Historical Use of Lime in Some Islands of the Tuscan Archipelago (Italy) Where Stone for Lime Is Almost Absent

Abstract

The Tuscan Archipelago lies between the Ligurian Sea to the north and the Tyrrhenian Sea to the south and between Corsica to the west and the Tuscan coast to the east. It is made up of seven major islands, Elba, Giglio, Capraia, Montecristo, Pianosa, Giannutri and Gorgona (in order of size), and several smaller ones. Geologically, these islands are very different from each other. Elba combines all the characteristics of the northern Apennines with a large granodioritic pluton and a sequence of tectonic units with sedimentary successions of the Ligurian and Tuscan type. Giglio is a granitic pluton with a small patch of sedimentary cover. Capraia is an entirely volcanic island. Montecristo is a granitic pluton. Pianosa consists exclusively of Mio-Pliocene carbonate rocks. Giannutri consists of Mesozoic Cavernous Limestone, and Gorgona consists of calcschists, serpentinites and metabasites. This article examines the mortars used in the historical architecture of Capraia, Gorgona and Giglio, islands where limestones are almost absent, trying to investigate the provenance of the carbonate stones used to produce the lime through mineralogy–petrographic analyses. Mineralogical and petrographic analyses proved useful in identifying the raw materials used for the production of lime, also contextualising them in the historical and administrative vicissitudes of the islands. In particular, a magnesian lime of Ligurian origin was used in Capraia during the period when the island was under the rule of the Republic of Genoa. On Gorgona in the Middle Ages, the few outcrops of carbonate rock on the island, consisting of saccaroid marble, were exploited for the local production of lime, while in later times lime was sourced from the mainland. In Giglio, the small outcrops of dolostone and marbles on the western side of the island were exploited. This work has broadened knowledge in the use of materials and highlighted man’s knowledge of the area and its resources to such an extent that even small outcrops suitable for lime production were exploited. Attention is also drawn to the fact that, although sophisticated techniques provide excellent information, in many cases only a careful petrographic investigation allows the most useful information to be obtained in a cheap and easy way.