Drachenfels (Siebengebirge)
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The Drachenfels is a hill in the Siebengebirge uplands between Königswinter and Bad Honnef in Germany. The hill was formed by rising magma that could not break through to the surface, and then cooled and became solid underneath. It is the subject of much tourism and romanticism in the North Rhine-Westphalia area.
Drachenfels, view from Mehlem
Drachenfels – aerial view
The Drachenfels in 1624 by Matthäus Merian. The slide used to transport the rock from the quarry to the Rhine is shown, as is the (now disappeared) Burg Wolkenburg and an intact Burgfried. The engraving is an advertisement for glass windows.
Königswinter and the Drachenfels. Postcard in Photochrom, around 1900
Trachyte
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Trachyte is an extrusive igneous rock composed mostly of alkali feldspar. It is usually light-colored and aphanitic (fine-grained), with minor amounts of mafic minerals, and is formed by the rapid cooling of lava enriched with silica and alkali metals. It is the volcanic equivalent of syenite.
A cut sample of trachyte, with phenocrysts of sanidine, in a wall in Germany
Polished opal on trachyte
The Breadknife is a peralkaline trachyte dike in the Warrumbungles of eastern Australia.
Iron Pot is one of several trachyte plugs in the Hedlow Creek region west of Yeppoon in Central Queensland.