Most of the base of the mountain lies in the Tsaté nappe, a remnant of the Piedmont-Liguria oceanic crust (ophiolites) and its sedimentary rocks. Up to 3,400 metres the mountain is composed of successive layers of ophiolites and sedimentary rocks. From 3,400 metres to the top, the rocks are gneisses from the Dent Blanche nappe (Austroalpine nappes). They are divided into the Arolla series (below 4,200 m) and the Valpelline zone (the summit). Other mountains in the region (Weisshorn, Zinalrothorn, Dent Blanche, Mont Collon) also belong to the Dent Blanche nappe.