Britain was a land rich in mineral deposits just waiting to be mined. Those were the thoughts of Emperor Claudius and were part of the prelude to the invasion of Britain.
Britain was indeed abundant in metal ore, one of the main consumables in the Roman empire. It was not just iron and lead the Romans wanted to mine, there was also gold, copper and tin. Lead was the main requirement as it could be used for water pipes, guttering and, once liquefied in a furnace, mixed with tin to make pewter. But the Romans had a more important use for lead. They could extract the silver from the ore to make much needed coins and tableware.
|The lead mines and extracting silver|
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.
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.
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.
|Mining the gold|
It's not a well known fact, but Britain does have deposits of gold in it's landscape. Panning for gold in alluvial gravel had been carried out in streams in Cornwall and Scotland for hundreds of years before the Romans arrived. The large scale mining of gold was instigated at the only gold mine in Britain in Dolaucothi, Wales. The works can still be seen near the village of Pumpsaint
When the Romans conquered Wales in 70AD., they immediately set to work building reservoirs on mountains in the Cothi valley. A seven mile long aqueduct was built to move the water into these man made lakes. Then all together the water was released down the mountainside which created an avalanche consisting of water, plant life and top soil. It was a massive project and must have taken many months to complete. The end result was worthwhile. Once the surface layer had been removed, there was just bare rock and exposed seams of gold.
They wasted no time in putting the slave labour to work digging the shafts that followed the seams deep into the mountains. Initially the gold was extracted by the open cast method where it was dug from the surface. As they when followed the seam deeper into the rock other methods had to be used.
The rock was tough so the Romans used a process of fire-setting to break up the rock and so make it easier to remove. Fire-setting was the process of building a bonfire of wood in the shaft and raising the temperature to a high degree. Then cold water was poured down the shaft. This sudden drop in temperature on one part of the rock caused it to crack violently and break away from rock beneath which was still extremely hot..
The miners than began to use picks to break this rock up into pieces that would fit into a large wooden container which was hauled up to the surface. This vessel was also used to transport the diggers down the shaft and back up after the day's work.
This work was hazardous in many ways. The shafts could be over 100ft (33m) deep so the miners often worked in near total darkness, the only light being from an oil lamp the miner carried. Miners lives were short. As they dug, choking rock dust swirled around them getting into their lungs and gradually building up deposits. This in turn led to fatal chest problems. Many fell on the uneven surface and broke limbs and there was always the danger of the shaft collapsing and burying them under hundreds of tons of rock. Added to this was the danger of flooding from porous rock seeping water into the shaft. Other slaves would send down buckets on ropes to collect this water and bring it to the surface for disposal a safe distance away.
Once on the surface the rocks would be placed on to the floor and pummeled with heavy sledgehammers until they were broken into small fragments. This pieces were then placed into a large wooden container and water would be poured over them. The rocks would then be removed leaving the gold dust and nuggets which would be removed and stored. Goldsmiths would melt the gold in a furnace and pout it into ingots which were stamped with the mark or name of the company. Most of these bars were transported to Rome where they were added to the treasury or used in the manufacture of coins.
Poznatky ke geologii oblasti lze získat také v National Museum of Wales v Cardiffu, které rozhodně stojí za to navštívit.