Open-air museum of slate extraction at Renazé, built around the surviving 22-metre Venot-Peslin headframe and its salle des machines, on the last quarry site in the Renazé basin, closed in 1975.
The puits de Longchamps at Renazé, Mayenne, is the slate extraction shaft that forms the centrepiece of the Musée de l'Ardoise et de la Géologie de Renazé, the principal heritage site for the basin's five centuries of slate working. The butte de Longchamps opened for extraction in 1890. In 1936 the Société des Ardoisières de l'Anjou sank the puits de Longchamp, designating it puits N°3.
The shaft was equipped with a trellised metal headframe of 22 metres, manufactured in 1926 by the Société Venot-Peslin d'Onnaing (Nord), originally installed at the Brémandière site at Trélazé, then dismantled and re-erected at Longchamp in 1941 by the établissements Jarry de Trélazé. The headframe's upper structure is decorated with croix de Saint-André balustrades and plein-cintre mouldings. The puits de Longchamp was the last shaft to close in the Renazé basin, in 1975.
From 1979, former miners began conservation work; the Musée de l'Ardoise et de la Géologie was inaugurated on 6 April 1991 and became a Musée de France in 2005.
The ardoisières of Renazé form the principal slate mining territory of the Mayenne department, extending across the communes of Renazé and Congrier. Slate extraction is attested at Congrier from at least 1450-1454, when a perrière and a commercial purchase of ardoise are documented. Two carrières opened at la Maillère and la Touche in 1650.
The principal industrial sites in the Renazé basin were la Gautrie, la Rivière, Saint-Aignan, Laubinière, la Touche, and Longchamps. In the nineteenth century the industry expanded rapidly: in 1857 Renazé counted 400 ardoisiers, and by 1920 the number had grown to 1,500. The apogee of production was between 1870 and 1920.
From the end of World War One, powerful industrial methods were introduced for more rational exploitation of the schiste beds. The Société des Ardoisières de l'Anjou, formed in 1894, was the principal operator, acquiring in 1895 the Ardoisière de l'Aubinière and in 1896 the Ardoisières de la Touche and du Fresne. The butte de Longchamps, at the location of the present museum, opened for extraction in 1890.
In 1936 the Société des Ardoisières de l'Anjou sank the puits de Longchamp, designated puits N°3. The shaft was equipped with a metal headframe of 22 metres, built in 1926 by the Société Venot-Peslin d'Onnaing, a prominent manufacturer of extraction machinery in northern France. The headframe had first been installed at the Brémandière site at Trélazé.
In 1941 it was dismantled and re-erected at Longchamp by the établissements Jarry de Trélazé. It is a structure of treillis beams; its upper section, where the winding sheaves are carried, features decorative croix de Saint-André balustrades and fine plein-cintre mouldings. It stands as one of the last surviving chevalements in the Renazé-Mayenne territory.
The bâtiment de la machine d'extraction, built in pan de fer and brick, houses the extraction machinery that remains on site. Up to 28 miners at a time descended in the cage. Blocks of schiste weighing two to three tonnes were raised.
The first mechanised extraction equipment arrived in 1920, reducing the heaviest underground labour. The deepest shaft in the Renazé basin, at Longchamps, reached 305 metres. By 1950 all quartiers of the Renazé basin were connected underground.
From the 1970s, enterprises progressively reduced export and then production of ardoise at Renazé. The last puits to close in the basin was the puits de Longchamp, in 1975. In 1975 the last miners of Renazé made their final ascent in the cage of the Longchamp headframe.
From 1979, a group of ardoisiers and local history enthusiasts began work to prevent the past from being forgotten. The Musée de l'Ardoise et de la Géologie was inaugurated on 6 April 1991 on the Longchamp butte site. The four hectares of butte, the headframe, the machine room, the preserved constructions, reconstructed tue-vents and cabanes, and the terril together constitute an authentic industrial heritage ensemble.
The museum became labelled Musée de France on 1 May 2005. The municipality of Renazé has subsequently undertaken the renovation of the puits N°3 headframe (puits de Longchamp), with a rehabilitation budget estimated at 191,646.70 euros. Three metal chevalements survive in the Renazé basin: the puits de Longchamps, the puits Saint-Aignan, and the puits de Laubinière.
