A bike ride back in time: Freiberg’s historical mining sites

Dear readers,

I am Rosie and, as part of the SULTAN project, I am based at the Helmholtz Institute Freiberg for Resource Technology in Freiberg, Germany. My work here involves geometallurgical studies, characterisation and modelling of tailings deposits in the Freiberg region.

Freiberg, located in the Erzgebirge (the ‘Ore Mountains’) in Saxony, has a very rich history of mining and smelting, particularly for silver. In the central Freiberg mining district, more than 5000 tonnes of silver were produced from the 12^th to the 19^th century. Both indium and germanium were first discovered in the Freiberg district in the 19^th Century (Reich and Richter 1863a, b, 1864; Winkler 1886), and are now regarded as critical or strategic metals by the European Commission.

On a beautiful sunny day, I went on a bike ride around some of the old mine working and mining waste deposits near Freiberg. This was the perfect way to learn about the significant local mining history, and see the rich legacy that this mining has left behind. Over twenty kilometers later, and after many (too many) hills, I arrived home somewhat tired, but excited to share what I learnt.

Firstly, a brief history of mining in the Freiberg District

Mining in Freiberg was fairly continuous from 1168 to 1969.  Early on, due to technological limitations, the ore was mined to a depth of only 15 m. Over the next few hundred years, deeper underground mines and larger open pit mines were developed. However, as depth of mining increased, groundwater became a problem and mining decreased. A stage of capital investment in the mining industry enabled the groundwater problems to be solved, and mining then continued.

During the 30-year (1618-1648) and 7-year (1756-1762) wars, many mining and smelting works being destroyed. In order to restore silver mining in the Freiberg district to its former glory, the Bergakademie Freiberg (Freiberg Mining Academy) was founded in 1765, which still exists as Technische Universitat Bergakademie Freiberg (TUBAF) today.

In 1871, gold replaced silver as the dominant coin material and so, again, silver mining suffered. In 1886, the Saxon state bought many of the mines in the Freiberg region to modernise them. This was short-lived and mining of silver again stopped in 1913. The final period of mining in Freiberg for lead, zinc and silver began in 1935, for the armament of Germany in the build up to World War II. After the establishment of the German Democratic Republic in 1950, mining was halted in 1969 due to economic and political reasons.

Now, a little bit of geology (feel free to skip this if it’s a bit too complicated!)

The ore historically mined in the Freiberg district comprises a sequence of polymetallic hydrothermal veins, which occur throughout the whole Erzgebirge. There are four main types of mineralisation in the Freiberg district. The Pb-Zn-Cu-Fe-sulphide-quartz stage and Ag-Sb-sulphide-quartz±carbonate stage formed around 280 million years ago. Later Pb-Zn-Cu-(Ag)-sulphide-fluorite-barite-quartz and Ag-Bi-Ni-Co-As-carbonate-quartz stages are of Cretaceous age (146-66 million years) or younger (Baumann 2000; Seifert and Sandmann 2006; Ostendorf et al. 2018).

Traditionally, the Pb-Zn-Cu-Fe-sulphide-quartz assemblage has been called the ‘Kiesig-blendige Bleierzformation’ (kb formation) and the Ag-Sb-sulphide-quartz±carbonate assemblage has been named ‘Edle Braunspatformation’ (eb formation) (Baumann 2000). The silver-sulphide association of the eb formation was the most important source of silver in the Freiberg mining area.

The hydrothermal veins can also be grouped based on four distinct orientations: Stehende Gänge veins orientated N-S and NE-SW; Morgengänge veins orientated NE-SW and E-W; Spatgänge veins orientated E-W and SE-NW; Flache Gänge veins orientated N-S and NW-SE. A handy saying (well, if you understand German) to remember them is: “Steht der Bergmann morgens auf, spat legt er sich flach”, which translates to something along the lines of “When the miner gets up in the morning, he’s late to lay down”. The kb formation is usually Stehende Gänge or Flache Gänge, and the eb formation is usually Spatgänge. This means that when you measure the orientation of some veins, you can already tell which type of vein it is, and which minerals/metals should be present.

