Abandoned former Asturian coal shaft on the Langreo-Siero border, retaining a 52-metre concrete extraction tower of the 1970s and listed in the regional heritage inventory.
Antiguo Pozo Mosquitera, also known as Mosquitera I, was a bituminous coal shaft located on the administrative boundary between the concejos of Langreo and Siero, near El Entrego in San Martín del Rey Aurelio. Its origins lay in coal workings of the mid-nineteenth century, when the Coto Mosquitera was operated by the societies D'Eichtal, Marqués de Guadalmina, and Barón del Castillo de Chirel. The present shaft was sunk in 1927 by Duro Felguera, under the direction of mining engineer Luis Adaro, who introduced the first mechanical coal washery in Asturias at this site.
The shaft was deepened during the Civil War period and reopened with a major ceremony in May 1946. It was later integrated into Hunosa and modernised in 1977 with a 52-metre concrete extraction tower equipped with a Koepe winding system. A collapse in the mine's spoil heap in 1972 trapped twenty-six miners who were subsequently rescued.
On 22 December 1989 a fire in the seventh level killed four workers, and the shaft was closed. The fire took two years to extinguish. Most ancillary buildings were demolished in the 2010s.
The 1970s extraction tower and a nineteenth-century adit survive, and the site is listed in the Inventario del Patrimonio Cultural de Asturias.
Coal extraction in the area of Mosquitera began in the mid-nineteenth century through the Coto Mosquitera, operated at various times by the French banking house D'Eichtal and the Spanish noblemen the Marqués de Guadalmina and the Barón del Castillo de Chirel. A bocamina — a horizontal adit entry — from this period survives at the site. The Group Mosquitera concessions subsequently passed to the Unión Hullera y Metalúrgica de Asturias, which in 1906 was absorbed by the Sociedad Metalúrgica Duro Felguera.
In 1927 Duro Felguera sank the present vertical shaft, under the direction of the Madrid-born mining engineer Luis Adaro. Adaro installed at this site the first mechanical coal washery in Asturias, a technological advance of significance for the regional industry. The shaft was fitted with a lattice steel headframe and coplanar pulleys. The shaft reached a depth of 600 metres with a shaft diameter of 5.60 metres. During the period of the Civil War the shaft was deepened further. In May 1946 a large ceremonial inauguration of the expanded and modernised installations took place, attended by Francisco Franco, marking the entry of the shaft into its post-war productive phase.
The shaft continued under Duro Felguera ownership until the company's mining assets were integrated into the newly formed Hunosa. An undated integration into Hunosa as part of the Siero unit followed the reorganisations of the late 1960s, and the shaft was operated as part of the Unidad Siero of Hunosa. In 1977, as part of Hunosa's modernisation programme, the original lattice steel headframe was replaced by a new 52-metre concrete extraction tower. The tower housed internally a winding machine equipped with a bicable Koepe pulley, with two synchronised direct-coupled motors without a reducer, manufactured by EPD-Siemens of Germany. This tower was one of only a small number of such structures installed in the Nalón mining district.
In 1972 a collapse of the shaft's waste tip buried twenty-six miners in an incident that attracted widespread attention; all twenty-six were eventually rescued.
On 22 December 1989 a fire broke out in the seventh level of the shaft when a coal conveyor belt ignited. Temperatures inside the mine reached approximately 2,000 degrees Celsius as the fire spread to an exposed coal seam. Four workers employed by a subcontracted company, Exponor — Pedro Rodríguez García, Pedro Rodríguez Fernández, Alfredo Fernández Marcos, and Benito Suárez Orviz — died on the seventh level. Numerous other workers were injured; some escaped by breathing air taken from the tubes of pneumatic drills. Two further workers trapped on the seventh level, José Luis Rodríguez Moral and Roberto Lastra Martínez, survived and reached the surface. The fire was not fully extinguished until approximately two years after the incident. The shaft was formally sealed in July 1992. Following closure, the yacimiento of Mosquitera continued to be worked through the adjacent Pozo Pumarabule in Carbayín, which served as the extraction point for Mosquitera coal until 2005.
After formal closure, most of the ancillary installations — including the cargaderos connecting the shaft to the railway and the coal washery structures — were demolished during the 2010s. The 52-metre concrete extraction tower of 1977 remains standing at the site. A bocamina from the nineteenth century also survives. The site is currently in a state of abandonment. The Pozo Mosquitera is listed in the Inventario del Patrimonio Cultural de Asturias, conferring a recognised level of heritage protection on the surviving remains.