The Schevenhütte quarry is a former slate quarry in Stolberg-Schevenhütte. Unique Schevenhütte natural stone was quarried here presumably from the Middle Ages until 2008. In the 20th century until it was closed down, the quarry was called "Kaspar Müller I Quarry". It is located on the northern edge of the Eifel at the southern end of Schevenhütte. Geologically, it is part of the outermost foothills of the Venn saddle, where very old rocks from the latest Ordovician period are exposed. These rocks are the oldest in North Rhine-Westphalia. As a special feature, the so-called "Schevenhütter Schichten" (Schevenhütte strata) dip very straight in the quarry area and were thus worth mining. "Schevenhütter Naturstein" was quarried mainly in two varieties, a greenish and a red variety. Basically, the stone from the middle and upper Wehebach layers was roughly processed and sold on site. The "Schevenhütter Schiefer" (Schevenhütte Slate) was used in a variety of ways throughout the region, including as ornamental and rough building material, but also as walking slabs and as gravestones.
After the closure in 2008, slates still in stock were sold until the middle of 2012. After this time, the site was left to its own resources. The site was neither renaturalised nor restored nor was the slope stabilised. With the end of the swamping in the quarry basin, an endorheic small lake developed over time and the open quarry slope in the east suffers greatly from the lack of supporting rock, which repeatedly causes rock slides, landslides and mass movements.
Today, the quarry is a registered soil heritage site of the Kupferstadt Stolberg because of its outstanding role as a teaching and research object. The site is owned by Laufenburg GmbH and may not be entered due to the acute danger to life caused by the rock slides. The site is fenced off.
Geological classification Schevenhütte is located in the border area of the Ardennes and the northern Eifel in the valley of the Wehebach, with the Wehebach, as part of the Inde catchment area, draining into the Indemulde to the north. The most prominent part of the Ardennes is the Ardennes anticlinorium with the Rocroi and Stavelot-Venn large saddles. Schevenhütte is located exactly at the north-eastern end of the latter Venn saddle. In the Stavelot-Venn Grand Saddle, there are old rocks. The oldest layers are the Deville layers of the Lower Cambrian, followed by Revin layers of the Middle and Upper Cambrian and then by "Salm" rocks from the lowest Ordovician.
The quarried shales come from "Salm 2" (Sm2), today's Middle and Upper Wehebach strata. This makes the former quarry the site with the oldest exposed rock strata in NRW today. The age is 490 million years, whereby the determination can be made relatively accurately by the fossil of the graptolite species "Dictyonema flabelliforme".
Within the strata of SM2, the quarried siltstone is found in two different predominant forms, which differ mainly in their sandstone content. The greener variety is also called banded shale and is dominated by fine sand- and silt-streaked mudstones, in some of which sandstone beds can be found. Next to it is a redder, more clayey variant without sandstones. The clayey variant increases towards the top and thus the red colouring also becomes stronger. These layers of the Upper Salm occur once more to the south at the headwaters of the Thönbach (a tributary of the Wehebachtalsperre). Thus, the occurrence in this form is limited to the synclinories of the Wehe and the Thönbach. The red colouration of the rock is not completely clarified, although much points to a stronger haematite and manganese oxide content, as solution from the overlying colourful Gedinne layer is no longer considered likely today.
The strata were already deformed during the Kalendonian mountain building in the Silurian and then, clearly visible through tectonic structures, again during the Variscan mountain building in the Carboniferous. The tectonic deformations are particularly well visible along the scarp of the L25 in Schevenhütte, for about 300 m north of the quarry. This rock formation is also a registered archaeological monument. There are mainly north-vergent folds and thrusts dipping to the south. The fold axes run W-E, the slate rock of the Wehebach strata dips S there. The quarry, which is only about 30 metres higher, is clearly less folded. The strata of siltstone and banded schist found here show weak bending of their bedding planes in contrast to the shale-sandstone sequences along the road.
Along the eastern slope of the Wehetal, the bedrock strikes out regularly. Due to the location, the soil formation is not very strong and the cover is thin. Above the edge of the quarry, the soil thickness is at most 30 cm.
Historical context
Historical origins of the area The Wehe area was settled and mined at the latest in Roman times, probably even earlier. The Wenau monastery was founded as early as 1122. The name shows that the Wehe was already in use at that time. Iron was probably mined in the area of the Rote and Weiße Wehe to the south of Schevenhütte as early as pre-Roman times, but certainly in Roman times. In addition, an old Roman road coming from Kornelimünster ran through Schevenhütte, up through the Wehe valley to the Rennweg in the direction of Düren, which still exists today. The end of the Roman period also marked the end of iron processing for the time being. It was rekindled by the copper masters, who settled in rows along the Wehe. During this period, charcoal burning was also very strong and the slopes of the Wehe valley were almost completely cleared. In Schevenhütte the conditions were very good due to the water power of the Wehe stream, the forests of the Eifel and the ore and stone deposits. Industry did not come to a standstill until the middle of the 19th century.Tristan Lothmann: . Eine Untersuchung mittels historischer Daten und LIDAR DGM. RWTH-Aachen, Aachen 2020.
