The exploitation of natural resources was one of the factors in the economic development of Western societies from the end of the Middle Ages. Throughout Europe and beyond, mineral and wider rural wealth has been increasingly used and serves the nascent industrial development. Businessmen and Siennois technicians were involved in developing the resources of the Tuscan region (rich in particular of known minerals and used from at least ancient times) and more widely on the Italian peninsula. This first meeting aims to shed light on the industrial, commercial and financial practices of Siennois, and in particular by bankers such as Ambrogio Spannocchi or Agostino Chigi, who closely controlled, between the end of the 15th century and the beginning of the 16th century, most of the alunite deposits — the ore needed to make the alun — in Italy: those near Rome in Tolfa, near Naples, Pouzzoles and various parts of Tuscany, with the support of the Apostolic Chamber, have a form of operating monopoly.