Soapstones: fields and production laboratories between Ticino and Moesano

Schenker, Filippo and Scapozza, Cristian (2019) Soapstones: fields and production laboratories between Ticino and Moesano. In: Geomorfologia & Società Biennial conference 2019 of the Swiss Geomorphological Society (SGmS), Bellinzona.

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Abstract

The soapstone fields known along the Alpine mountain range in the territory of France, Italy and Switzerland are about ~400 of which 120 are located in Southern Switzerland (Ticino and Moesano) together with 14 production laboratories. The extraction, the use and the function of soapstone manufactories have influenced the historical and economical evolution of Alpine etnographic contexts since the Iron Age, with a peak of production of pots (“laveggi”) between the last centuries of the Roman Empire and the Late Middle Ages. The recovery of this historical identity is based on the study of archeological artifacts and on the reconstruction of historical commercial networks. For this purpose, tracing back the extraction site of an archeological artifact becomes fundamental to reconstruct the ancient commercial roads across the Alps. The mineralogical content of soapstone artifacts has successfully been used to distinguish the provenance of artifacts coming from the Valtellina or from the Val d’Aosta. However, the petrographic method shows some limits because several types of soapstone can be found in more than one Alpine region. Here, we present (i) a database of soapstone fields and production laboratories updated after Pfeifer and Serneels (1986) and Mannoni et al. (1987) that includes new findings and (ii) new bulk-rock geochemical analyses to support the petrographic characterization of soapstones. The small differences in mineral and in major- and trace-elements compositions should help to localize the fields. Eight types of soapstone can be distinguished in southern Switzerland; some of them are characteristic of a specific area. The preliminary geochemical results show that the chemical composition can be significantly different even between the same type of soapstone and that H2O and CO2 (LOI), U and Cr can be tentatively linked to the metamorphic grade and the mineralogy of the soapstone, permitting to better reconstruct the geological framework of the rock and therefore also the location from which it has been extracted.

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