HISTORY of RIO TINTO MINES
Rio Tinto mines are part of the 230km-Iberian pyrite belt, extending from Aznalcollar near Seville to Aljustrel in Portugal. Pyrite is a mineral containing a combination of Sulphur, iron and copper, with a metallic lustre which lends it the name "fool's gold". At certain points this mining field showed surface signs of two other vividly-coloured copper minerals, bright green malachite and deep blue azurite, which must have attracted the curiosity of the area's prehistoric inhabitants.
The inhabitants of the area around the upper part of the Rio Tinto, in the first centuries of Roman rule, were a Celtic tribe called Turdetani who had intermingled with the northern Tartessians. These people probably provided much of the labour force at the mines when the Romans began to exploit their rich ores. The mining activities of the Romans at Rio Tinto in the first two centuries were clearly limited in extent.
In this period of the Roman Republic (up to 27BC), the state exercised ownership of the mines but let out claims to individuals or small prospector groups. No remains have been found from this period and the earliest Roman coin in Rio Tinto museum is Nerva (AD 96 to 98).
During the Roman Empire, cartels of bankers took over mining operations. Considerable capital investment was required in order to get below the veins on the surface down to the deeper deposits. The mining industry began to be dominated by syndicates about Vespasian's time (AD 69 to 96).
By this time, copper mines had been developed and soon surpassed all others in the entire Roman Empire.
The Roman method was to dig vertical shafts 75cm wide - circular in harder ground, and rectangular in softer ground - supported by linings of wooden planks. If an exploration was successful, galleries (horizontal tunnels) were constructed radiating out from the bottom of the shaft. The internal galleries were seldom more than 60cm across and 1m high, with slightly arched tops and a drainage channel cut into the floor. The mined ores were dragged along by men or boys in grass baskets. Rich seams required more workers and made it worthwhile to open the galleries up to 1.60m high and 1.30m wide.
Transportation of the ores and debris from the face was by small baskets of esparto grass, dragged by their handles or carried on the back along galleries and up shafts either carried by ladder or lifted by ropes.
The galleries were dimly lit at intervals by the provision of terracotta lamps on shelves cut into the rock.
Gallery rooves were supported by wooden props of oak from the nearby forest.
Ventilation to the deeper galleries was a problem for the Romans, as when damp air came into contact with the sulphur in the rock, sulphur dioxide and hydrogen sulphide was produced. The Romans dug additional air shafts between the tunnels and the surface and probably lit fires to greater draughts and increase the circulation.
Drainage was the Romans' biggest problem. Horizontal audits into the hillside were inclined slightly upwards, and small channels were cut into the floors of galleries; drainage "adits" (horizontal tunnels) were also constructed.
Water that collected in the bottom of the entrance shaft was scooped into buckets which were lifted on ropes up the shafts. Where the water was too deep, elaborate 5m wooden water wheels with bronze axels raised the water. A total of 30 water wheels have been found at Rio Tinto, including a nest of 16 wheels in pairs at eight levels, capable of lifting the water a total of 35m high.
Mine workers under Romans were divided into three classes: free citizens, slaves and criminals. Pliny claimed the mines in Betica (modern-day Andalucia) had 20,000 slaves, of which around half would have worked in Rio Tinto.
Following the adoption of Christianity by Emperor Constantine (AD 306 - 37) numbers decreased. Free citizens were employed for skilled work. Historian Ernest Deligny has argued that working productively while exposed to constant danger at the rock face would have required skill and the self-discipline that could only be expected of a free man.
You can get an idea of what conditions were like in the museum which has an excellent reconstruction of a Roman mine, including a water wheel.
The Romans treated the ores mined in furnaces. Dr B Rotheburg of Tel Aviv University located about 20 in 1974. The furnaces were small, generally formed by excavation into the solid rock with a semicircular wall about 2m high. The charge (a mining expression for the quantity of material loaded into the furnace in a single batch) was only 100 to 200kg of ore, and on the stone base were placed alternate layers of charcoal and ore, heaped over with clay and earth. When ignited air was blasted into the furnace with leather bellows, eventually a mass of fused metal sank to the bottom. Further refinement was needed and silver was recovered using cupellation (primitive refining using a cupel, or funnel) with lead that had to be imported. To obtain copper, the process was lengthy as the sulphide minerals and the products from smelting had to be roasted several times.
In 410 AD the Visigoths sacked Rome and the Romans withdrew from the Iberian peninsular.
By this time the Rio Tinto ancient slag amounted to 16m tons, two thirds of that found in the entire pyrite belt.
VISIGOTHS AND MOORS
After hundreds of years of activity using impressive mining and smelting techniques, the region was inexplicably abandoned after the Roman era. In Visigothic times there was limited mining activity, and during the Moorish era, some surface work was carried out. The main evidence of activity in Moorish times is the town of Niebla, with its massive fortified walls, built using wealth partly from granting permits.
Read more about History of Rio Tinto Mines - Middle ages
Thanks to David Avery and RTZ for their 1974 book Not on Queen Victoria's Birthday, which is the definitive history of the Rio Tinto Mines. Thanks to William Giles Nash for his 1910 book The Rio Tinto Mine: Its History And Romance, from which much of this information was sourced. You can buy a second-hand copy of Avery's book, and a scanned on demand reprint of Nash's book, from Amazon. (Click on books in right hand margin of this page)