Quartz

Quartz is a well-known rock-forming mineral occurring in granites, gneisses as well as sandstones and conglomerates. Occasionally, it can be the sole mineral forming a rock. One process that forms these monomineralic rocks is when they are precipitated from a solution containing solely silica oxide. 

At high temperatures and pressures certain minerals dissolve in the hot waters that circulate deep in the Earth's crust. The hot solution deposits mineral crystals in the cracks and joints of the host rock as the fluids cool and migrate upwards towards the surface. The resulting mineral filled cracks are termed hydrothermal veins. Quartz is among the most frequent minerals filling up such cracks.

The quartz veins are very resistant relative to the host rock and form prominent ridges across the landscape. Bohemian quartz wall is a spectacular example of a mineralized joint – a suture in Earth´s crust annealed by quartz. Segments of this quartz wall are arranged in a 100 km long belt extending from Furth im Wald in Bavaria via Domažlice and Přimda areas to Aš. The cliffs near the road from Hazlov to Aš represent the northernmost occurrence of the natural wall, called Goethe´s cliff in memory of poet and scientist J.W. Goethe.

Sample donated Lesy České republiky, s.e. – Regional directorate Western Bohemia.