Seltzer trachyte
| Seltzer trachyte | |
|---|---|
| Main features | |
| group | Volcanite |
| Subgroup | Trachyte |
| Occurrence | Germany, Rhineland-Palatinate, Selters |
| colour | light blue to light gray |
| use | Stone, facade cladding, floor coverings, worktops
|
| Dismantling situation | active breakdown |
| Division into hard and soft stone | > 5, hard rock |
| Age | Oligocene |
| Reference example | Selters market fountain |
| Special marks | numerous inclusions from rock fragments and minerals |
The seltzer trachyte is an Oligocene natural stone that is quarried in the Westerwald near Montabaur . This trachyte is named after the town of Selters . Due to its favorable material properties, it has been used for the production of stone and sculptures since the 18th century .
Formation and dismantling
The trachytes of Selters emerged in the Upper Oligocene as a result of intense volcanism in the Rhenish Slate Mountains , which was associated with the collapse of the Upper Rhine Rift and the Lower Rhine Bay . The trachytes, as effluent rock of the syenite , solidified as spring or dunnage near the surface. Due to the erosion of the softer side rock , these weather-resistant volcanic peaks form characteristic elevations today. The best known volcanic formation of this type is the Drachenfels in the Siebengebirge .
Trachyte has been mined in stone quarries in the area around Selters since 1770.
Rock formation and mineral inventory
The dense and fine-grained soda-trachyte is a light blue to light-gray volcanic rock, in its basic mass distributed irregularly, up to 8 mm wide, white to light gray alkali feldspar - and plagioclase - phenocrysts are embedded. In addition, smaller black biotite and hornblende crystals up to 4 mm in size can be observed. In some areas, iron precipitates appear in the rock, indicated by a red-brown discoloration of the rock. Due to its porosity , the seltzer trachyte sometimes shows peeled, superficial weathering.
Technical characteristics of the seltzer trachyte:
| Characteristic value | average value |
|---|---|
| Bulk density | 2.38 g / cm³ |
| porosity | 8.04% |
| Water absorption | 2.65% |
| Compressive strength | 114 kg / cm² |
| Frost protection | Well |
The seltzer trachyte consists on average of 80% basic mass, consisting mainly of alkali feldspars, plagioclases and opaque ores, 13% feldspar sparrows, 5% biotites and 2% accessories (mainly apatite , zircon , rutile , ore, hornblende).
use
The seltzer trachyte is a valued stone . Due to its resistance to weathering, it is particularly suitable for the production of facade panels and ashlar blocks as well as for sculpting for the production of sculptures.
Usage examples
- Market fountain in Selters
- Pedestal of St. Joseph's Church in Speyer
- Stone carvings on the Gothic portal of the Cologne town hall tower
- Hollerich lock
- Reconstruction material for the goose rider fountain in Essen
- numerous buildings in Selters
Individual evidence
- ↑ WD Grimm: A fine-grained trachyte: seltzer trachyte A fine-grained trachyte: seltzer trachyte. Building information, accessed on July 28, 2014 .
- ^ A b Johannes H. Schroeder: Stones in German Cities - 18 Discovery Routes in Architecture and City History . Berlin 2009, ISBN 978-3-928651-13-4 .
literature
- Karlfried Fuchs: Natural stones from all over the world. Callwey stone index in 2 volumes , Volume 2, Callwey-Verlag, Munich 1997, ISBN 3-7667-1267-5 , pp. 250f.