Valser quartzite is found at the base of the powerful Aduladecke (lower Valserschuppen). The curved course of the minerals and quartz veins (back then, liquid prehistoric rock) and the multiple schistosity which can be seen in a slice of the stone, reveal which elementary powers were at work in the formation of the Alps.
The original age of the stone is very old, probably over 250 million years. About 50 million years ago, the Valser quartzite was transformed by the folding of the Alps, new minerals were created which were embedded in the rock, and the uniqueness of the stone was characterised by the colourful mixing of quartz and feldspar crystals.
Use of the stone
Valser quartzite has been quarried in Vals for hundreds of years. At first, the stone slabs were used principally to cover the roofs of houses (now compulsory). Today the local stone is also cut and polished for use in interior design.
The Therme is built from layer upon layer of stone slabs. The slabs are not mere facings; the massive walls are supporting elements. The slabs were cut to size in the quarry, precisely according to Peter Zumthor's instructions, and set up on the building site according to his plans. The slabs are cut to the highest degree of accuracy with the most precise tools: the production tolerance was in the 1/10 mm range. In total, 60,000 slabs were used. The full range of finishing possibilities for Valser quartzite has been used in the Therme: split, milled, sawn, ground, stacked, polished, broken but always worked with absolute precision.
Certain elements (floor and ceiling in the thermal spring grotto) weigh over 4 tonnes each.
Fine grained, massive, slated, micaceous quartzite with rough banding of green, light bluish, micaceous layers, some eyed, alternating with light grey to white quartz layers.
1. Bulk density kg/m3 2698
2. Bending extension strength 27.5 N/ mom
3. Very high frost resistance (freeze proof) according to Dobrolubov-Romer
4. Water absorption mass % vertical (walling) 0.015, horizontal 0.4
5. Porosity vol. % 0.8
- Quartz 0.03 - -0.4 (60%)
- Lime feldspar, poecilitic pigmented with traces of ferrous oxide 0.3 - 0.6 mm
- Light mica 0.1 - -0.6 mm
- Biotite 0.05 - -0.3 mm
- epidote, clinozoisite