Eisenbergwerk Herznach

Useful Information

Location: Bergwerkstrasse 36, CH-5027 Herznach.
(47.473897, 8.042453)
Open: APR to OCT 1st Sun 13-17.
Light: LightIncandescent Electric Light System
Dimension: L=32 km.
Guided tours:  
Bibliography: Geri Hirt (2020): Bergwerk Herznach – Zeitzeuge und Kulturgut, Aargovia 2020 Jahrbuch der hist. Gesellschaft Aargau. pdf
Address: Eisenbergwerk Herznach, Bergwerkstrasse 36, CH-5027 Herznach, Tel: +41-62-878-15-11. E-mail:
As far as we know this information was accurate when it was published (see years in brackets), but may have changed since then.
Please check rates and details directly with the companies in question if you need more recent info.


1207 first written mention of iron mining in Frickental.
18th century mining reduced.
19th century end of mining.
1920 trial tunnel with a length of 30 m dug.
1937 beginn of mining.
1941 Jura-Bergwerke AG founded.
1967 mine closed.
2004 Verein Eisen und Bergwerke (VEB) founded.
2016 show mine opened to the public.
2023 special exhibition about calcite.


The Mesozoic basins of Europe have typically 4 to 5 km of more or less horizontal sedimentary rocks. During the late Dogger, the middle Jurassic, iron ore was produced by submarine hydrothermal springs and wide areas have massive layers of oolithic limestone with a high iron oxide content. The ore has typically about 30 % iron and was mined in the Swabian Alb, in Luxembourg, and in Lorraine, as well as here.

The iron ore was sometimes subject to erosion, and as the limestone is rather easily dissolved, this led to the formation of Bohnerz (pisolitic iron ore). There were also small pits for this very young iron ore, which was of better quality as the limestone was removed, but the deposits were quite small and thus not very profitable.


The Eisenbergwerk Herznach (Herznach Iron Mine) was operated only 30 years, beginning two years before World War II and into the late 1960s. The iron ore production was of national importance as a raw material and being the largest employer was of economic significance for the region. The modern mine was operated by the Jura-Bergwerke AG. The modern iron mining was actually a result of World War I, which made iron ore an important and rare resource, and from 1918 Switzerland tried to exploit national iron ores. They made a first 30 m long exploration tunnel in 1920 which showed a 2 m thick seam of iron ore. But it took many years until finally the mine was opened. The highest production of iron ore was during World War II. The ore was transported to Basel by lorries, and then shipped to the Ruhrgebiet. In other words Switzerland traded iron ore for weapon production in Germany, in exchange for crude steel and other urgently needed goods such as hard coal. But the mining was actually of limited profitability as the iron content of the ore is only between 28 amd 32 %.

The show mine is the result of a local initiative, about 200 locals founded the non-profit association Verein Eisen und Bergwerke (VEB) in 2004 with the goal to make people more aware of the history of ore mining in the upper Fricktal. The started to make the mine safe for visitors and opened the first section of 150 m mine tunnel to the public, Further expansion is in the planning stage. The site is intended to inform people about the geology and the landscape. Highlights are the Bergwerksilo, a huge concrete storage, once held 1000 tons of iron ore. The visitors are transported from the silo to th tunnel with an electric mine train.

The iron ore was already mined during the Middle Ages, but only in open casts. It was smelted locally in furnaces, and mining and smelting left numerous traces in the villages of Wölflinswil and Herznach. In the parish church of Wölflinswil, a sculpture of St. Barbara, patron saint of miners can be seen. Field names such as Blauerai indicate the existence of Blaje (smelting furnaces). Archaeological excavations in the centre of the village of Wölflinswil have also revealed iron-smelting slag. Smelting required enormous quantities of charcoal, the need for wood led to overexploitation of the forests. Every ton of iron goods ready for sale could consume up to 20 tonnes of wood.

As a result of all these mining-related sites, the association also created a mining trail from Wölflinswil to Herznach and on to Zeihen. Former pits, in German called Pinge, are clearly recognizable in the Junkholz area as crater-like depressions. Information boards provide an insight not only into the hard work of the miners in those days, but also explain the complex Jurassic geology in this area. The brochure Eisenweg und Bergwerk Herznach by geologist Peter Diebold and historian Linus Hüsser delves into both the geological and historical aspects of mining in the upper Fricktal.

The sedimentary rock formed at the bottom of an oxygene rich sea, and contains numerous fossils. But the floor of the main tunnel has a spectacular geotope. It was obviously a depression on the sea floor, and the shells of dead ammonites were deposited in a massive layer by sea currents. The floor was washed free by mine water from the adit. Today there is a so-called Ammonitenfriedhof (ammonite cemetery), which is a historic term for such rare deposits. It is the reason why the number of visitors increased dramatically.