The millstone trade from the most exploited Italian volcanic areas: an overview from the phoenicians to the roman period

Lavas were widely used in antiquity to produce millstones. This is mainly due to their superior properties for grinding cereals and availability when compared with other rock-types. In the past four decades, several studies have been published about lava millstones discovered in subaerial and submarine archaeological sites of the Central-Western Mediterranean. Although the morphological evidence of old quarries is rarely present, all these studies were aimed at recognizing provenance and manufacturing areas of the volcanic raw material. Typologies of grinding tools coexisted in different periods, even if some technological developments marked transitions between cultures. The main chronology is: Archaic saddle quern, Greek hopper-rubber (Olynthian), small to medium size rotary device (Morgantina type) and large hourglass rotary millstone (Pompeian style). Potential volcanic sources are widespread throughout the entire Mediterranean region, but two main Italian quarrying areas of volcanic rocks for the manufacture of millstones from the Phoenician to the Roman period were pointed out. These are the Latium-Umbria border in Central Italy, and Sicily (Eastern Sicily and Sicilian Channel) in Southern Italy. In detail, analysis of the lava lithotypes shows that grinding tools were mainly constructed of: (i) a leucite phonolite of the so called “Orvieto quarries” between the localities of Sugano and Buonviaggio in the Roman Volcanic Province (High-K alkaline series); (ii) hawaiites and mugearites (Na-alkaline series) from Etna volcano; (iii) basalts (Tholeiitic/Transitional series) of the Hyblaean Mountains and (iv) basalts (Na-alkaline series) from Pantelleria Island (Sicilian Channel). Although some lava millstones from other volcanic regions are recorded, the above four Italian volcanic rock types represent the most exploited in antiquity. A comparison between volcanic millstones and outcropping lavas already exists, from literature data, through thin section modal mineralogy and conventional igneous petrology (i.e., TAS classification, magmatic affinities, and major-trace elements signature). Therefore, on this basis we propose a set of discriminating geochemical parameters (major-trace elements and element ratios diagrams) useful for a quick assessment tool to possibly evaluate one of these four exploited volcanic areas of Italy matching millstones. A sketch of volcanic millstone trade networks and commercial routes in antiquity throughout the Central-Western Mediterranean has been also reported and overviewed on the basis of the literature data.