The subsoil of the island consists mainly of schist, gneiss and marble, but also is also mineral-bearing, containing argentiferous lead, copper, iron and zinc deposits, a fact that has played a catalytic role in the development of the island from prehistoric times, when exploitation of metalliferous deposits served to promote overall cultural development, being one of the main stages of transition from the Stone Age to the Bronze Age.
There are two arc-shaped mineral-bearing zones: One has argentiferous lead deposits and is located in the northern part of the island, stretching from the northeast to the southwest, between Agios Sostis, Agios Sylivestros, Vorini, Kapsalos and Xeroxylo.
The second extends from the area of Ai Yianni at Faros to Apokofto and Aspro Pyrgo.
Evidence indicates that the first mining activities for the extraction of silver and lead took place on the peninsula of Agios Sostis at least by the beginning of the 3rd millennium BC, which makes this mine the second oldest silver mine the world.
Archaic period (700-480 BC): Exploitation of the silver mines, on the site of Agios Sostis, Agios Sylvestros (or Sylivestrou), Vorini, Kapsalos, and Xeroxylou, and the gold mines near the location of Ai Yianni at Faros, Apokofto and Aspro Pyrgo.
19th and 20th century AD: Mining of iron ore at Agios Sostis, Agios Sylvestros (or Sylivestrou), Vorini, and Kapsalou.
Source: www.sifnos.gr