The origin of this rock, an accumulation of debris such as sand and gravel, lies in the dismantling of a mountainous belt that existed long before the formation of the Alps.

You may have already encountered the conglomerates of the northern border of the Alps known as “Nagelfluh”, a cemented gravel mixture of sand and rounded stones of different sizes. These conglomerates are the result of dismantling of the Alps by erosion and the subsequent deposit of debris.

Of similar origin, Verrucano is 200 million years older and resulted from the erosion of the central European Hercynian/Variscan massifs.

Verrucano consists of cemented gravel and sand and belongs to the so-called clastic sedimentary rocks. The red colouring is due to minute traces of iron. The light-coloured parts in the rock consist mainly of quartz from former pebbles or grains of sand.

If you take the path along the river from the Hotel Parc Naziunal Il Fuorn, the ground often has a purple colour – this comes from verrucano. The best place to see verrucano is at the entrance of the Trupchun valley; there are blocks of verrucano lying in the riverbed half way between the Prasüras car park and the Varusch hut.