Mina Peña del Hierro — Pozo Maestro Nerva · Andalucía · Spain

The mine of Peña del Hierro stands within the municipality of Nerva in the province of Huelva, located in the Riotinto-Nerva mining basin and forming part of the Iberian Pyritic Belt. There is documented evidence of mining in the area during the Roman period, though the main ancient workings were concentrated in what is now the municipality of Minas de Riotinto.

The first systematic modern exploitation of the Peña del Hierro deposit began in 1853 when Agapito Artaloitia initiated extraction. A year later the mine passed to the Spanish-capital company Nuestra Señora de los Reyes, which carried out underground extraction until 1866, when activity was suspended. During this phase a total of 198,383 tonnes of mineral were extracted.

The mine was subsequently acquired by The Peninsular Copper Company, a foreign-capital enterprise that worked the deposit between 1883 and 1900, introducing open-cast extraction through the corta system from 1883. This company extracted 286,811 tonnes before ceasing operations in 1900 upon the dissolution of the company.

In 1901 The Peña Copper Mines Company Limited was constituted as a British-capital enterprise and took possession of the mine. Under this company the exploitation of the deposits reached its zenith. Between 1901 and 1955 a total of 3,992,780 tonnes of minerals were extracted. In 1904 the company constructed the Pozo Maestro — a vertical underground shaft reaching a depth of 125 metres — and erected over it the malacate, a wooden winding frame built for ore hoisting. The malacate carried a cage for ore wagons of 1.4 tonnes capacity and was originally powered by a steam engine. In 1936 this steam engine was replaced by an electric motor of 120 kW. For underground drainage, three anti-acid pumps were installed at levels 6, 11, and 12 of the shaft.

Around the Pozo Maestro a range of supporting structures was established: a crushing plant, an ore hopper, mineral storage deposits, and an internal railway network for ore wagons connecting with the main railway complex at the mine. In 1914 The Peña Copper Mines Company Limited inaugurated its own narrow-gauge mineral railway to transport ore to the Guadalquivir river in the province of Sevilla, replacing an earlier connection to the Riotinto railway that had been in use since 1883. A mining settlement grew up around the installations, with a recorded population of 825 inhabitants in 1910, including the Casa de Dirección, a Casa de Huéspedes for visiting directors and engineers, and the San Carlos residential group for British staff. An electrical power plant was also built to supply the mining installations with energy.

The Galería Santa María — a 200-metre tunnel originally used to extract mineral from the corta — was in use until 1960. The mine also employed hydrometallurgical methods, constructing canaleos and a water supply network including a mine dam, several dykes, and two reservoirs, Tumbanales I and Tumbanales II.

In 1954 the mine was acquired by Spanish capital through the Compañía Nacional de Piritas (CONASA), which operated it from 1955 to 1960, extracting 270,583 tonnes. In 1960 extraction was abandoned due to the low price of pyrite on international markets making the operation unprofitable. The crushing plant, however, remained in service until 1966. Between 1966 and 1972 acid waters from Peña del Hierro were pumped to the cementation balsas of Filón Norte in the Riotinto mines. In 1972 Río Tinto Patiño (RTP) acquired the Peña del Hierro deposits, and in the same year the mining workings were officially closed and abandoned.

From 1987 the former mine passed into the assets of the Fundación Río Tinto para la Historia de la Minería y la Metalurgia, which has carried out the heritage rehabilitation of the complex. The original malacate had been dismantled in 1985 and the timber used for other purposes. In 2006 and 2007 the Fundación Río Tinto completed the construction of a full-scale reproduction of the original 1904 winding frame in its original location, built from the original plans and using timber of comparable characteristics to the original.

The Fundación Río Tinto opened the Peña del Hierro site to public tourism in 2004. The rehabilitation programme, carried out over more than ten years, included the restoration of the Galería Santa María for visitor access, the conversion of the former Grupo Pilones workshop building into a visitor reception centre, the rehabilitation of the machine room, and the restoration of a miners' house as an ethnographic exhibit. A fire in August 2018 damaged the Galería Santa María, which was restored and reopened within four months.

In 2005 the Peña del Hierro complex was declared a Bien de Interés Cultural (BIC) with the category of sitio histórico (historic site) by the Junta de Andalucía. Its environmental significance was recognised by its designation as a Paraje Natural Protegido (Protected Natural Area) between 2004 and 2005, and the adjacent Montera de Gossan was declared a Monumento Natural de Andalucía in 2010. In 2012 the complex received the higher designation of Zona Patrimonial — the maximum level of protection under Andalusian cultural heritage law. The site forms part of the Parque Minero de Riotinto, managed by the Fundación Río Tinto. By 2007 the Parque Minero was receiving 74,000 visitors per year at the Peña del Hierro component.