History of the site On the Tranchot Map, the map of the Rhineland drawn by the French around 1805, a quarry operation can already be seen at the present location. The inscription on the map is definitely wrong, as the Wittberg lies much further north, but the other localities are correct. The quarry is not to be seen on the Prussian original map, but this is also somewhat less informative in terms of quality. On the new Prussian map and the 1936-1945 TK25 the quarry is clearly visible.
The leasing and use of the quarry during the period of more than 200 years is not completely clear.
It is certain that the quarry was used to procure building materials for the forester's lodge (today Nideggenerstraße 99) near Helenasruh, which was built in 1852. Until the end of the 19th century, the quarry consisted of two smaller quarries. With the construction of the parish church in Schevenhütte around 1890, so much material was quarried that the separating rock bar disappeared and the site could be operated as a single quarry. There is evidence from 1894 of the extraction of large stone slabs in the operation of a local stonemason by the parish priest of Schevenhütte; around the turn of the century a new tenant operated the quarry with two men-servants and two horses each. There is evidence that the quarried slabs were delivered as far away as Aachen Rothe Erde. In 1911, the Stolberg entrepreneur Hans Prym bought the surrounding forest and with it the property of the quarry. Until the First World War, slabs for pavements and the like continued to be exported to the surrounding area of Aachen. After the war, the quarry was dormant until about 1935, when Prym found a new tenant. He employed up to 15 workers. The overburden from the quarry was used by pioneers as a substructure for the road to Düren as part of the construction of the Westwall. Due to a lack of work, quarrying came to a standstill again around 1940.
The course and ownership of the quarry after the Second World War are also unclear. Kaspar Müller presumably took over the quarry operations around the 1950s. From then on, the operation also bore the name "Kaspar Müller I Quarry". At the beginning of the 1980s, he finally bought the quarry site from Laufenburg GmbH. In the 1960s, up to 60 employees were employed and 600-900 t of material were quarried per month; in the 1950s, there were still only about 30 employees and 400-450 t. Quarrying became more and more motorised and the demands on the products also changed several times over the years (see below), but on 30 June 2008 active operations ended at the Kaspar Müller I quarry. The stockpile of stone slabs continued until August 2011. With the cessation of work, the mucking measures in the quarry basin also ended. the site was not left in an orderly manner. The buildings were left unchanged, and the site was neither renaturalised nor secured against rockfalls.
Efforts for other quarry operations In the 1950s, a new quarry site, Steinbruch Kaspar Müller II, was developed in order to gain greater independence from the lease of the parent quarry. Due to poor rock properties, the quarry never became economically viable and mining ceased again a few years later. Due to the Wehebachtalsperre, the area at the former confluence of the Rote and Weiße Wehe is now in the flood zone.
Another attempt at expansion occurred around the same time near the present-day water treatment of the Wehebachtalsperre in the form of the Schwontzen quarry. Here, too, both the uneconomical nature and the insufficient rock quality led to its swift abandonment.
Operation of the quarry
Quarried rocks
Primarily two varieties of ornamental rock were mined and processed. Even if the lithological description and naming is not quite clean, the commonly used names are given. The grey-green fibrous siltstone is popularly called "Tonschiefer" (clay shale); the red-purple one is called Bänderschiefer (banded shale).
The predominant variety of exposed siltstone is the grey-green to bluish clay-banded siltstone. As described, these rocks are among the oldest in North Rhine-Westphalia and were formerly placed in the Salm 2, although they are more likely to be placed in the lower Salm due to a find of Dictyonema flabelliforme. In various literature these layers are also described as Wehebach layers. The layers in the quarry are relatively little folded, which made quarrying economical.
In the prominent east wall, the clay shales and the banded shales are recognisable with occasional benched sandstones. These sandstone beds can be classified as turbidites, as they partly carry ripple bedding and convolute bedding structures. They have a high carbonate content, which produces the dark brown discolouration during weathering.
Clay slate The Tonschiefer from the lower Salm (Wehebach layers) is a clay-banded siltstone with a grey-greenish colour. (Walter 2010) The layers of the clay shale are mostly deeper than the banded shale, are much better sorted and partly carry sandstone beds in the rock.
Banded shale The reddish-purple, more clayey Bänderschiefer without sandy parts tends to be exposed in the upper layers. The red colour is due to an increased manganese oxide and haematite content, which in turn were caused by submarine volcanic ejections and could sediment particularly well at this location. Individual layers of fine sand wedge out of the banded shales, creating a characteristic flashlayer. This can be seen as graded fine stratification on the surfaces of the rocks (see pictures). A very dense bioturbation prevails. Sedimentation of the ribbon shale occurred on a shallow marine delta platform.
Mining methods