The natural stones used on the Romanesque north wall of the St. Martino church in Mendrisio

The natural stones used on the Romanesque north wall of the St. Martino church in Mendrisio Cavallo Giovanni*, Corredig Guido**, Dell’Oro Davide**, Galimberti Lucia**, Rodeghiero Franco**, Vezzoni Bruno* *University of Applied Sciences of Southern Switzerland, Dept. Environment, Construction and Design, LTS, PO Box 12 CH-6952 Canobbio (Tessin) giovanni.cavallo@supsi.ch ** University of Milan Bicocca, Dept. of Geology, Piazza delle Scienze 4 Milan (Italy) The Romanesque north wall of the St. Martino church in Mendrisio (fig. 1) has been chosen as model for an applied research project called OSMATER (http://istgis.ist.supsi.ch:8001/osmater/) aimed to link the original materials used, the quarries and the possible routes. Irregular scabbled stones of silicified limestones have been largely used for the wall corresponding to the oldest one. This stone is locally called Pietra di Salorino (Salorino stone) being the village part of the mining district. The upper part of the wall is decorated with small arches in Travertine called Tufo Lombardo (Lombard Tuff). The final cornice is in individual decorated blocks of sandstone. The correlation between the microstructure and the composition of the raw materials and the stones used on the wall allows to refer the silicified limestone to the quarry located at Monte Casima close to the Salorino village and the church. The rock belongs to the Moltrasio stone formation (Low and Middle Lias). It is a marly limestone, pale grey in colour, with veins filled up with coarse grains of calcite and nodules of flint. The Quaternary Travertine is locally called Tuff for its analogies with the volcanic rocks. The petrographic examination allows to refer this material to the Travertine deposits located in Rancate, a village close to Mendrisio. The sandstone belongs to the formation Conglomerate of Como (Oligocene); it comes from the quarries located in Malnate and is locally known as Pietra Molera. The colour ranges from grey to greenish, the grain size from medium to fine, the mineral phases are quartz, feldspars, biotite and muscovite. Grains of metamorphic and carbonatic rocks are also present. The matrix is siliceous. The source of the silicified limestones and the travertine is just close to the building. The sandstone quarry is a little bit far from the church. Symposium 8: Building Stones – application, suitability, research