Verifying the reliability of historical sources through a mineralogical and petrographical approach: the case of the "black-grren stone" from the Messina cathedral (Sicily, Italy).

The aim of this work is obtaining information on the provenance of some very peculiar green (or blackgreen) stones used both as façade and floor decorations in the Messina Cathedral. Historical sources and available literature data suggest that these materials could belong to the amphibolite of the Peloritani Mountains. In order to verify the true provenance, some stone samples were studied through various analytical methods (SEM-EDS, XRPD, XRF). The investigated specimens resulted to be metabasites showing pseudomorphic and vein textures, with relicts of olivine replaced by serpentine - forming a mesh textures - and orthopyroxene mostly altered to bastite. Pseudomorphic minerals are serpentine (lizardite and chrysotile), magnetite, amphibole (tremolite-actinolite series) and chlorite (talc-chlorite). These results demonstrate that the analysed green stones cannot belong to the amphibolite outcrop of the Peloritani Mountains. Otherwise, they show mineralogical and petrographic features very similar to those of “verde Calabria”, a rock typology largely exposed in the Northern Calabria area - belonging to the ophiolitic series - and widely used in the last century as building material.