The Riotinto-Nerva mining basin is a Spanish mining area located in the northeast of the province of Huelva (Andalusia), which has its main population centers in the municipalities of El Campillo, Minas de Riotinto and Nerva, in the region of the Cuenca Minera. It is also part of the Iberian Pyrite Belt.
Historically, this area has been exploited for mining purposes, and a major industrial complex was established in contemporary times. Although there is evidence of this type of activity in the area during protohistoric times, it was not until Roman times when an organized exploitation of its deposits took place. After the activity of the mines was resumed in the Modern Age, the Riotinto basin experienced its peak between the end of the 19th century and the middle of the 20th century under the management of the British Rio Tinto Company Limited. A significant industrial and demographic boom took place during those years. Nowadays, the mineral extraction activity continues, mainly in the Cerro Colorado, although without reaching the production levels it had in the past.
The basin holds an extensive historical and industrial heritage as a result of the activities that took place during the Contemporary Age, especially those related to the British period. As a result, in recent decades various initiatives aimed at its preservation and use for tourism purposes were implemented. In 2005, the Riotinto-Nerva mining area was declared Bien de Interés Cultural with the category of Sitio histórico.
Characteristics The Riotinto-Nerva mining basin is located in the northeastern part of the province of Huelva, within the historical region of eastern Andévalo, at 418 meters above sea level. The basin has an approximate extension of 170 square kilometers. Like other deposits in southwestern Spain, the Riotinto-Nerva area is part of the Iberian pyrite belt. Because of this, it has important reserves of pyrite and chalcopyrite, minerals with multiple applications in the field of industry. The mining area is framed within the low mountain landscape that predominates in the Andévalo, with a relief of relatively smooth terrain - between 700 and 500 meters. In terms of physical geography, there are hills, mountains, and eroded areas. Notably, the physiognomy of this area has been considerably altered throughout history as a result of mining activity.
The Riotinto complex was formed by several polymetallic masses extending over an area of 4 square kilometers and hosting a total of 500 Mt (megatonnes) of ore. The main formations identified are Filón Norte, Filón Sur, Masa Planes, Masa San Dionisio, and Masa San Antonio. The latter extends over the municipality of Nerva and, compared to others, is the most recent mineral formation (second half of the 20th century). The presence of the Peña del Hierro mass also stood out in Nerva.
History
From Antiquity to the Middle Ages The Riotinto mines have been described as "one of the most important mining districts" of Antiquity. There is evidence of the existence of mining activities in the area of the current basin during the Copper Age and the Bronze Age, although these would not reach a greater relevance until several centuries later. The isotopic analysis at Riotinto have revealed that there was already considerable activity since at least 366 BC, while the oldest remains of mining operations and human settlements have been found in the area of Filón Norte. The minerals may have had two possible export routes: a first route, that reached the Guadalquivir River through a complex mountain road; and a second, through the Tinto River.
Although the information is limited, there is also physical evidence indicating that in Roman times several mines in the Riotinto area were in operation. It was between the 2nd century BC and 2nd century AD when mining activity in the area reached its peak, especially after the reign of Augustus. The Romans carried out the extraction labors by means of a network of underground galleries and complex systems of hydropowered scoopwheels to move the water inside. The working conditions in the galleries were very harsh for the miners - mostly slaves - due to dust, high humidity, poor lighting and high temperatures. Different contemporary studies have pointed out that silver was the metal of greatest production during the High Roman Empire, Riotinto being among the best silver mines of Antiquity. From the Augustus era, the extraction of copper also reached a great relevance.
The Romans erected numerous buildings in the area to support mining and metallurgical activities, such as furnaces and foundries, as well as roads to facilitate the transit of goods. The current Corta del Lago housed the main Roman settlement in the area, which classical sources identify as Urion or Urium. Likewise, there are several necropolises (Huerta de la Cana, La Dehesa) related to the High Roman Empire. The Riotinto mines remained active until the last quarter of 2 AC, when the deposits of the Iberian pyritic belt declined in favor of the then booming mines of Dacia or Britannia.
