Grube Rosenhof — Schacht Ottiliae Clausthal-Zellerfeld · Niedersachsen · Germany

The Rosenhöfer Gangzug, a vein system west of Clausthal at the western edge of the Oberharzer plateau, was the mineralised basis of the Grube Rosenhof and its predecessors. Mining on the vein began by the middle of the sixteenth century, with the bergmännische Bergfreiheit granted for Zellerfeld in 1554. The earliest independent collieries on the vein were Sankt Anna, Drei Brüder, Thurmhof and Rosenhof, all of which came rapidly into productive operation because of rich ore bodies. Schacht Sankt Anna was active from 1552. Drainage of the workings required early investment in adits: from 1554 the Fürstenstollen was driven, and from 1570 the Rabenstollen was advanced, beginning in the Rabental at Frankenscharrnhütte. By about 1591 the collieries appear on a documented Bergzettel. In 1649 a fire caused by negligence of a Kunstwärter destroyed the main shaft.

Around 1600 the two workings Thurmhof and Rosenhof consolidated to form the new Grube Thurm-Rosenhof. Alongside it continued the Gruben Sankt Anna, Drei Brüder, Himmlisch Heer and Alter Segen. During the seventeenth century additional mines came into being: Heilige Drei Könige, Sankt Johannes and Braune Lilie. The Grube Alter Segen sank a second shaft, the Liegender Alter Segen, and Grube Thurm-Rosenhof received a new shaft — the Unterer Thurm-Rosenhof — while the earlier working was renamed Oberer Thurm-Rosenhof. The round Radstube (water-wheel chamber) associated with this mine was originally an above-ground structure approximately 10.50 metres in diameter. As the adjacent spoil heap grew over the centuries, a protective ring wall was added and progressively heightened, eventually reaching 24 metres, so that what had been a surface building became effectively an underground structure.

From 1799 the Tiefe Georg-Stollen, completed within 22 years of its commencement, took over the drainage of all the Rosenhöfer Revier mines, providing a drainage level approximately 250 metres below surface. As drainage improved and the workings deepened, the independent mines continued to consolidate. By the early nineteenth century only three mines remained active on the Rosenhöfer Gangzug: Neu-Thurm-Rosenhof (which had absorbed the Schächte Braune Lilie, Zilla and Sankt Johannes), Alter Segen (with Schacht Drei Könige), and Silbersegen (which had taken over the Schacht Himmlisch Heer and sunk the new seigerer Silbersegener Schacht as the first vertical shaft on the Rosenhöfer Gangzug). This seigerer shaft was designed as the new central hoisting shaft for the revier. The water-wheel chambers continued to house the large Kehrrad that drove the man-riding Fahrkunst; the existing Kehrrad was installed in 1840, and wooden parts of a later Kehrrad built in 1897 and in use until 1909 were recovered during excavations.

In 1864 the Ernst-August-Stollen broke through the workings, superseding the Tiefe Georg-Stollen as the principal drainage adit and providing a new drainage level approximately 330 metres below the Ottiliae-Schacht collar. In 1868 sinking began in the country rock on a new vertical shaft, the Ottiliae-Schacht, named after the Prussian Berghauptmann Ernst Hermann Ottiliae (1821–1904). In October 1878 a severe accident occurred in the Schacht Unterer Thurm-Rosenhof: the Fahrkunst broke at a depth of 345 metres, killing eleven miners and seriously injuring twenty more. The repaired installation continued in use into the 1920s.

In the final phase of the Oberharz ore industry the mine, now known as Grube Rosenhof, absorbed the Gruben Silbersegen and Alter Segen. In 1905 the underground Thekla-Schacht was created as the new winding shaft, replacing the Unterer Thurm-Rosenhof, which was thereafter abandoned. From 1905 the Ottiliae-Schacht, connected to the Tiefste Wasserstrecke, became the central hoisting shaft for the Rosenhöfer, Zellerfelder and Burgstätter Gangzüge, reaching its final depth of 594 metres after comprehensive modernisation between 1900 and 1905 including conversion to electric Koepe winding. The greatest depth achieved across the Grube Rosenhof was 697.4 metres. The mine's power water was supplied through several installations of the Oberharzer Wasserregal, principally the Oberer and Unterer Rosenhöfer Fall and the Bremerhöher Graben.

In 1930 the Grube Rosenhof and all other mines around Clausthal-Zellerfeld were closed, the direct consequence of the global economic depression and its effect on metal prices, combined with the high cost of production in these ageing deep mines. After closure the mine workings were progressively filled; by 1930 the round Radstube was also filled in. The structure was rediscovered by chance around the turn of the millennium and subsequently excavated. From 1990 the Oberharzer Geschichts- und Museumsverein began research and clearance work; the round Radstube has been accessible since 2005 in the framework of guided tours run by the Oberharzer Bergwerksmuseum in Clausthal-Zellerfeld. The oval Radstube, from the early nineteenth century and 15 metres high, is also accessible by underground tours. The Grube Rosenhof is listed on the Welterbe-Route of the UNESCO World Heritage designation Bergwerk Rammelsberg, Altstadt von Goslar und Oberharzer Wasserwirtschaft, which was extended in 2010 to include the Oberharzer Wasserwirtschaft. Visits to the Rosenhöfer Radstuben are possible as an outstation of the Oberharzer Bergwerksmuseum.