ROMAN MINING TECHNOLOGY
By Matthew V. Grieco
The ancient Romans were famed builders. They had sophisticated designs, superbly executed, and built to last. There is the iconic Colosseum, which continues to be used, although for events such as concerts and plays, not gladiatorial duels. The Romans also built an extensive network of paved roads (about 50,000 miles), with bridges, tunnels, and milestones, that allowed the swift movement of troops, traders, and travelers. Aqueducts, a good portion of which ran underground, carried fresh water (over 320 million gallons per day in Rome, alone) long distances to city residents, as well as public fountains and baths. Indoor plumbing and central heating brought a level of comfort that, after the fall of the Roman Empire, would not be known again until the 19th century. There were lavish villas in the country, multi-story apartment buildings in the cities, impressive basilicas for courts and markets, splendid temples (the domed Pantheon remains in pristine condition), spacious public fora, and triumphal monuments.
Not as widely known today, but also impressive, are the Roman accomplishments in the field of mining. Besides the archeological evidence, we have a number of original texts describing tools and techniques, such as the Natural History of Pliny the Elder (23-79 A.D.), On Architecture by Vitruvius (first century B.C.), the Geography of Strabo (64 B.C.–21 A.D.), and the World History of Diodorus Siculus (first century B.C.).
The Romans could locate underground veins of ore based on vegetation, soil, and the ground surface. For deep tunnels, they solved the problem of ventilation with parallel shafts, cross-cuts at different levels, and interconnecting galleries, which forced warm air from the mine to rise as cool air from the outside circulated in. Mechanical devices, operated with a hand crank or treadmill, were used to drain any underground water encountered.
Hammers, picks, and chisels were, of course, used. However, to bore galleries and remove some particularly hard metals, the Romans used a fire-setting technique that remained in use until the invention of dynamite. Wood fires were set next to the rock; when the rock became heated, vinegar or water was thrown against it, and the rapid drop in temperature fractured the rock.
The gold mining method was even more ingenious. The Romans dug tunnels under a mountain, then cut the bracing, and collapsed the mountain (the system was termed “ruina montium”). Channels were cut across the top of the collapsed mountain and sided with boards; a river or lake from a higher elevation was then diverted into the narrow channels. As loose soil was swept away, a type of bush placed along the channels at intervals caught any gold nuggets or flakes. The landscape of Las Medulas in northwestern Spain, the Romans’ largest gold mine, still bears witness to the ruina montium process.