Within six years of the invasion of 43AD., the Mendip lead mines were in full production. By 70AD., Britain was the biggest supplier of lead and silver to the empire. It reached such a level that the Spanish lodged a complaint with the emperor as their lead trade had fallen to such a low level. The emperor responded by setting limits for Britain's production, but it didn't affect production. Lead was in such high demand that the number of mines actually increased despite the limitations and output rose. New mines opened and a large part of Wales and North-West England was being mined for lead by the end of the century.
The aqueduct at Chesters (Hadrian's Wall)
Originally lead mines were under direct control of the Roman authorities, such was their desire to ensure as few people as possible were involved in lead mining. They believed the more companies that were involved in mining, the greater the opportunity for theft and fraud. Lead was so much a base necessity in the empire, they also wanted to ensure that they was little chance of any unrest that could spoil production targets.
Eventually the Romans capitulated and in about 60D, around the time of the Boudiccan rebellion, they agreed to hand over responsibility to two trusted agents, Gaius Nipius Ascanius and Tiberius Claudius Triferna. This is known as their insignia appears on lead ingots that appeared after this time.
Under the control of these two businessmen, the lead mines were leased out to private companies on payment of a levy. In return had to pass over half the lead mined to the government's imperial procurator to be given to the government. The remaining half they could sell on the market. Most of the lead was sold to the biggest user of lead, the government.
The Roman empire was rife with corruption, and mining was no exception. Four lead ingots bearing the mark of Triferna have been found hidden underground at Green Ore in the Mendips. When analysed, it was found the silver had been extracted from three bars and the fourth still had the silver deposits intact. Despite stringent controls imposed by the Romans, it seems he did manage to make a tidy income from his illicit actions. He was either brave or foolish, as his actions were punishable by execution or a life of toil in the mines. Execution in Roman times was carried out in the public amphitheatre. The main method was for the victim to be eaten alive by wild animals.
Mining was not a job anyone volunteered for. So the mines were manned by slaves, criminals and prisoners of war. Those who resisted a life of mining were thrown into a much more dangerous and short lived occupation. They became gladiators.
Lead mining was not as hazardous as gold mining as lead was taken from open cast mines on the surface. Even so it was still harsh work and about 12% of all miners died each year because of their daily labours.
Extracting the silver
The Romans taught the British lead workers techniques for extracting the silver from the lead ore.
Firstly the lead was smelted in a furnace to remove the lead from the ore. Then the lead was removed and heated in a shallow hearth. Powerful hand operated bellows were used to raise the temperature to about 1,100°c and, at the same time, cause the silver to separate from the lead. It was at this point the silver was dawn off and poured into ingot moulds. This process was known as cupellation.
The remaining led was smelted again to remove any impurities, after which it was poured into ingots and left to cool.