Sulfur was one of Sicily's most important mineral resources, which is no longer exploited. The area covered by the large deposits is the central area of the island and lies between the provinces of Caltanissetta, Enna and Agrigento: The area is also known to geologists as the chalky-sulfur plateau. But the area of mining exploitation also extended as far as the Province of Palermo with the Lercara Friddi basin and the Province of Catania, of which a part of the Province of Enna was part until 1928; it is the one in which sulfur mining, processing and transport took place in the last quarter of the millennium. For a time it also represented the maximum production area worldwide.