Former potash colliery at Sollstedt with its headframe, winding house, pithead baths, and miners' railway station surviving as an accessible industrial heritage site.
The Kalibergwerk Sollstedt was the founding mine of a cluster of potash enterprises in the Grafschaft Hohenstein at the southern edge of the Harz. Shaft sinking began in early October 1902 and was completed in June 1904 after five exploratory boreholes had confirmed the presence of hard salt and carnallite seams at approximately 680 metres depth. The Gewerkschaft Sollstedt was registered at Bleicherode on 15 July 1908, with ownership divided equally between the Kaliwerke Aschersleben and the International Agricultural Corporation of New York.
The underground workings were made continuous with the adjacent Schacht Neu-Sollstedt, satisfying the two-shaft regulatory requirement. Processing of raw salt from both mines was carried out at the Sollstedt mill and factory. After the DDR-era reorganisation the mine operated as part of the Kombinat Kali until potash production was discontinued in 1990.
The mine was subsequently used for industrial waste disposal by backfilling with halite. The surviving surface complex north of Sollstedt includes the headframe, winding house, pithead baths building, the miners' railway station, and a salt-storage building.
The site of the Kalibergwerk Sollstedt lies in the Friedetal, a valley north of the village of Sollstedt in the district of Nordhausen, Thüringen. The geological deposit consists of two seams: a hard salt (Hartsalz) layer 3 to 6 metres thick with an average potassium content of 16 per cent, and a carnallite layer up to 24 metres thick with an average of 10 per cent potassium.
Exploration began with five boreholes, designated Victoria I through Victoria III, Königin Wilhelmine, and Königin Emma. Victoria I found potash-bearing horizons from 680.40 to 705.20 metres; Victoria III from 665.20 to 670.70 metres; Victoria II from 544.80 to 550.50 metres; Königin Emma from 616.30 to 626.60 metres. Königin Wilhelmine showed similar geology to Victoria II but was abandoned for technical reasons before reaching the deposit.
Shaft sinking began in early October 1902 and was completed in late June 1904. The Gewerkschaft Sollstedt was registered at the Handelsgericht Bleicherode on 15 July 1908. The 100 Kuxe were divided equally between the Kaliwerke Aschersleben (50 Kuxe) and the International Agricultural Corporation of New York (50 Kuxe). A 6,000,000 Mark bond at five per cent, repayable at 103 per cent, was issued; the first quotation in Berlin on 15 July 1912 stood at 101.75 per cent.
The Kaliwerke Sollstedt joined the Deutsches Kalisyndikat. The surface buildings constructed during the development phase included a headframe with winding house, a steam boiler plant, a water supply installation with bored well and elevated tank, an office and pithead baths building, workshops and magazine, a gatekeeper's lodge, and a Drahtseilbahn (aerial ropeway) connecting the shaft to the mill at Sollstedt where the raw salt was ground and processed. Electrical power was supplied by the Überlandzentrale Südharz-Bleicherode.
The two-shaft regulatory requirement was met by an underground connection between the Sollstedt shaft and the shaft of the neighbouring Gewerkschaft Neu-Sollstedt. Under a separate contract, Sollstedt also ground and processed the raw salt from Neu-Sollstedt.
In 1910 a portion of the Sollstedt concession area, 13,578,255 square metres, was detached to form the new Gewerkschaft Craja, reducing the original Sollstedt area from 38,216,095 to 24,637,840 square metres. The Kaliwerke Sollstedt held all 100 Kuxe of the Craja concern.
During the First World War production and revenues fluctuated sharply. Annual Ausbeute (distribution to shareholders) rose from 400,000 Mark in the war years to 3,000,000 Mark in 1919 and 2,500,000 Mark in 1920, reflecting post-war fertiliser demand.
As part of the broader DDR-era consolidation of the Südharz potash industry, the mine was operated within the Kombinat Kali structure. In the post-war period the Kaliwerk Bleicherode and the Kaliwerk Sollstedt were linked underground, with both Gruben connected since 1953.
Potash production was discontinued at Sollstedt in 1990, following the collapse of East European markets and the inability to adapt to market conditions. According to the Bergmannsverein Erfurt, the mine then came under an Entsorgungsgesellschaft for underground industrial waste disposal using halite backfill, a use that continued under private operation.
A centenary celebration for 100 years of potash mining in Sollstedt was held on 21 September 2002, at which a commemorative stone was unveiled on the shaft site. A new motorway bridge on the A38 was subsequently constructed over the Friedetal and passes directly over the shaft site, with the headframe visible from the motorway. The surface complex as documented around 2000 comprised the headframe, the winding house and machine room, the pithead baths building, the former miners' railway station (Zechenbahnhof), and the salt-storage building. The mine's underground workings continued to be used for industrial backfilling with halite under the post-closure operator.