Closed Asturian coal shaft at Ciaño, Langreo, with surviving 1940 welded-steel headframe and 1920s pithead buildings listed in the regional heritage inventory.
Pozo María Luisa, situated at Ciaño in the concejo of Langreo, was one of the most emblematic bituminous coal mines in Asturias. The yacimiento was first worked from 1858 through the Socavón de María Luisa by the Unión Hullera de Santa Ana, a French-capitalised company, and passed to the Sociedad Unión Hullera y Metalúrgica de Asturias in 1886. Shaft sinking began in 1918 and the pozo reached full production in 1942 under the Sociedad Metalúrgica Duro-Felguera.
It was integrated into Hunosa in 1967 and closed on 31 December 2016 as the last mine in Langreo to cease extraction, after 158 years of activity on the site. A firedamp explosion on 14 July 1949 killed seventeen miners. The headframe, dating to 1940 and the first in Spain built using welded-steel construction, the loading bay of 1941, and two large 1920s pithead buildings are listed in the Inventario del Patrimonio Cultural de Asturias.
The shaft reached 505 metres in depth across ten working levels.
The coal seams at Ciaño, in the concejo of Langreo, were first exploited from 1858 through the Socavón de María Luisa, a horizontal drift entry, by the Unión Hullera de Santa Ana, a company backed by French capital. In 1869 the working passed to the Sociedad Carbones de María Luisa, and in 1886 to the Sociedad Unión Hullera y Metalúrgica de Asturias, founded in 1884 by the engineer Luis Adaro y Magro through a merger of several companies. In the early twentieth century the Sociedad Unión Hullera y Metalúrgica de Asturias was absorbed into the Sociedad Metalúrgica Duro-Felguera, which undertook the sinking of the present vertical shaft. Shaft sinking began in 1918, but the pozo did not reach full operational capacity until 1942, after the Spanish Civil War. During the 1920s Duro-Felguera constructed two large pithead buildings — the offices and the washhouse — in a style consistent with their other installations in the Langreo valley, with red-brick cladding and crenellated cornicing.
The first headframe at the shaft was constructed around 1940 and was the first headframe in Spain to be built using welded-steel construction, marking a significant technical advance. The loading bay was constructed in 1941 with a structure of rolled-steel sections clad in metal sheeting and fibre cement. The pozo reached a depth of 505 metres across ten working levels.
On 14 July 1949 a firedamp explosion killed seventeen miners at the shaft. The event gave rise to an adaptation of the traditional Asturian song "Santa Bárbara bendita," which became widely known as "En el pozo María Luisa" and has since served as an informal anthem in the mining valleys of Asturias and León.
In 1967 the shaft was integrated into Hunosa along with the other mining assets of Duro-Felguera. In 1973 a Koepe winding pulley was installed on the headframe as part of a modernisation of the extraction system. King Juan Carlos I and Queen Sofía descended the mine in 1976, wearing miners' equipment, an event that attracted wide media attention. The then Prime Minister Adolfo Suárez also visited the shaft at a later date. In 2008 a second Koepe winding pulley, sourced from the Pozo Siero II, was incorporated, requiring the construction of a new winding engine house and the renewal of the shaft guides. These modifications were inaugurated on 24 September 2009 at a cost of 6.5 million euros. The coal washery at the site was demolished in 2002. The closure of the Pozo Sotón at the end of 2014 led to the transfer of its personnel and activity to María Luisa.
The shaft ceased coal extraction on 31 December 2016, the last mine in Langreo and the end of 158 years of coal working on the site. The headframe and loading bay are listed in the Inventario del Patrimonio Cultural de Asturias. The 1920s offices and washhouse buildings also survive at the site, along with the original bocamina of 1897 from the earlier Grupo María Luisa mountain mining phase, a brick ventilation chimney of 1900, compressors and lamp room of 1936, and the bocamina del tercer piso of 1950 at El Carbayal, which has been converted into a chapel.