Mineralogical clustering of the structural mortars from the Sarno Baths, Pompeii: A tool to interpret construction techniques and relative chronologies

•A novel approach for the quantitative phase characterization of ancient mortars is proposed.•The method combines the use of Rietveld refinement and principal component analysis.•The obtained results were cross-checked by petrographic and microtextural analyses.•The methodology was tested on the structural mortars of the Sarno Baths in Pompeii.•The results shed light on construction techniques and chronologies of the building.