“Aurum” is Latin for gold, and it’s been treated as an object of great value for tens of thousands of years. But let’s just go back 2,000 years, the early period of the Roman Empire after Julius Caesar was murdered. His eventual heir, Caesar Augustus, established a fairly stable realm – the Pax Romana – that lasted well beyond his lifetime. Within that realm was Hispania, the outlying peninsula that now contains Spain and Portugal. In the northwestern mountains of Hispania they found gold, and since Augustus and his successors needed gold to achieve a transformation of Rome, he chose to exploit the gold in those mountains. For the next 250 years, Roman engineers, freemen workers and slaves, plus soldiers and others expended massive efforts – possibly incomprehensible efforts – to derive tens of tons of gold from those mountains. These remote Spanish mountains became the single largest source of gold during the Roman empire period. And it’s where I find myself on Day 2 of the Camino Invierno.
The mountains are called Las Medulas, and they’re preserved now as a UNESCO World Heritage site. Picture this, until the Romans determined that there was plentiful gold, especially concentrated at the lower strata, far underneath multiple sedimentary layers, these mountains must’ve looked like the rest of the northwestern region of the peninsula… tall, softly rounded and most likely lush with vegetation. Water was plentiful, especially from the nearby river, now known as the Ribas Sil, flowing from the peninsula’s northernmost mountains.
In order to reach the gold-rich lower layers, Roman engineers used the known principles of hydraulics – channeling the force of liquids to apply greatly magnified power – to erode the mountains, destroying the upper layers literally by washing them away. The Romans referred to this as “ruina montium” – destroying the mountains. Once this was done, water was also used to wash the exposed and excavated gold-rich layers, yielding massive quantities of this rare and valuable metal. The gold mined from these mountains went back to Rome where, among other uses, Augustus was establishing gold coins as a new medium of exchange for goods and labor. And it was labor, plus astounding use of physics and engineering – yes, 2000 years ago – that was applied to these mountains, and what we see today are the remnants of this work over 250 years of effort. You can think of it as intentional, and productive, erosion. A modern version of this is strip mining which uses mechanical force, and considerably less labor, to achieve the same results the Romans did.
Despite multiple efforts to get my head around how this was achieved, I still don’t understand it in satisfactory detail. But here it goes. Using the natural flow of water, long channels dug across the mountainsides, diverted the water from the river to higher elevations on the mountains where it was stored in reservoirs. Shafts and tunnels – referred to as galleries – were dug into the mountain itself. Try to Imagine the quantity and difficulty of labor in those times to dig such tunnels without the benefit of electricity or non-human power. When this digging was completed, the accumulated water that had been channeled out of the river and stored at high elevations was directed into the shafts, and from there into the tunnels. Ultimately the pressure from this water literally exploded the layers of rock into which the tunnels had been dug, leaving the gold-rich layers exposed for more conventional digging, crushing and washing until the shiny yellow metal was sifted out. Then add to this monumental task, that it was repeated, over and over again, on the same mountain as well as on other nearby mountains.
The remnants of these mountains are what astound us today at Las Medulas, all for the gold to feed an empire whose center was 1,300 miles away.
One thought on “Where the Romans got their Aurum.”
Wow! Have to admit I’d never heard of this advanced engineering being used by the Romans there. Way cool.