Former mine shaft of the São João orebody within the Aljustrel complex, part of a nationally classified Iberian Pyrite Belt mining site.
Poço Nº 1 is a mine shaft associated with the São João deposit at Aljustrel, a multi-orebody sulphide mining complex in the Iberian Pyrite Belt of the Portuguese Alentejo. The shaft was sunk in the late 1930s to replace the earlier wooden-malacate Poço Jacobs, and served as the principal winding access to the São João mine during the 1950s and 1960s. Its metal-framed malacate is among the winding structures preserved at Aljustrel, where the wider complex — encompassing the Algares, Moinho, Feitais, Estação and São João deposits — was classified as a National Monument in 1982.
The São João area was exploited in antiquity by the Romans and again in modern times from the mid-19th century. The site today forms part of the Parque Mineiro de Aljustrel, opened in December 2023, and can be visited along a 12 km mining heritage trail. Pyrite, copper, zinc, lead, silver and gold were all extracted from the Aljustrel field at various points in its history.
Mineral extraction at Aljustrel extends to the Chalcolithic period of the third millennium BC. By the Roman period a settlement known as Vipasca had formed in the area of the Algares and São João deposits, from which copper and other metals were worked intensively between approximately the 1st and 4th centuries AD. Slag deposits from the Roman period are estimated at around 450,000 tonnes. Following the end of Roman occupation mining lapsed for centuries, returning to notice in the Foral of 1252, when the Order of Santiago da Espada reserved its income from the mine. A 16th-century regulatory document and a mid-16th-century royal record mentioning the pigment known as Azul de Aljustrel confirm sporadic exploitation before the modern era.
The first modern concession for the São João mine was granted in 1845 to Sebastião de Gargamala, marking the establishment of the first extraction shaft and the first mining workers' quarter at the site. The concession passed briefly to the Lusitanian Mining Company, which carried out little work, then transferred to the Companhia de Mineração Transtagana. This company operated for about fifteen years, undertaking large-scale production and constructing a metallurgical establishment at Herdade das Pedras Brancas, with roasting and cementation fields and a railway link to the station at Figueirinha. The first malacates at Aljustrel, built around the mid-19th century, were driven by mules; later wooden-framed versions used steam engines fuelled by wood or coal, and subsequently poor-gas motors. Electric-motor-driven steel-framed malacates followed in later decades.
In 1867 the Companhia de Mineração Transtagana was succeeded by a company formed that year, which took charge of the São João do Deserto and Algares mines. Operations grew substantially, aided by the arrival of the railway at Beja in 1864. By the late 19th century control passed through a banking house associated with Belgian capital, resulting in the formation of the Société Anonyme Belge des Mines d'Aljustrel. The name of the principal shaft at the Algares sector — originally called Eyben after the first Belgian administrator — reflects this period.
The Minas de Aljustrel employed around two thousand workers at their peak, leading to the creation of company-built workers' quarters including those of São João, Valdoca, Algares, Santa Bárbara and Plano. The complex reached depths of 425 metres. Compressed-air-powered tools were introduced in 1924, and the Central de Compressores de Algares was constructed in 1952, housing two new compressors and one transferred from the earlier plant. A second compressor station, the Moinho plant, was built in the 1960s as a reserve facility and was deactivated in 1992. Hydraulic tools replaced compressed-air equipment in the 1980s.
Sinking of Poço Nº 1 of the São João mine began in the late 1930s. The shaft operated through the 1950s and 1960s, replacing the older Poço Jacobs, which had been served by a wooden malacate and stood immediately adjacent to a large open-cast working. By June 1973 the operating company was reconstituted as Pirites Alentejanas, SARL, with a 50% state stake, 40% held by CUF, and 10% by Belgian interests. Following the nationalisation programme of 1975, the state held 90% of the company. Production was suspended in October 2008 owing to falling zinc and lead prices, and the company subsequently changed its designation to Almina - Minas do Alentejo.
The Minas de Aljustrel were classified as a National Monument in 1982. In December 2023 the Parque Mineiro de Aljustrel opened, incorporating a reception and interpretation centre beside the Malacate Viana, a restored underground gallery, an extensive network of cycleways and boardwalks, and requalified miners' quarters. The surviving metalframe malacates — including those of Vipasca, Viana and São João do Deserto — continue to mark the landscape of the mining complex.