sentences:  Stratigraphically equivalent rocks on the mainland are clastic sediments with coal beds, marine to brackish fluvial units and travertines.The earliest mining on the island has been dated to around 13,000 BC, when paleolithic miners dug a shaft at the site of the modern-era Tzines iron mine for the extraction of limonitic ochre.Mining for base and precious metals started around the 7th century BC with the Phoenicians, followed in the 4th century by the Greeks, then the Romans.