"The Divine Bounty has bestowed upon us inexhaustible mines of silver, and advantages which we enjoy above all our neighbouring cities, who never yet could discover one vein of silver ore in all their dominions." XENOPHON
The Silver MinesAthens was the only Greek polis (city-state) with the ability to dig its own wealth straight from the ground. Laurion was an area near the east coast of Attica rich in siver-bearing ores which had been exploited since the Bronze Age. In 482 BC a new vein was discovered which led to a massive increase in activity. Themistocles persuaded the Athenians to spend this new revenue on building a fleet of triremes which were used to defeat the Persians at Salamis in 480 BC.
The Scale of OperationsThere were about 350 mines producing 1000 talents a year, worked by 10-20,000 slaves. Mining rights were owned by polis, but leased to individuals by 10 annually elected poletai. The purity of the silver (which was protected by law) led to Attic "owls" being widely respected. They have been found as far afield as India and Algeria. The design with Athena on obverse and owl + olive-sprig on reverse was unchanged for centuries.
MiningOre extraction from very deep vertical mineshafts, off which were narrow and cramped horizontal galleries.
Preparation of oreOre separated from waste in special "washeries" (several have been excavated in the Laurion area, eg Agrileza, Thorikos).
CupellationImpure silver heated in a furnace or crucible with materials capable of absorbing the impurities (principally lead).
WorkforceAll were slaves. Numbers were large: Thucydides mentions 20,000 deserting to Decelea (encouraged by the Spartans to put economic pressure on Athens).
Factories were designed to minimise risks of slaves getting hold of silver. "Trusty" slaves were given incentives (own houses). Slaves would be owned by wealthy Athenians (like Nicias) and hired out to the lessees of the mines. They were usually prisoners-of-war, not criminals. Their life expectancy was short and they lived and worked in conditions of indescribable squalor.