Petrographic features, genesis and provenance of Pietra Paesina collections of Regional Museum of Natural Sciences of Turin, Italy.

Ruin marble outcropping in central italy always arose the contemplative interest of collectors and artists. With his geometrical, vividly edged and irregular colour patterns, this biomicrite, which is worldwide known as Pietra Paesina, remind painted landscapes or ruined villages. Even though the first aesthetical descriptions go back to XVII century, it was just in 1970 that Civitelli put a first light on the genesis of the rock, evidencing the non tectonic origin of its structure. Later on, the colour banding was correlated to the so called Liesegang phenomenon, with the periodical precipitation of iron oxyhydroxides following the infiltration of oxidizing ground waters during diagenesis and weathering. This works updates the previous hypotheses and demonstrate the possibility of mapping the concentration of diagnostic elements through different samples from Italian central-northern Apennines (Tuscany, Emilia Romagna, Southern Piedmont) by means of non-invasive techniques. Studying the Pietra Paesina ancient stone collections preserved in the Regional Museum of Natural Sciences of Turin, we compared the results of the traditional electron microbeam techniques with those of a bench-top micro-fluorescence instrument. With the limitations linked to the dimensions of the sample chamber, micro- XRF resulted to be a useful tool for the fully nondestructive analyses, allowing the distinction between different Italian varieties and setting the base for the provenance determination of ancient stone artifacts. Minor and trace elements quantification evidenced Mn, Sr and Ti concentrations as the most discriminatory parameters for provenance identification. Colour changes showed strict correlation to iron content, the percent variations depending on the composition of each sediment. Capillary forces controlling iron precipitation from weathering solutions are strongly influenced by the sedimentary structures, resulting in complex systems of dark bands and modifying the regula