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Roman Mining Technology in Britain

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If you have a question about this talk, please contact Dr Geoff Hale.

Light refreshments from 7:00 pm

The Romans introduced advanced mining methods to Britain following their invasion in 43 AD, especially hydraulic mining using large volumes of water. They used the water in several ways: for prospection by removing overburden to expose bedrock, for development of veins , washing ore-containing material and powering machines for crushing hard rock ores. The methods are shown best at the gold mine of Dolaucothi following their invasion of South Wales in ca 74 AD and nearby sites in the Tywi valley. It followed the large scale mining developments in Spain (25 BC onwards).

The hydraulic remains at Dolaucothi are substantial and show how the mine developed from prospection of surface deposits, discovery of veins, opencast working and finally underground exploitation. A small stream of water was used to wash both overburden and crushed rock using gravity separation to extract the gold. The largest reservoir was used in this way, and a later tank (Melin-y-milwyr) built close to the main opencast. Each system used a stepped series of tanks with washing tables between so as to maximise gold collection using riffle technology. Mercury amalgamation may have also been used to remove the last traces of gold dust. Surface gold came from the oxidised zone, where pyrites are converted to iron oxides, often liberating fine gold within the crystals.

Towards the end of the century, they penetrated vein deposits, and is attested by the discovery in the 1930s of a drainage wheel fragment in a deep stope. It was part of a sequence of such wheels, well known from southern Spain at Rio Tinto and elsewhere (Portugal and Dacia). Gold separation became more difficult and needed crushing machinery, especially a four-stamp mill worked by an overshot waterwheel. The fragments would then be ground to fine flour before final washing. Some gold may have been lost since it was locked inside pyrites. Both surface and underground mining needed skilled, honest and reliable labour, probably soldiers rather than slaves.

Other potential Roman mines occur in Mid and North Wales, Shropshire, the north Pennines and Scotland. They deserve intensive field work to examine reports of hydraulic remains.

Parallels with modern evidence of hydraulic mining include the known history of the California gold rush of 1848/9 and the Yukon rush of 1896/7, as well as evidence from Uganda from the 1930s, and Mongolia in recent times as the result of the financial crisis of 2008 onwards.

This talk is part of the Cambridge and Anglian Materials Society meetings series.

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