23 Pernecker gypsum mining:
Gypsum is a very common mineral from the mineral class of " sulfates " (salts of sulfuric acid). It has the chemical composition Ca[SO4]·2H2O and usually develops tabular or prismatic to needle-like crystals , but also granular to massive aggregates .
In general, gypsum is colorless or white. However, it can take on a yellowish, reddish, gray or brown color due to the absorption of foreign ions or admixtures of various kinds ( sand , bitumen , iron).
Gypsum is a chemically formed “sediment” (deposited rock) that deposits like salt when shallow sea basins dry out. Due to the formation of dolines and sinkholes, gypsum deposits are very easy to recognize, even if they are covered with soil on the surface.
After rock salt, gypsum, which is closely linked to it in terms of deposits, is the second most important mining product in the Salzkammergut. Gypsum occurs mainly in the area around Ischl, Goisern and in the Ausseer Land either as a component of the leached salt cap or in the form of independent gypsum sticks, which at a depth of between 30 - 40 m turn into anhydrite, as the anhydrous form of gypsum.
The exploitation of the usable types of rock found in the Salzkammergut was mostly left to private activity. It was subject to the approval of the Oberamt, which demanded a modest rent for it.
This included, above all, the extraction of gypsum, which was openly exposed in many places in the Ischl district and whose mining and processing had reached a remarkable extent at the end of the 18th century. The Salt Office did not put any difficulties in the way of the gypsum ditch and approved it wherever it did not impair salt mining. It also ensured that the dismantling was carried out in an orderly manner and that the necessary precautionary measures were observed. In most cases, the landowners quarried and processed the gypsum themselves, helping many salt workers to earn a worthwhile extra income.
Gypsum quarries initially existed in the vicinity of Ischl in the Schönmanngraben west of Kaltenbach, in Lindau near the Grabenmühle, in the rear Ramsau, in Roith and in the Kiliansgraben under the Jainzenberg, in Sulzbach at the southern foot of the Siriuskogel and in Perneck and Obereck.
In 1824 the gypsum diggers on the Hundskogel dug out of a 30 fathom (57 m) long, old mining tunnel.
In 1828 further gypsum quarries are mentioned on the Hießeben near Hallstatt, in Zlanbach near Steg and in the Strub in the Goiserer Weißenbachtal. In 1832 the Wildenstein Nursing Office was only able to lease six of the eight advertised gypsum quarries. After the upper layers had been exploited, the operation required a great deal of excavation work and was then only little worthwhile.
In 1844, gypsum pits were still in operation in Perneck and in Goisern am Leisling, on Herndlberg and in Wiesleben. Gypsum was also mined at Hütteneck near Goisern, in a deposit discovered in 1839.
In 1839 a rock fall had buried the large gypsum quarry in the Strub in the Goiserer Weißenbachtal. In Wienern am Grundlsee, a large gypsum deposit was discovered in 1844 and leased from the Salzamt in the same year. However, this small mining was quickly stopped because of the unfavorable delivery conditions at the time. However, this deposit has been used again since 1952. To date, the Rigips company has been quarrying around 300,000 tons of raw gypsum per year.
Gypsum, which found good sales in the ground state above all as a fertilizer, was mined in the Ischl area, especially in Perneck. In 1847 the gypsum pits there were already quite exhausted and further quarrying was no longer worthwhile. It was therefore difficult for the Salzamt to find new leaseholders to continue operating the gypsum pits.
In Perneck, gypsum was mined primarily as a side business. The activities were carried out by the farmers themselves and mostly only in the winter months. External workers were used only occasionally. The Kranabitl, Perneck 20 vulgo "Kranerbauer", Gschwandnter, Perneck 14 vulgo "Gschwandtnerbauer" and Schiendorfer families, Perneck 66 vulgo "Schuster" and the Schiendorfer families, Obereck 9, 11 and 16 operated gypsum mining.
In order to get to the gypsum, up to 17 m deep opencast pits were dug and tunnels were driven. The lumpy gypsum rock obtained was delivered to the sal ammoniac factory in Nussdorf near Vienna and on to Hungary. The hacking was crushed into fertilizer in a separate gypsum ram located on the Sulzbach. The stamp mill, driven by an undershot water wheel, was equipped with 9 stamps. The building of the gypsum plant, which was in operation until the turn of the century, was demolished in 1944.