Stop 1: At the corner of Wasserturmstraße and Berggasse, ‘Schüppchenberg’

The first stop, at the base of Schüppchenberg (‘Schüppchen hill’), is thought the be the place where silver was first discovered in Freiberg. In the 12^th century, traders from Prague used to travel along the Münzbach stream, which now runs underground at this location. As the story goes, in 1168 some merchants spotted silvery rocks in the tracks from the wagons, so these rocks were sent to Goslar for analysis and the silver was found.

The discovery of the first silver in this area led to the ‘Berggeschrei’, which directly translates as the ’Mining screams’, but means something more like the news of rich ore discoveries spreading quickly by word of mouth and bringing people to the area to mine. The mining master of the area, Markgraf Otto von Wettin, declared the mountain to be ‘free’ and this led to the town of Freiberg (Free Mountain) being established in 1218.

Stop 2: Alte Elisabeth

The second stop on the tour was the historical mine of Alte Elisabeth, which was first mentioned in 1384. The shaft at Alte Elisabeth is inclined (‘tonnlägig’) at around 30°. Around 1511, Alte Elisabeth was mentioned to be the most productive mine in the central Freiberg mining district.

There are many small shafts all over the Freiberg mining district, which were used to access deeper ore, including underneath Freiberg itself. Early on, miners were lowered down by winch systems, which could reach depths of up to 50 m. A reconstruction of a small hut housing one of these small shafts can be seen at Alte Elisabeth.

Another way of accessing the ore was along inclined shafts where the miners wore an Arschleder (directly translated as ‘Arse Leather’, or more politely translated as a ‘Miner’s apron’), to lower themselves down. Nowadays, mining students at TUBAF jump over an Arschleder held by their professors as part of their induction into the university.

Stop 3: Reiche Zeche

The third stop was at the Reiche Zeche mine. Reiche Zeche is now TUBAF’s teaching and research mine, where they work up to depths of around 230 m via a vertical (‘seiger’) shaft. It is also possible to go on guided tours of the mine, to a depth of around 150 m.

Stop 4: Davidschachthalde

The next stop was at Davidschachthalde (‘David shaft tailings’), where fine processing wastes were deposited. The area also served as a slag heap for several mine shafts, with waste rocks predominantly from the kb formation. The nearby Davidschacht (‘David shaft’) was the penultimate shaft to be sunk in the Freiberg mining district, in the middle of the 19^th Century, and reached a depth of 736 m.

Stop 5: Roter Graben

The fifth stop was at the Roter Graben (‘Red Trench’), next to the River Mulde. The Roter Graben was built from 1614 to 1615 and is one of the most important sites of the mining water management in the central part of the Freiberg mining district. The channel collects water flowing out of the mine through adits, which are horizontal tunnels built to drain groundwater from the mines. The name Roter Graben probably derives from the fine, red sludge (which you can see in the photo below) deposited in the channel. This is most likely iron oxides which were deposited from the iron and manganese rich mine water.

 

Stop 6: Alter Tiefer Fürstenstollen

Now cycling along the River Mulde, the sixth stop of the tour was further along the Roter Graben, at the Hauptstollnumbruch adit.

The Alter Tiefer Fürstenstollen, which was first mentioned in 1384, is a network of tunnels with a total length of around 80 km. At this particular entrance to the Alter Tiefer Fürstenstollen, the circulation of air through the mines and tunnels sucks the air in very strongly.

Stop 7: Lorenz Gegentrum

The seventh stop was at Lorenz Gegentrum, another waste rock pile. It mainly consists of hard quartz-galena ore, which was rejected because it was too hard to crush and smelt. Instead, the softer barite-galena ore was favoured as it was easier to extract the metals. This slag heap is now popular with mineral collectors, searching for the rare green pyromorphite and barrel-shaped hydroxyl-apatite.

Stop 8: Münzbachtalhalde

The eighth and final stop was at the Münzbachtalhalde (Münzbach valley tailings deposit), near the village of Halsbrücke. This is the main study site for my PhD, where we will carry out a drilling campaign to gather samples for analysis, characterisation and 3D modelling. Many of the other SULTAN ESRs will also use this material for their research.

