The Groppenstein gorge is the geographical border between the Sonnblick and Reißeck groups. The creek bed of the Mallnitz creek (near the inn “Zur Guten Quelle”) has a smooth polish that results from the Auernig-Törlkopf rockslide and consists of greenstone.
Other minerals to be found here are quartzites, phyllites and granite gneiss. The vegetation along the creek features large-leafed butterbur, Great Marsh Thistles, Marsh Cranesbill and other rare plants such as orchids and clematis.
Besides the spruce forest that dominates the vegetation, grey alder, ash trees, elms, fir trees and beeches can also be found. In early summer, Groppenstein gorge is an absolute paradise for birds – dippers, blue tits, great tits, finches, wrens, blackcaps, chiffchaffs, coal tits and many other species of birds congregate here, as do rare fire salamanders.