What did the ancient Greeks mine at Laurion, and when did they mine it?

The Laurion district was one of the most extensive and influential silver mining areas in the ancient world. Evidence from archaeology and lead isotopes indicate that it was exploited for silver from the 4th millennium BC, probably accompanied by production of lead and copper, with exploitation of iron considered very likely in the 1st millennium BC. This paper integrates new and existing information to reassess the character of the mineralization mined by the ancient Greeks. It then applies these results to assess when the differing styles of mineralization may have been mined. The outcomes have significant implications for archaeology at Laurion. Foremost is the contrasting character of mineralization at the first and third contacts. Their significant differences are considered in several contexts: stratigraphy and structure; distribution of the mineralization; what the ancients mined; the impacts of weathering and oxidation; and their differing silver content. As a result, we believe that production from the exposed and shallow first contact mineralization was largely based on widely dispersed, thin, irregular, oxidised and lower grade deposits. These would favour numerous small independent operations with variable production that began in the 4th millennium BC and continued until the 1st millennium BC. In contrast, production from the third contact was based on substantial, thick, continuous and higher grade deposits, focussed around the central area of Kamariza. These deposits would support several larger scale, continuous and systematic mining and processing operations capable of providing a surge in silver output that could be maintained at a much higher level. This contrast in the character and grade of mineralization at the first and third contacts is sufficiently strong to link discovery of third contact mineralization with the windfall surplus received by Athens, according to Herodotus (VII.144), and dated at 483/2 BC by Aristotle (Ath. Pol. 22.7).