operations Pliny records that shafts were sunk through the soft surface earth which was supported by wooden props. The shafts were aimed to intersect gold channels or reefs which were hacked out and the ore was taken to the surface where it went through the familiar process of crushing, washing and burning in a furnace to produce a powder. This powder was then crushed further and heated again in the furnace, which Pliny describes as made of a white material like potter’s clay, whereupon gold was finally released. Where large rocks – often of flint – were brought down in the tunnelling process they were broken up with large 150 pound iron rams and wedges, and carried to the surface in baskets.
The most spectacular mining method used was where galleries were driven into mountains or hillsides using a chain mining system; miners worked from deep inside the mountain passing out the mined rock. Left behind was a pillar-supported gallery and the pillars were then part cut to weaken them. The mine was evacuated when a spotter on a nearby hill, who watched for the outside signs that the gallery was on the point of collapse, signalled the workers to leave. When the mountain finally collapsed huge quantities of loose, broken material could then be treated in an attempt to extract any gold trapped in the material. This was a somewhat hit-or-miss operation as gold could not be guaranteed at the end of the process – the Romans would have had some idea of the prospectivity of the mountain or hill for gold, but their geology was rudimentary.
The secret of the treatment process used was being able to bring large quantities of water to the site and then store it in a reservoir so that a strong but controlled stream of water could be brought to bear on the broken material. A complex patchwork of channels and wooden sluices were also constructed to carry water and slag away, and trap any released gold. The system and scale of the operation puts one in mind of the gold workings in California in the mid-19th century where hydraulic mining was pioneered. Certainly historians think tens of millions of tonnes of ore were mined by the Romans in the region.
The technologies the Romans used in their Spanish mines were also sophisticated, as they had to be when shafts were sometimes sunk several hundred feet in pursuit of rich ore. Because of the sometimes large quantities of water at depth, de-watering was often an insurmountable problem, but a screw pump was uncovered at the ancient Centenillo mine near Linares in Andalucia. The pump was designed by Archimedes based on a system he had observed being used on the Nile to raise water. The machine consisted of a screw within a wooden cylinder, which was turned by hand and foot, with the feet working peddles which turned the screw. The turning of the screw enabled water to rise slowly up the cylinder and when it reached the top the water was then directed away from the workings.
The gold mined for the Romans was used in two ways. The primary aim was to provide money in the form of coinage to lubricate the Roman economy and importantly to pay for Rome’s imperial ambitions as well as the empire itself. There is much evidence that the second main use of gold was as gold ornaments for the upper layers of society – gold plate and jewellery has been unearthed over the centuries by archaeologists.
Indeed, it is postulated that before the reign of Constantine there was a period when gold supplies being used for coin were under pressure because a rising percentage of gold was being diverted into fabrication for personal use. There is also a view that after Spain the only new sources of gold for the Empire came from mines in Dacia in the Carpathian region of the North Balkans, conquered by Trajan in the 2nd century AD. Over the next two centuries there appears to have been little in the way of additional gold found in the Empire and gold prices, having previously fallen, then strengthened a little. This encouraged the inflationary practice of debasing the coinage by clipping coins in circulation enabling additional coins to be minted without the imperial treasury having to purchase new (and more expensive gold) for the coins.
Pliny the Elder (23-79 AD)
Although the great Roman soldier and observer Pliny the Elder was not a mining man, his writings on mining operations that he visited across the Roman Empire, particularly Spain where he was a procurator responsible for mine administration, have created an invaluable record for posterity. The book in which they appear, Historia Naturalis, is in fact a comprehensive study of geography and nature in the Roman Empire, and the sections on metals and mining are just a small part of the work. However, they are one of the few sources of directly observed comments on mining techniques in the ancient world that have survived to this day.
Born Gaius Plinius Secundus in 23 AD in Como, northern Italy, Pliny’s family held equestrian status indicating that they had money and were deemed aristocrats or knights. Pliny received formal education in Rome where his tutor, Pomponius, who was one of Rome’s leading poets, provided Pliny with connections important to his future career. At the age of 21 he went to the Low Countries to serve as a military tribune, an administrative post, but soon became a military officer. For the next few years Pliny served in the Lower Rhine area where he saw active service under his old tutor Pomponius.
At this stage, around 50 AD, Pliny began to write books, which included a biography of Pomponius and a history of the Germanic Wars. He returned to Rome where he might have been expected to continue his career in public service. It was, however, the age of Nero and Pliny’s position as a serious historian did not fit into Nero’s increasingly debauched society. He wrote further books which did not attract positive comment and as Nero’s rule ended with the Emperor’s suicide, a vicious civil war broke out. Around that time Pliny’s brother-in-law died and Pliny took on the guardianship of his nephew Pliny the Younger.
Vespasian, whose son Titus was a great friend of Pliny’s, had taken up arms to press his claim to become emperor as the post-Nero situation became increasingly chaotic. Vespasian entered Rome as emperor in 69 AD and from that point on Pliny’s career took a major turn for the better as he assumed a number of important public posts as a procurator, which took him all over the Empire. One of the regions he visited was Spain, where his responsibilities included keeping an eye on the gold mines which had assumed a key role in the Empire’s finances. It was here that he made copious notes on the techniques of mining and treating gold at locations such as Las Medulas in Leon, observations which eventually were incorporated into the mining section of his Historia Naturalis. He was not remotely a gold bull, however, as he believed that it merely played on man’s natural greed. He also made observations about silver mining, base metal (including lead) mining and even diamonds. The Historia also contained sections covering the use of metals in what we would now call manufacturing.
Pliny’s career continued with his appointment as prefect for the Roman navy in the western Mediterranean and it was during this phase of his life that Historia Naturalis was completed and published in 77 AD. In August 79 AD Pliny was holidaying with his sister and Pliny the Younger in Misenum when Mount Vesuvius erupted. Pliny ordered a fleet of ships, which he commanded, to set sail to rescue those who had escaped the disaster and were gathered on the shore outside Pompeii. He, unfortunately, had to spend the night ashore and in the morning was found dead overcome by the sulphurous fumes from Vesuvius.
The only book of Pliny’s to have survived is Historia Naturalis. Whilst archaeologists have done much work on ancient mining sites around the world and in so doing have provided much useful information on mining construction and techniques, Pliny’s observations are the real thing. They reveal the relatively sophisticated mining methods of the Romans, including the use of hydraulic (water pressure) style mining 1700 years before it was introduced into 19th century mining. As such Pliny’s work holds an invaluable place in the study of the mining industry’s historic development.
The site today of the Las Medulas gold mine in Leon, Spain which was mined in Roman times from the first century AD
Source: Rafael Ibanez Fernandez
Rome’s
