Petrological footprints of the millstones of Megara Hyblaea (Sicily Island, Italy) highlight the human interactions with Mediterranean volcanoes

A petrographic and geochemical study of several volcanic millstones, representative of 119 artifacts found in the ancient Greek colony of Megara Hyblaea (Sicily Island) and recording the grinding device evolution from the Archaic to the Hellenistic period, unravelled the volcanoes involved as quarrying and production areas. This was possible also through the comparison with available petrographic and geochemical literature data of ancient volcanic millstones found in the whole Mediterranean. Saddle querns, hopper-rubber, rotary Morgantina- and Delian-type millstones of Megara Hyblaea consist of lithotypes belonging to five magmatic series: Tholeiitic, Na-Alkaline, Tholeiitic Transitional, Calcalkaline and High-K Alkaline. A provenance from the Eastern Sicily, i.e. mugearites from Etna and basalts and basaltic andesites from the Hyblaean Mountains were recognized for all the four investigated grinding devices. By contrast, a sea-trade is involved for several saddle querns made of calcalkaline basaltic andesites and andesites lavas (Aegean Islands) and two Morgantina-type millstones consisting of a calcalkaline rhyodacite ignimbrite from the quarrying site of Mulargia (Sardinia). A wide millstone trade, both local (Eastern Sicily) or maritime (Central-Eastern Mediterranean) was thus constrained through six centuries, from the foundation of the Greek colony up to the destruction of the settlement at the end of third century BCE. Finally, Vulture Volcano (southern Italian peninsula) is the most probable candidate for the only leucite- and haüyne-bearing phonolite of the High-K Alkaline Series.