Siebengebirge - Geowanderung: Hühnerberg

In the middle of the Oberhau, almost as a landmark for basalt mining, stands the greenish-painted crusher tower of RPBL (Rheinische Provinzial-Basalt- und Lavawerke GmbH & Co. oHG, Sinzig), visible from afar, on the edge of the Hühnerberg basalt quarry. When magma rises almost unchanged through thin vents and solidifies on the earth's surface, a very fine-grained rock is formed, a volcanite, here in Hühnerberg basalt. Basalt is mainly used for road construction, as ballast for railroad lines and as an aggregate, e.g. in concrete production. As fused basalt, the rock is used as a lining for plant components that are subject to heavy abrasion. As can be seen in the adjacent aerial photo, mining has hollowed out the Hühnerberg and is now eating 90 meters deep into the earth. While the mountain was once 362 meters high, the edge of the slope is now 289 meters, meaning that 163 meters of basalt have now been extracted. Operations will continue in this way for several more decades. The basalt rock is loosened by blasting in six conveyor floors with a height of 30 meters, cleaned and then crushed into different grain sizes. This goes as far as basalt sand, which is used as filter sand or for soil improvement.