JA Schultes reported in his "Travelling through Upper Austria" published in 1809 about the Ischl gypsum stamping. 'You can see the plaster stamps, which could be better equipped, as the trade in plaster is not insignificant here. One rams 15 - 16 centners (850 - 900 kg) in one day. The hundredweight of red plaster was worth 22 kreuzer in 1802, the blue 23 kreuzer, the white one being the most expensive, and was worth 24 kreuzer. You need the ordinary for fertilizing. The worker who stands by the rams all day long with his mouth bandaged receives 20 kreuzer.”
The gypsum powder from the Pernecker stamp mill was transported to the towns around Lake Attersee by means of ox carts. There it was used as a sought-after mineral fertilizer for clover grass. The teams of oxen needed one day for the outward journey through the Weißenbachtal, and they drove back the next day.
From 1852, the Schiendorfer families from Obereck and Perneck leased the "Mühlleitengrund" property for the purpose of gypsum extraction. At the "upper gypsum lacquer" a tunnel led eastwards into the mountain. This tunnel curved and emerged from the slope about 150 m to the south-east. The two tunnel entrances had a taxiway and were still passable up until the time before the First World War, later they were filled in. In the area of the southern tunnel exit, a landslide can still be clearly seen in the terrain. On the upper, western edge of the terrain of the "Mühlleitengrund" you can still see an extensive, about 5 m deep pinge, which indicates an underground mining chamber.
In addition, gypsum in this area was extracted in two up to 17 m deep cut-and-cover pits (“lower gypsum coatings” at the soccer field and “upper gypsum coatings”). Over the years, the pits have repeatedly flooded due to flooding from the Sulzbach stream that flows past. Efficient pumps could not be used, so that operations in Perneck had to be abandoned around the turn of the century.
In July 1954 there was a major flood in Perneck. Below the Maria Theresia tunnel, a large reservoir had formed due to the tunnel heap. The heap had grown excessively due to the expansion of the Maria Theresia tunnel. During the night of July 8, the entire stockpile slid into the flood-bearing Sulzbach and was swept away. The removed rock material completely filled the upper gypsum coating. With a depth of 17 m and an area of 700 m², the upper gypsum lacquer pit was the largest gypsum pit in Perneck.
In the 19th century, gypsum was also quarried in the area around Perneck at the former Steinberg mining area . Gypsum outcrops on the Törlbach near the former "Schaffer saw" and extensive gypsum pinings in the area of the Steinberg tunnels still indicate this extensive mining.
Gypsum mining in Obereck was continued by the Schiendorfer family, Obereck 11, in opencast mining and continued until about the First World War. The mining license for this mining was sold to the Linz entrepreneur Josef Flatz and subsequently a tunnel was dug.
In 1944, on the basis of a site plan drawn up by Markscheider Rettenbacher, a tunnel was dug to underpass the former opencast mine. The starting point was 25 m lower than the open pit. Russian prisoners of war began driving the tunnel, which was designed to be 3 m wide for double-track mining. Unfavorable rock conditions and a lack of mining knowledge repeatedly led to collapses, so that work came to a complete standstill after around 20 m of advance.
In the autumn of 1946 another attack was attempted. The single-track tunnel, now driven with a smaller profile, reached the gypsum block after 185 m. The device and the dismantling could be started.
During the first 10 years of operation, the output amounted to an average of 4,000 tons per year. The main customers were the Gmundner cement works Hatschek, which needed gypsum as an additive for cement production. Part of the funding was even sent to the CSSR. The average workforce was 4 workers and 1 employee.
In 1955, the "Linzer Handelsgesellschaft", whose sole owner was Lothar Flatz, was awarded the free-digging area including overshares. As a result, both the workforce and the production volume increased significantly. 6 to 8 workers and 2 employees were able to increase the raw gypsum production from initially 500 t/month to 1,000 t/month in the last few years of operation. From 1963, the funding went entirely to the Gmunden cement works Hatschek. The output of the pit was quite different depending on the needs of the Hatschek company, which was subject to economic and seasonal fluctuations. Despite this, the gypsum pit could not cover the raw gypsum requirements of the Hatschek cement works. In 1965, 3 additional Yugoslav guest workers were employed to increase performance.
The small amount of deposit substance that remained and the increasing deafness to the depths, which made the construction of another civil engineering project appear to be less than successful, prompted the mine operator to hand over the operating facilities to the Austrian Armed Forces. June 30, 1966 was set as the handover date.
