The Cluny Priory of Castelletto Cervo (Biella, Italy): Archaeometric Study of Mortars

The Cluny Priory of Castelletto Cervo (Biella, Piedmont) was deeply investigated from 2006 to 2014, in a multidisciplinary project. This contribution deals with the methodological approach followed for the archaeometric study of mortars, and the results in term of material knowledge and reading of the building phases in a time interval of about a millennium. Petrographic observations combined with microchemical data showed that the local raw materials were exploited during a very long time span: the aggregates are polygenic sands, with a high percentage of volcanic rock grains, coming from the hydric basins of the Cervo River, and its tributary Ostola; the binders are mainly Mg-bearing lime, with a strong hydraulic component due to the reaction between the binder and the volcanic grains of the aggregate. A good match between mortars composition and building phases was determined only for some of the earliest phases of the monastery.