Lebacher egg
Lebacher eggs are Toneisenstein geodes (Sphärosiderite) which, in the Saar Rotliegend Palatine , especially of the eponymous region in Lebach in the Saarland from the 16th to the 19th century when iron ore was reduced. The oval shape of the geodes, whose iron content can exceed 20%, also gave it its name.
Emergence
The Lebacher eggs are diagenetic formations. They originated in the early Permian around 290 million years ago in fine-grained, dark sediments , which have been handed down in the form of thin-plate, dark, bituminous claystones and are assigned to the Odernheim Formation of the Glan group of the Rotliegend of the Saar-Nahe basin . At the time, these sediments were a sludge on the bottom of a freshwater lake ("Rümmelbach-Humberg-See"). Which processes are responsible for the formation of the geodes can only be guessed. The iron is believed to have come from the lake sediments themselves. Originally it was finely (dispersed) distributed in the sludge and could initially by reducing Fe 3+ (from e.g. hematite , Fe 2 O 3 ) to Fe 2+ as iron hydrogen carbonate (Fe (HCO 3 ) 2 ) into a water-soluble one Have been brought into shape. The reduction could have been favored by the metabolic activity of bacteria. As a result of the compaction of lower-lying, older sediment layers, water containing iron hydrogen carbonate was expelled from these and slowly but steadily rose to higher, younger sediment layers. The cause of the re- precipitation of iron in the form of iron carbonate ( siderite , FeCO 3 ) in the younger layers can be explained by the reduction in ambient pressure experienced by the rising solutions, because a decrease in pressure leads to the escape of carbon dioxide (CO 2 ) from the Solution and thus for carbonate precipitation (Fe (HCO 3 ) 2 → FeCO 3 + CO 2 + H 2 O). Certain sediment particles are likely to have acted as crystallization nuclei , so that the iron carbonate only precipitated at very specific points in the sediment. Where the felling had once started, it continued continuously, and so over time the relatively large clay iron stone odes that are known today as Lebacher eggs were created.
Iron ore
The Lebacher eggs were to the 19th century as ore mined in large open pits (Scots) and partly underground and iron production for. B. used in the Dillinger Hütte . The main mining area was between Rümmelbach and Gresaubach. Many of the basics of the historical use of Lebach eggs in the concession area of the Lebach ore mines were presented in book form. Other mining areas were near Nonnweiler, Oberlöstern, Schmelz, Steinbach and Sotzweiler. The Lebach eggs from the Lebach ore field were smelted in Bettinger Schmelze (Schmelz), Nunkircher Schmelz (Wadern), Neunkircher Eisenwerk (Neunkirchen), Alte Schmelz (St. Ingbert) and in the Saarbrück-Usingischen Hütte ( Fischbach ).
Fossils
Fossil collectors and palaeontologists value Lebach eggs because of their fossil content. A connection between the formation of a geode and the presence of a decaying carcass in the sediment is generally considered plausible, because the metabolic activity of the decomposing bacteria can create a chemical environment favorable for the precipitation of minerals such as siderite, but in the case of the Lebach eggs it is Connection not proven. Most Lebacher eggs do not contain any fossils. The fossils contained in the Lebach eggs are likely to be traced back to carcasses that were only accidentally encrusted with siderite. Inside the concretions, however, they were then better protected from further diagenetic and weathering flows and thus protected from destruction than the fossils in the unmineralized sedimentary rock. An exhibition in the Urweltmuseum Geoskop at Lichtenberg Castle near Kusel offers an overview of the fossils that have been handed down inside Lebach eggs. Another exhibition of such finds can be seen in the town hall of Lebach.
Geotourism
Since 2015, hikers interested in geology and paleontology have been able to explore the Rümmelbach Shark Trail . The 3.5 km long circular hiking trail leads through terrain whose subsoil is made up of the slate-like sedimentary rocks of the Odernheim Formation and contains Lebach eggs. The path got its name from the fact that freshwater sharks lived in the lakes of the Rotliegendzeit . Numerous display boards positioned on the hiking trail provide information about the rocks, fossils and historical iron ore mining in the area. The 9.5 km long Rümmelbach-Humberg-Weg , which is thematically more dedicated to mining and leads past several old iron ore mines, has existed since 2010 .
literature
- Gerhard Müller: Lebacher clay iron stones ("Lebacher eggs"). In: Edgar Schwer (ed.): The ore mining in the front high forest 1850-1870. Hochwälder booklets on local history. Volume 28, Issue 47, pp. 4–15, Nonnweiler 2011 ( geosaarmüller.de ).
- Ilse Winter-Emden: History of the Lebach ore mines and their importance for the region. Volkshochschule Lebach e. V., 1995 ( PDF 5.2 MB)
Web links
Individual evidence
- ^ I. Winter-Emden: History of the Lebach ore mines and their importance for the region. 1995 (see literature ), p. 43
- ^ A b G. Müller: Lebacher Toneisensteine ("Lebacher Eggs"). 2011 (see literature )
- ↑ Lebacher eggs. Heimatmuseum Neipel (www.neipel.de), accessed on December 10, 2016
- ^ I. Winter-Emden: History of the Lebach ore mines and their importance for the region. 1995 (see literature )
- ↑ Shark trail near Rümmelbach. Leaflet, City of Lebach, 2015 ( PDF 1.7 MB).
- ↑ Carolin Merkel: Shark trail attracts the curious: Numerous hikers came to the opening of the circular trail in Rümmelbach. Saarbrücker Zeitung (regional section Lebach), April 28, 2015
- ↑ Hiking on the bottom of the primeval lake. Saarbrücker Zeitung (Saarland regional section), July 23, 2010