Table 3 Summary of the lithological classes, their description, and main

Vein quartz

White quartz grains, medium- to coarse-grained, partly dark enclaves (Fig. 3a)

Widespread

Quartzite

White-yellowish to dark, granular texture, fine- to medium-grained, a schistosity is sometimes visible (Fig. 3b)

St. Bernard nappe

Granite and metamorphic rock

Granite: Colourful and medium-grained (Fig. 3c), light and fine-grained, or reddish and fine- to medium-grained (Fig. 3d)

Gneiss and crystalline schist: Foliation at a mm- to cm-scale, alternating layers composed of light and dark bands (Fig. 3e, f)

Amphibolite: Metamorphic rock with dark amphiboles and light feldspar, medium-grained (Fig. 3g)

External massifs

Serpentinite and green crystalline

Green serpentine, magnetic, and other greenish lithologies (Fig. 3h)

Zermatt-Saas Fee unit

Sandstone

Colourful (Fig. 3i), dark (Fig. 3j), or beige, fine- to medium-grained, reacts with HCL 3.2%

Widespread

Dark-coloured limestone

Dark-coloured limestone: Dark, micritic-sparitic, fine veins, reacts strongly with HCL 3.2% (Fig. 3k)

Siliceous limestone: Dark, micritic, reacts weakly with HCL 3.2%, scratches the hammer

Helvetic nappes, Penninic sedimentary nappes

Light-coloured limestone

Light- and flesh-coloured limestone: Beige-reddish, micritic, veins, reacts strongly with HCL 3.2% (Fig. 3l)

Oosparite: 1–3 mm-large ooids, grain supported, reacts with HCL 3.2% (Fig. 3m)

Penninic sedimentary nappes, Jura Mountains

Niesen- and Gurnigel-Flysch

Colourful breccia, angular components of different size, orange weathered dolomite grains (Fig. 3n, o)

Penninic Flysch

Others

Volcanic rock: Phenocrysts in a fine-grained matrix, matrix supported, different colours

Conglomerate: Various rounded clasts in a fine-grained matrix

Claystone: Reddish—dark, soft

Unknown: Pebble cannot be assigned to a lithology

Molasse conglomerates, Molasse units, widespread