The metallurgical work carried out in Roman times left a large quantity of slag and considerably altered the physiognomy of the territory. Centuries later, much of this slag would be reused for various purposes, such as flux material in metallurgical processes. Many of the archaeological remains from the Roman period would be recovered and preserved from the 19th century onwards as a result of the work carried out by British engineers. However, the first findings of this type were made by Spaniards in the middle of the 18th century.In 1762, exploration work was carried out in the Roman galleries of what is now the municipality of Nerva.— During the medieval era, mining production in the Riotinto area was not significant. In the Islamic era, most work was focused on the exploitation of copper sulfates and iron sulfate.
Reactivation in the Early modern period The possibility of reactivating the exploitation of the Riotinto mines was considered during the 16th century, under the reign of Philip II. The deposits were owned by the Spanish Crown at that time. However, this project was eventually abandoned in favor of the Guadalcanal mines (Seville), which offered better prospects. The American mines were of greater interest to the authorities, in contrast to those of Huelva, which were considered to be exhausted after their intense exploitation in Roman times.
In the early 18th century, mining interest in this area was reborn. In 1725, the Swede Liebert Wolters Vonsiohielm was granted a lease by the Crown to exploit the Riotinto deposits for a period of thirty years. Wolters proceeded first to drain the old Roman galleries. After his death in 1727, the management of the mines passed into the hands of his nephew, Samuel Tiquet, and a Spanish partner. The mining works were focused on Filón Sur. After Tiquet's death, the Spanish partner, Francisco Thomas Sanz, took over the management of the mines, under whose direction the mines reached high production rates. Due to the influence of the mining works, the town of Riotinto was also established during this period, next to Filón Sur.
The Riotinto mines were abandoned and inactive during the War of Independence due to the difficulties that the country underwent in those years. In 1823, after a trip to the area by the engineer Fausto Elhuyar, the facilities were rehabilitated and work was resumed. Between 1829 and 1849, the Marquess of Remisa leased the exploitation of the deposits; many irregularities took place during this period.The engineers Fernando Caravantes and Francisco de Sales, who visited the Riotinto mines in 1840 and 1841, reported that the area's resources were being plundered under the management of the Marquis of Remisa. The extraction activities were generating a high risk of future landslides as well as causing large-scale local deforestation to obtain fuel for the furnaces and smelters. This was jeopardizing the future and viability of the operation.— After 1849, the Spanish Royal Treasury resumed direct management of the deposits. Influenced by the industrial revolution that was taking place, the Riotinto mines began to face problems due to the lack of infrastructure and technology, which prevented an adequate exploitation. However, in the middle of the 19th century, the poor financial situation of the Spanish State made it impossible for it to make optimal use of its mining properties.
British phase: the peak years By the middle of the 19th century, the Riotinto mines aroused the interest of international capital, in a context in which the industrial take-off that some European countries were experiencing had increased the need for access to new sources of raw materials. Since the public treasury was going through a state of crisis, the possibility of the State selling these deposits had already been considered. After the triumph of the revolution of 1868 and the political change that followed, in March 1870 the minister Laureano Figuerola presented a project for the sale of the Riotinto mines to the Cortes. However, the proceedings were delayed for several years.
In 1873, the House of Rothschild acquired the ownership of the deposits from the government of the First Republic, which was transferred months later to the newly created Rio Tinto Company Limited (RTC), of British origin. The new owner of the basin started a much more intense exploitation. Mining work was initially concentrated in "La Mina" deposit (or "Filón Sur"), although by 1881, the operations had already been expanded to other parts of the area. Among the minerals extracted from Riotinto were copper and pyrite. RTC built several industries for the mining-metallurgical treatment, which included ore washing plants, factories, smelting, power plants, warehouses, etc. By the early 20th century, the Zarandas-Naya area was the main center for the processing of ore coming from the deposits of the basin.
As the mining operations progressed, a series of main exploitations emerged in the basin, including Corta Atalaya, Filón Sur, Filón Norte and Corta Peña del Hierro. Some of them constituted mining complexes that were composed of several deposits. An important mining-industrial complex was also formed around the towns of Riotinto and Nerva, which grew in size and number of inhabitants during those years. Within a short time, the region became one of the most important mining areas in Spain. In addition, under British management, the Riotinto mines became "a world reference".
In order to improve the access to this network of mines and industrial facilities, the RTC built a narrow-gauge railroad, inaugurated in 1875 and with a network of nearly 360 kilometers between the main track and the various branches. Minerals were also transported through this railway line to the port of Huelva, from where they were shipped abroad. The intense traffic led the RTC to build an important ore deposit near Huelva, called "Polvorín".