The development in the Classical period of washeries where the crude ores were processed for smelting marked a big step forward in Athenian silver production, since they made it possible to exploit the hitherto unusable poorest argentiferous deposits. The discovery and excavation of the washeries and ergasteria have illuminated the technological advance from the pre-Classical two-phase to the Classical three-phase system. The earliest washeries were located perforce close to natural water sources, but when these became inadequate for the growing needs of the industry, ergasteria were built which, in addition to a washery, had a cistern to collect recyclable rainwater, and could thus be located close to the ore sources. Small communities in which the personnel lived and died grew up around them.