As a result, the army built an ammunition store in the foothills of the gypsum deposit. The former civil engineering works were largely filled with jacking heaps. The relocation of the workings above the level of the conveyor tunnel was omitted because of the high costs. The old mine building was only used in exceptional cases, such as for the construction of emergency exits in the area of the old mining tunnel and the ventilation shaft.
The amount of raw gypsum extracted during the 20-year life of the Oberecker pit between 1946 and 1966 was around 100 - 120,000 t.
From a geological point of view, the Oberecker gypsum ridge, which lies in the course of a Juvavian overthrust zone, is genetically related to the Pernecker salt deposit due to isolated pieces of salt occurring in the gypsum. Due to the mutual distance between the two deposits of around 2 km, however, there is no direct spatial connection.
The approximately 40 m thick gypsum body is embedded in red and gray clay slate, which belongs to the Werfen layers of the Neokom. Its strike is approximately east-west. The deposit body dips at 45° to the south. Up to 60 m thick layers of gravel and marl form the hanging wall of the deposit, while salty lattes form the bedrock. The banded raw gypsum rock has a whitish, gray appearance. Anhydrite nodules of irregular size and distribution are embedded in the gypsum body. In addition, one often finds clay - gypsum - inclusions. The transition between the body of the deposit and the outskirts is not sharply demarcated, but is characterized by a gradual increase in barren components.
A borehole sunk above the production tunnel encountered red and gray clays at borehole meter 12 after penetrating through blocky moraine debris. Gypsum was applied from drill meter 35 to 43. The bore was stopped at a depth of 62.5 m in the marl. Another well drilled approx. 100 m SE of the gypsum pit encountered chert-bearing siliceous sandstone after a thin layer of moraine debris.
The pit's feasibility limit was 70% gypsum content. The average gypsum content of the hewn was 76 to 78%. The only secondary material found was clay, for which there were no sales opportunities due to the low but disturbing salt content.
The 185 m long exploration tunnel, which was started on the old Pernecker road at 580 m above sea level and whose axis pointed to the SW, penetrated tectonically disturbed layers of red, gray and black shale and marl. Due to the falling rock, the 1.90 m high and 1.30 m wide tunnel profile had to be completely lined with wood to reach the body of the reservoir. The single-track conveyor track, which had a gauge of 600 mm, had a gradient of 2.4%.
At the level of the extraction tunnel, the excavation was initiated as a trend-oriented local construction. Four mining roads were laid in the E – W direction, each 60 m long, 5 – 6 m wide and 2.7 m high. Safety pillars with a width of 3 to 4 m remained between the individual mining roads. 3 mining horizons, each with a floor spacing of 8 m, were created above the production tunnel. The individual excavation horizons were connected by a 48 m long and 40° incline. A 25 m long weather tunnel, the distance of which was 25 m from the hoisting level, formed the 2nd day opening. In the area of the workings and drifts that were driven within the deposit body, no lining had to be brought in.
The raw gypsum was obtained by shooting it in and filling it up manually in wooden boxes. The Hunte, equipped with cast-iron wheels, held approx. 1 m³ of heaps. In 1960, the specific consumption of explosives (Donarit I) was 310 g/t of debris recovered. The blast holes were drilled using electric hand drills.
The whole mine building was naturally ventilated. The weavers moved in at the extraction tunnel, reached the excavation levels via weather tunnels and weather pits and pulled out again via the weather tunnel. Even in summer, the weather current frequently reversed its direction. Because of the unfavorable weather conditions, the shooting time was shifted to the end of the shift.
The heaps won in this way were thrown down onto the hoisting floor via fall rollers, filled by hand in crate hoists with a content of 600 to 800 kg and brought to the surface by gravity.
The crushing plant was located at the end of the track after crossing the old Pernecker Street. The heap was tipped from the conveyor hoist into a 10 t intermediate bunker and transferred from there to the crusher, which was installed as a simple jaw crusher for crushing the coarsest pieces of the heap. The mouth width of the discharge side was 32 x 25 cm. The output of the crusher operated with a 17 hp drive motor was 5 t/h. Below the crusher was a 40 t silo. The raw gypsum was transported to the Ischl freight station by 5-ton truck and loaded onto freight wagons by hand.
Near the mouth of the tunnel there was a forge, material shed and arrival room. A barracks for 6 men was built at a distance. The buildings, entirely made of wood, were demolished at the beginning of the 1970s.
