Active former potash site at Sondershausen housing the Erlebnisbergwerk visitor mine, rock salt extraction, and underground waste disposal under GSES GmbH.
The Kaliwerk Glückauf Sondershausen, founded in 1893 in the Fürstentum Schwarzburg-Sondershausen, is the oldest still-accessible potash mine in the world and is considered the eleventh German potash colliery. Sinking of the first shaft, the Brügmannschacht, began on 1 May 1893 and the site produced potash from 1896 until 1991, raising a total of 110 million tonnes of raw salt over 95 years. The works expanded to six shafts named after prominent figures of the enterprise; the Petersenschacht (Schacht II) with its 44-metre Jugendstil headframe modelled on the Eiffel Tower is today one of the landmarks of the city.
Schacht V, the Dr.-Esser-Schacht with a depth of 752 metres and a 47-metre headframe, received a new headframe in 2018. After the close of potash production in 1991 the Glückauf Sondershausen Entwicklungs- und Sicherungsgesellschaft mbH (GSES GmbH) was established in 1995; the site now operates as a visitor mine, produces rock salt for road gritting, and accepts underground waste disposal.
The discovery of potash potential at Sondershausen began on 13 March 1891 when the entrepreneur Heinrich Leonhard Brügmann, a trained mine surveyor from Brünninghausen bei Dortmund, applied to the princely Landrat Henniger in Sondershausen for a prospecting licence. The licence was granted on 15 June 1891 and the first exploratory bore began on 1 August of that year in a 2.7-hectare field at the so-called Gänsespitze near Jecha. On 1 December 1891 the bore encountered a rock salt layer about 10 metres thick at 465.2 metres depth; six months later a 25-metre carnallite seam — the Kaliflöz Staßfurt — was intersected at 616 metres. A second bore in May 1892 confirmed the commercial grade of the potash deposit.
At that period the Kingdom of Prussia held what amounted to a potash monopoly and operated the Schutzbohrgemeinschaft to resist the opening of new private enterprises beyond Prussian territory. After prolonged negotiation, a unique compromise was reached: Brügmann was permitted to develop one works, the eleventh in Germany, but no further independent enterprises would be allowed in the Fürstentum. In return he received the exclusive potash rights for 519 square kilometres — a field large enough in principle for twenty-five large mines. The purchase price agreed was an annual Grubengefälle of 40,000 Mark and 15 per cent of net profits in perpetuity. On 9 February 1893 Brügmann and the Cologne bank A. Schaaffhausenscher Bankverein founded the Gewerkschaft Glückauf-Sondershausen. Total investment up to full production in 1898 amounted to 4,976,094.14 Mark. Brügmann himself did not live to see production begin; he died of influenza in Cologne on 10 December 1893. The first shaft was named the Brügmannschacht in his honour.
Sinking of the Brügmannschacht began on 1 May 1893 between the villages of Stockhausen and Großfurra, close to the Erfurt-Nordhausen railway line and on the bank of the Wipper. At 634 metres the shaft intersected a 14-metre potash seam of sylvite, halite, and anhydrite. Potash production began in 1896 with an output of 32,100 tonnes, initially despatched unground. Following the completion of the Chlorkaliumfabrik, the first consignment of potassium chloride fertiliser left the Sondershausen works on 24 February 1898. On 1 March 1898 the Gewerkschaft became a full member of the Deutsches Kalisyndikat with provisional production quotas.
The quota regime of the Syndikat was persistently unfavourable to the works. In the first period the enterprise received only 55 per cent of the average syndikat quota; only after sustained protest was this raised to about 70 per cent in the third period (1902–1904). In 1910 Kaiser Wilhelm II enacted the first Reichskaligesetz, which regulated sales and prevented the formation of new works; this had a beneficial effect on quota allocation for Sondershausen.
To obtain improved quotas, Schwarzburg-Sondershäuser Staatsminister Hermann Petersen championed the sinking of a second shaft. In October 1909 the Petersenschacht (Schacht II) was completed at 790 metres depth near the main railway station and the village of Bebra. Since the works stood at the entrance to the residenz city, the prince insisted on architecturally distinguished design. The resulting composition of traditional building forms and industrial architecture embodies Jugendstil principles; the 44-metre headframe, modelled at princely request on the Paris Eiffel Tower, is today regarded as one of the landmarks of the city alongside the Residenzschloss. The shaft was named Petersenschacht in honour of Staatsminister Petersen. Schacht II was among the first four second-shafts to be sunk in the German potash industry.
In the following years the Glückauf group expanded through daughter companies, exploiting a contractual loophole that allowed the creation of separate gewerkschaften with their own quotas. By 5 April 1909 five gewerkschaften existed: Glückauf-Sondershausen (22.7 per cent of total area), Glückauf-Bebra (8.2 per cent), Glückauf-Ost (14.4 per cent), Glückauf-Ebeleben (20.2 per cent), and Glückauf-West (21.3 per cent). By 1914 shafts III through VI had been sunk, each named after a chairman of the Grubenvorstand. The Müserschacht (Schacht III, 655 metres, 1911/1912) belonged to the Gewerkschaft Glückauf-Berka. The Raudeschacht (Schacht IV, 746 metres, 1911–1913) belonged to Glückauf-Ost. The Dr.-Esser-Schacht (Schacht V, 752 metres, 1912/1913) and the von-Nesse-Schacht (Schacht VI, 615 metres, 1912–1914) also belonged to Glückauf-Ost. By 1914 the Glückauf group ranked tenth among the 29 companies that produced 82 per cent of German potash.
The First World War brought severe operational constraints. Export ceased, production fell, and many workers were conscripted. Shafts I, III, V, and VI were temporarily closed; only the Brügmannschacht and Raudeschacht remained intermittently in production.
From early 1922 the Wintershall-Konzern moved to acquire the Glückauf group through its financing vehicle Kali-Industrie AG. On 20 September 1926 the Sondershäuser Gewerkenversammlung resolved on liquidation of the enterprise, bringing the 34-year-old independent Gewerkschaft to an end by absorption into the Wintershall-Konzern.
The site grew to become the principal Kalikombinat of the DDR, and by 1989 alone the mine raised 2,300,000 tonnes of raw salt. At the time of the closure of potash production in 1991 approximately 3,000 people were employed at the Sondershausen location. Over its entire potash-producing life from 1896 to 1991 the works raised a total of 110 million tonnes.
From 1991 to 2002 voids beneath the town of Sondershausen and the village of Großfurra were backfilled to stabilise the old workings. In 1995 the Glückauf Sondershausen Entwicklungs- und Sicherungsgesellschaft mbH (GSES GmbH) was established as the privatised successor entity. Since 2006 approximately 200,000 tonnes of rock salt are extracted annually for road gritting. In 2018 the headframe of the Esserschacht (Schacht V) was replaced with a new structure. The site operates as the Erlebnisbergwerk Glückauf for visitor tours and continues to provide underground waste disposal services for industrial residues.