Bollinger sandstone

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Quarry near Bollingen
Statue of Saint Barbara
Quarry on the Obersee opposite Bollingen

The Bollinger sandstone is quarried near Bollingen on the upper Lake Zurich in Switzerland. Since it is a relatively large occurrence, the Bolliger sandstone is also called Uznaberger sandstone or Lehholz sandstone , depending on the mining locations . It is a molasse sandstone and was created in the Oligocene .

Rock description and mineral inventory

The Bollinger sandstone is lime-bound. Its color ranges from blue-gray to gray-green. It contains 30 to 50 percent quartz grains and 25 to 35 percent feldspars as well as 4 to 8 percent mica and chlorite , and the proportion of lime as a binding agent is between 5 and 18 percent. Partly clay deposits up to a centimeter in size can be found in the Bollinger sandstone, which the stonemasons call Gall . These are no damage, because they are rinsed out when exposed to weather. The grain sizes vary due to the size of this deposit. There are lighter and darker layers.

Occurrence

The rock deposits of this molasse sandstone are found in the hills on the northern bank of the Upper Lake Zurich .

Bollinger sandstone is extracted from various mining sites in the communities of Eschenbach, Schmerikon and Jona. Since some of the mining areas are located in nature reserves, the so-called shaft dismantling process with wire saws and scrapers is used to mine vertically to a depth of 60 meters. This should protect the nature reserves. After the blocks have been sawed free, cranes that can lift up to 100 tons are used to move the blocks upwards from the respective fracture layers. The thickness of the deposit allows the extraction of blocks of up to 25 tons.

use

Einsiedeln Monastery

Thanks to its structure (no bearing layers), the monolithic Bollinger sandstone is well weather-resistant. This sandstone is mainly used for solid buildings, bricks, bridge structures, window and door frames as well as stairs, facades, fountains, baths, garden designs, tombs and sculptures. The Bollinger sandstone was probably already mined around 1000.

There are numerous abandoned quarries around Bollingen. This sandstone is of great architectural significance for Switzerland and beyond, because it could be shipped to Germany. Well-known buildings made of Bollinger sandstone are the collegiate church of St. Gallen , the Fraumünster and Grossmünster , CS headquarters on Paradeplatz and the Einsiedeln monastery .

See also

literature

  • Friedrich Müller: International Natural Stone Index (INSK ), 10th volume, 3rd edition 1993, Ebner Verlag, Ulm 1993.

Individual evidence

  1. ↑ Müller: Natural stone index, 6.4.7 (see literature)
  2. ↑ The Bollinger sandstone quarries