In 1952 the 1st working level was cut. The 2nd excavation level was prepared. The upwardly tapering body of the deposit led to a reduction in the length of the mining road to a few 10 m on the uppermost mining level. When mining the third mining horizon, a borehole was drilled into old burrows that were connected to open-cast mining, and water was thus brought in. Despite the damming of the borehole, the ingress of water could not be completely prevented. A dewatering system had to be installed, which was not necessary in the otherwise completely dry pit.
Since 1955, mining has taken place in two mining roads of the 1st underground mine, which was built 8 m below the mine level. The gypsum was mined in civil engineering in sloping chamber structures with a chamber width of 6 m and a chamber height of 4 – 5 m. The protective pillar width was an average of 4 m. The collected debris was removed by pulling up the filled box hoist over a 22° inclined bin level using an electric reel (traction force 1,000 kg, motor power 4 kW) onto the horizon of the extraction tunnel. At the end of 1961, the first civil engineering works were completely dismantled. The entire production was subsequently obtained from the remaining pillars of the production tunnel horizon. As a result of the excellent sales situation of the Hatschek company in the summer of 1962, 1,000 tons of raw gypsum could have been delivered per month. However, due to a lack of workers, the mine could not provide this funding.
In the winter of 1962, work was started on the second civil engineering project. With a workforce of 6 workers and 2 employees, the monthly production amounted to around 580 t. The die reached the 2nd level of civil engineering in the spring of 1963. After the start-up of the reel conveyor, work began on the construction of the 2nd level of civil engineering from east to west. 9 workers and 2 employees were able to increase production to 800 t/month. In June 1963 production dropped again to below 600 t/month due to a shortage of workers (4 workers were laid off).
The extractable substance had shrunk to 10,000 t in August 1965, with the same construction site size as in the first civil engineering. This corresponded to about one year's funding. In addition, investigations revealed that the deposit was becoming increasingly cloudy as the depth increased. For these reasons, the Oberecker gypsum mine was handed over to the Austrian Armed Forces on June 30, 1966 after mining activities had ceased.
Table 1: Promotion of gypsum mining in Obereck (source Montanhandbücher 1953 – 1967)
In the years that followed, the Federal Ministry of Defense (BLMV) built the "Perneck tunnel system" as a satellite storage facility for the Stadl-Paura army ammunition facility.
In the autumn of 1966, on behalf of the Federal Ministry of Defense, a tunnel under the former Oberecker gypsum mine was struck at Sulzbach - Strub. The road excavations were carried out by a consortium led by the Soravia construction company, which had previously built the road tunnel in Hallstatt. Up to 70 workers, mostly Carinthians, were on duty on the construction site every 10 days. A large concrete mixing plant, a compressor station and a transformer station were built near the Strub. The construction work lasted until 1969.
After completion of the installations and facilities, the Stadl-Paura army ammunition facility took over the "Perneck tunnel system". Ammunition was stored in the mostly newly excavated underground chambers. As part of the restructuring of the Austrian Armed Forces, the BMLV sought to sell the tunnel system from 2002.
The surface water penetrating the mountains constantly dissolves gypsum, which as a salt of sulfuric acid has good water solubility. Over time, the strongholds of the former gypsum mining chambers were weakened by the dissolving processes and large-scale subsidence and ping formations on the surface followed. Since the BMLV, as the successor to the mining authority, is responsible for protecting the surface of the ground, extensive renovations have to be carried out in the former pit of the gypsum mine. The 3 excavation horizons above the former main extraction tunnel were partly filled with sulphate-resistant lightweight concrete made from expanded clay granules ("Liapor") in order to prevent further subsidence at the surface. Furthermore, half-shells made of concrete were laid in the subsidence area for the rapid drainage of surface water. The former gypsum mine from the 19th century was also sealed. This restoration work continues to this day.
Reports from the Salzburg Mining Authority regarding gypsum mining in Oberecker from 1952 - 1967
Carl Schraml "The Upper Austrian Salt Works from 1750 to the time after the French Wars", Vienna 1934
Carl Schraml "The Upper Austrian Salt Works from 1818 to the end of the Salt Office in 1850", Vienna 1936
Joseph August Schulte's "Travels through Upper Austria", Volumes I + II, Tübingen 1809, reprint Linz 2008
Leopold Schiendorfer "Perneck - A Village Through the Ages", Linz 2006
Hans Kranabitl "Oberecker gypsum mining", reporting work Montanuniversität Leoben, Leoben 1983