On the south side, the massif of the Tödi is mainly composed of gneiss, which, according to Escher von der Linth, overlies a pioritic granite with large felspar crystals. The summit and the northern flank are mainly composed of metamorphic slate, in which talc predominates, but is sometimes replaced by felspar, so that the rock sometimes approaches the condition of gneiss and sometimes that of mica slate. There are manifest traces of anthracite, especially at the Bifertengrätli, where the rock in some places assumes the appearance of a quartzite mixed with fragment of talc, which has elsewhere in this region been referred to the Verrucano. To these strata succeed dolomite and Jurassic limestone, similar in character to those developed on a large scale in the canton of Glarus.