The Cu-Zn-Pb tailings were deposited here from 1955-1968, between two dams in the valley of the Münzbach stream (do you remember this stream from earlier? It is the same stream next to which the first silver in Freiberg was discovered, from stop 1). Instead of being diverted, the Münzbach stream goes beneath the tailings in a tunnel, around 320 m in length.

After cycling on to the top of the Münzbachtal tailings, which is now very vegetated and covered in trees, we decided to go down the east dam wall to the base of the tailings. This steep dam is now used by motor cross riders… funny what tailings and waste material can end up being used for!

The end

And so, we reached the end of the bike ride. I hope you have enjoyed learning about the history and legacy of mining in Freiberg as much as I did.

Acknowledgements

I would like to thank my tour guide, Malte Stoltnow, for showing me these sights around Freiberg, and for not getting too annoyed when it took me a long time to understand the old German mining terms, or when I complained about cycling up another hill. Thanks also to the Society of Economic Geology Student Chapter of Freiberg, who run this bike trip every year and collated a lot of the information.

Sources and further information

Freiberg tourist information: http://www.freiberg-service.de/en.html

UNESCO World Heritage Site of the Montanregion Erzgebirge: https://www.montanregion-erzgebirge.de/welterbe//montanlandschaft-freiberg.html

Arschleder: https://en.wikipedia.org/wiki/Miner%27s_apron

Roter Graben: https://de.wikipedia.org/wiki/Roter_Graben_(Erzgebirge)

Dieter Schräber: Mining historical exploration path “Roter Graben”, Freiberg 2006 (http://www.freiberg.de/freiberg/ressourcen.nsf/docname/Ressourcen_5BDE2D7E6A9D34EEC12574480047467F/$File/RtrGrbn.pdf?OpenElement)

Bauer, M. E., Burisch, M., Ostendorf, J., Krause, J., Frenzel, M., Seifert, T., & Gutzmer, J. (2019). Trace element geochemistry of sphalerite in contrasting hydrothermal fluid systems of the Freiberg district, Germany: insights from LA-ICP-MS analysis, near-infrared light microthermometry of sphalerite-hosted fluid inclusions, and sulfur isotope geochemistry. Mineralium Deposita, 54(2), 237-262.

Baumann L, Kuschka E, Seifert T (2000) Lagerstätten des Erzgebirges. Enke im Georg Thieme Verlag, Stuttgart

Burisch M, Hartmann A, BachW, Krolop P, Krause J, Gutzmer J (2018a) Genesis of hydrothermal silver-antimony-sulphide veins of the Bräunsdorf sector as part of the classic Freiberg silver mining district, Germany. Mineral Deposita. https://doi.org/10.1007/s00126- 018-0842-0

Ostendorf J, Henjes-Kunst F, Seifert T, Gutzmer J (2018) Age and genesis of polymetallic veins in the Freiberg district, Erzgebirge, Germany: constraints from radiogenic isotopes. Mineral Deposita. https://doi.org/10.1007/s00126-018-0841-1

Reich F, Richter T (1863a) Ueber das Indium. J Prakt Chem 90:172–176. https://doi.org/10.1002/prac.18630900122

Reich F, Richter T (1863b) Vorläufige Notiz über ein neues Metall. J Prakt Chem 89:441–442. https://doi.org/10.1002/prac.18630890156

Reich F, Richter T (1864) Ueber das Indium (Fortsetzung). J Prakt Chem 92:480–485. https://doi.org/10.1002/prac.18640920180

Seifert T, Sandmann D (2006) Mineralogy and geochemistry of indiumbearing polymetallic vein-type deposits: implications for host minerals from the Freiberg district, eastern Erzgebirge, Germany. Ore Geol Rev 28:1–31. https://doi.org/10.1016/j.oregeorev.2005.04.005

Winkler C (1886) Germanium, Ge, ein neues, nichtmetallisches Element. Ber Dtsch Chem Ges 19:210–211. https://doi.org/10.1002/cber.18860190156