The earliest sources of tin in the Early Bronze Age in the Near East are still unknown and the subject of much debate in archaeology.) Possibilities include minor now-depleted sources in the Near East, trade from Central Asia, Sub-Saharan Africa, Europe, or elsewhere.
It is possible that as early as 2500 BC, the Ore Mountains had begun exporting tin, using the well established Baltic amber trade route to supply Scandinavia as well as the Mediterranean with tin. By 2000 BC, the extraction of tin in Britain, France, Spain, and Portugal had begun and tin was traded to the Mediterranean sporadically from all these sources. Evidence of tin trade in the Mediterranean can be seen in a number of Bronze Age shipwrecks containing tin ingots such as the Uluburun off the coast of Turkey dated 1300 BC which carried over 300 copper bars weighing 10 tons, and approximately 40 tin bars weighing 1 ton.  Evidence of direct tin trade between Europe and the Eastern Mediterranean has been demonstrated through the analysis of tin ingots dated to the 13th-12th centuries BC from sites in Israel, Turkey and modern-day Greece; tin ingots from Israel, for example, have been found to share chemical composition with tin from Cornwall and Devon (Great Britain).
While Sardinia does not appear to have much in terms of significant sources of tin, it does have rich copper and other mineral wealth and served as a centre for metals trade during the Bronze Age and likely actively imported tin from the Iberian Peninsula for export to the rest of the Mediterranean.
By classical Greek times, the tin sources were well established. Greece and the Western Mediterranean appear to have traded their tin from European sources, while the Middle East acquired their tin from Central Asian sources through the Silk Road.  For example, Iron Age Greece had access to tin from Iberia by way of the Phoenicians who traded extensively there, from the Erzgebirge by way of the Baltic Amber Road overland route, or from Brittany and Cornwall through overland routes from their colony at Massalia (modern day Marseilles) established in the 6th century BC. In 450 BC, Herodotus described tin as coming from Northern European islands named the Cassiterides along the extreme borders of the world, suggesting very long-distance trade, likely from Britain, northwestern Iberia, or Brittany, supplying tin to Greece and other Mediterranean cultures.  The idea that the Phoenicians went to Cornwall for its tin and supplied it to the whole of the Mediterranean has no archaeological basis and is largely considered a myth.
The early Roman world was mainly supplied with tin from its Iberian provinces of Gallaecia and Lusitania and to a lesser extent Tuscany. Pliny mentions that in 80 BC, a senatorial decree halted all mining on the Italian Peninsula, stopping any tin mining activity in Tuscany and increasing Roman dependence on tin from Brittany, Iberia, and Cornwall. After the Roman conquest of Gaul, Brittany's tin deposits saw intensified exploitation after the first century BC.  With the exhaustion of the Iberian tin mines, Cornwall became a major supplier of tin for the Romans after the 3rd century AD.
Throughout the medieval period, demand for tin increased as pewter gained popularity. Brittany and Cornwall remained the major producers and exporters of tin throughout the Mediterranean through to modern times.