Selagite, scattered all over the place and quarried on several fronts along this itinerary, is unique to these places and has been used since the Etruscan-Roman period. One example is the famous three Etruscan heads of the gate Porta dell’Arco in Volterra. This is a magmatic rock that solidified at small depths and then emerged. The geologist Paolo Savi, struck by the lively brilliance of the small but numerous biotite crystals, called it “selagite” (from the Greek selaghèo: shining, brilliant). As we walk through the village, we are always accompanied by its “brilliance”.