History
The potash deposits beneath Neuhof were located through exploration boreholes from 1900, revealing a Werra-Formation Zechstein seam extending approximately 15 kilometres north to south and 8 kilometres east to west, with a seam thickness of about 2.5 metres and potassium chloride content meeting or exceeding that required for Kainit. The absence of the normally problematic Plattendolomit gave confidence that shaft-sinking could proceed without excessive water difficulties — a confidence that proved unfounded.
The Betriebsplan was approved on 19 December 1905 and sinking of the Schacht Wilhelm von Recklinghausen began on 8 January 1906. The shaft diameter was 5.80 metres internal clear width. At 17 metres depth, considerable water inflows from the Buntsandstein were already measurable; by 70 metres they reached 5 cubic metres per minute. Steam pumps proved inadequate — their plunger mechanisms were destroyed by sharp quartz sand carried in the water — and high-pressure centrifugal pumps were substituted. At 112 metres depth, a motor failure caused the shaft to flood completely with an inflow of 12 cubic metres per minute. Cast-iron tubbing (Tübbings) was used throughout the water-bearing strata from 16.5 metres downward; the first wedge ring (Keilkranz) was placed at 16.5 metres. The total cost of the shaft reached 9 million Goldmark by completion. On 10 February 1906 the mine was entered in the land register under the name Gewerkschaft des Bergwerks Siegel II; the 99 Kuxe of Fedor Siegel were subsequently transferred to Emil Sauer, and the Gewerkenversammlung renamed the enterprise the Gewerkschaft Neuhof, Kaliwerke zu Neuhof-Fulda.
Sinking was complete in 1909 and underground development works began immediately. A main fan (Hauptgrubenlüfter) was installed and a Wetterscheider built into the shaft to separate intake from return air. In 1910 the surface plant was completed with a maximum processing capacity of 800 tonnes per day: a Rohsalzmühle with two systems each of 70 tonnes per hour, a 1,500-tonne raw salt shed with mechanical filling, two wagon-loading facilities of 75 tonnes per hour, and a 2.5-kilometre Werkanschlussbahn to the Bahnhof Neuhof on the Frankfurt–Göttingen main line. The abteuf frame was converted to a Doppelbockfördergerüst and the hoisting machine was upgraded. First products were dispatched in 1910 with a workforce of 220; the first business year closed with a clear profit. The Gewerkschaft Neuhof was admitted to the Kali-Syndikat with a quota of 11.46 Tausendstel.
The regulatory Zweischachtverordnung required a second mine access: the costs of sinking a new shaft were to be shared with the Gewerkschaft Ellers, which was founded on 11 April 1910 by the separation of 14,226 square metres of the Neuhof concession. The Schacht Neuhof supplied electricity to the Schacht Ellers site and allowed the use of its processing plant and railway. The underground connection between the two shafts was achieved by breakthrough in October 1920 at approximately 533 metres depth.
Following the imposition of the Stillegungsverordnung and the severe disruption of the German potash market after 1920, the mine was placed in standby (Stillegung) at the end of June 1926 by order of the Wintershall AG Generaldirektor August Rosterg. The wartime requisitioning via the Schacht Ellers for the Schakal tank-transmission project under the Organisation Todt in 1944–1945 also affected operations at Schacht Neuhof. After the war, Allied authorities initially considered flooding the shafts; from 1946 munitions stored underground were cleared by the STEG. The mine was returned to the Wintershall AG in 1952.
In 1953–1954 the entire underground and surface installation was rebuilt, and during this reconstruction Schacht Neuhof was deepened to 602 metres. Production resumed in 1954. In 1974 the Kaliwerk Neuhof-Ellers commissioned the world's first ESTA (electrostatic raw-salt separation) plant. In 1995 the 100-millionth tonne of raw salt was raised from Schacht Neuhof. The mine was incorporated into the Kali und Salz GmbH on 1 July 1970 and subsequently into the K+S group. Daily hoisting capacity of the Schacht Neuhof stands at approximately 12,500 tonnes of raw salt. The mine's spoil heap, the Rückstandshalde, is locally known as the Monte Kali and hosts the annual concert series music on top.