pots in the surrounding hills (in a kind of coke piles) because this was easier than transporting masses of wood to Idrija. But then too much mercury got stolen...

Mercury was first exported via Venice to Levante, and later also to Germany and Holland, to be further exported to Mexico and Peru for use in amalgamation in silver and gold mines there. Since 1659 Amsterdam was the main export center. In 1785-1797, up to 700 tons of mercury were exported to Spain yearly.

A castle (now housing the Museum) was erected 450 years ago to protect mercury against possible attacks by the Turks who roamed Europe at that time.

The world use of mercury peaked around 1968. According to the 1968 US data, of the total of 2500 tons, 600 tons were used in chlorine and caustic soda production, 600 tons ended up in batteries and light bulbs, 380 tons in control instrumentation, 360 tons as color additives, 141 tons in people's teeth, 120 tons in agricultural fungicides, 13 tons were used in paper and cellulose industry, etc. Cinnabar is a well known dye; mercury chloride was used as antiseptic even in this century.

The mining operation was a textbook case of full utilization of the wood and water resources in the river Idrijca basin, without actually destroying either, except very close to the smelting operation.

Several water dams for floating timber were built in remote valleys called Klavze (from latin for dam). Starting in 1767, the local engineer Jozef Mrak finished the first Klavze in Bela, Idrija Klavze made of stone in the Belca valley (1769) and in the Idrijca valley (1772), and repaired some others. They had wooden doors that were flung open to produce a rushing wave sweeping the valley below and carrying the year's lot of timber towards Idrija. Timber was collected in the town by wooden combs across the river, the first of these having been constructed in 1531.

The mine was drained by several water-driven pumps. Restored in 1994 is the largest still existing water wheel in Europe: popularly called Kamst (from German, Kunst, for art), 13.5 meters in diameter, built around 1790, and driven by water from the Idrijca river, it was pumping water from from a depth of up to 300 meters without interruption for 160 years, until 1948, after the WWII! Already in 1665 the Englishman Walter Pope wrote he had never seen water wheels as large as those used in Idrija.

In the 16th century, Paracelsus visited Idrija and introduced mercury in medicine. Joannes Antonius Scopoli served as medical doctor in Idrija from 1745 to 1769. (1761 is the year of the first lace and of the work by Scopoli: De Hydrargyro Idriensi, Idrija De Hydrargyro Idriensi.) Balthasar Hacquet, who also wrote the Oryctographia Carniolica and corresponded with Carl Linnaeus, lived in Idrija from 1766 to 1773; at that time, Idrija was the second largest town in Carniola.

The riddle of the Idrija ore deposit (its origin and structure) was fully solved only after WWII by Ivan Mlakar, who in doing so established the internationally acclaimed Idrija geological school.

Points of Interest

One can do all the following in the order listed.

The Church of the Holy Trinity, on the spot where, according to tradition, mercury was first discovered by a tub-maker.

Right below are the Town hall (1898) and the first non-classical secondary school (realka, 1901) in Slovenia.

The Gewerkenegg castle (Municipal Museum), housing also the memorial rooms of the writer France Bevk and the politician Dr. Ales Bebler (among other things, a letter from Mr. Dulles is there). There is a permanent exhibition of about a hundred works of art donated by Mrs. Mazza, a native of Idrija and owner of an art gallery in Rome, Italy.

The old town square is dominated by the Old Wheat Magazine, now housing a public library, gallery and furniture salon, next to Slovenia's first theatre house, the Forestry Administration building, and the former presbytery.

Anthony's shaft (1500) is the second oldest preserved mine entrance in Europe (you enter the level tunnel through a house and a chapel).

Kamst, on the other side of the town, is now open to the public.

A tranquil walk above the Idrijca river, along the Rake (an open water canal for driving the Kamst, nowadays after 400 years still supplying water for an electrical power plant) built in 1596, brings one to the dam feeding the Rake, and then to Divje jezero (Wild Lake), a siphon-driven (86 meters deep) little lake half enclosed by 200 meters high vertical cliffs.

Bela, about 8 km upstream of Idrija, is a jewel of almost unspoiled nature, a bathing and picnicking place at the confluence of the Idrijca and Bela rivers. A removable dam creates a pool with warm but fresh stream water.

Still upstream, in both Bela and Idrijca valleys, an old, winding Italian military road brings you to Klavze (Slovene pyramids).

From the Bela Klavze you can proceed to Vojsko, the highest-lying village in Slovenia. From the Vojsko Plain, you can descend into a remote valley with the WWII Slovenija printing office (with equipment smuggled from Milan, Italy, during the war), which printed Partizanski dnevnik (Partisan Daily), the only newspaper published by Resistance movements in Europe. (The place was chosen by my grand-grand father.)

A Lace-makers' Festival is held in Idrija in summer. The main event in the festival is a competition usually entered by a couple of hundred women (no age limit), and even a few men.

In the Nebesa (Heavens) restaurant, or in the Pri Skafarju (At the Tub-maker's) inn you can taste the traditional miners' food, zlikrofi (potato balls with marjoram and other spices, wrapped in thin dough, and cooked). Beware: I've never seen zlikrofi prepared properly anywhere else in Slovenia.

The Municipal Museum is open 9 am to 6 pm every day; phone: +386 5 3726 600. Visits to the mine as well as other points of interest can be arranged through the Museum.

(C) 2000-2007 Rajmund Krivec
Version 2 (2007). From various sources, with thanks to Darko Viler.