Complete surviving ensemble of the puits N°6 de l'Ermitage at Trélazé, with its 1932 metal headframe, steam extraction engine, changing rooms, and boiler house all intact.
The puits N°6 de l'Ermitage at Trélazé, Maine-et-Loire, is the best-preserved of the surviving shafts from the ardoisières of Trélazé, retaining its complete surface ensemble including its metal headframe of 1932, the steam extraction engine building, the changing rooms (vestiaires), and the boiler house. The puits N°6 de l'Ermitage served as the ventilation shaft and safety backup for the adjacent puits N°7 de Monthibert during the final decades of extraction at the Grands-Carreaux ardoisière, the last underground slate mine in France. The ardoisières of Trélazé, exploited in recorded form since 1406, were consolidated under the Commission des Ardoisières d'Angers from 1891.
Underground extraction became the sole mode of working in 1899. The second electric power installation for the Grands Carreaux and Hermitage quarries was installed in 1882. The Ardoisières d'Angers closed definitively on 29 March 2014.
The complete ensemble of the puits N°6 de l'Ermitage was identified as surviving intact at the time of closure; the other industrial buildings of the Grands-Carreaux carreau were largely razed.
The puits N°6 de l'Ermitage stands on the Hermitage sector of the Grands-Carreaux ardoisière at Trélazé. The ardoisières of Trélazé have deep roots: open-cast working is recorded at Tire-Poche from 1406, the first quarry at Champ-Robert from the mid-fifteenth century, and the site at Terre-Rouge from a comparable period. By 1678 the philosopher John Locke described the quarries in detail, and by 1762 over 1,200 workers were employed.
From the early nineteenth century the grand exploitants progressively consolidated, the Commission des Ardoisières d'Angers being formed in 1891, which became the Société des Ardoisières d'Angers in 1963. In 1882 a second electric power installation was established to serve the Grands Carreaux and Hermitage quarries. When the last open-cast quarries closed in 1899, extraction became entirely underground via shafts.
The first metal headframe in the entire Trélazé basin was installed at the puits N°6 de Grand'Maison in 1909-1910. The metal headframe now standing at the puits N°6 de l'Ermitage dates from 1932. The winding mechanism of the puits N°6 is that of a steam extraction engine, with the associated boiler house forming part of the intact surface ensemble.
The configuration of the headframe at the puits N°6 shows a characteristic technical detail: the faux-carré is offset from the poussards because the original timber cage-frame (carrée en bois) had collapsed, requiring the backfilling of the original open-cast workings, the insertion of new cuvelage in the shaft, and the installation of the present metal headframe. The puits N°6 de l'Ermitage served as the ventilation and safety shaft for the puits N°7 de Monthibert throughout the final productive period of the Grands-Carreaux ardoisière. As puits N°7 deepened to reach −520 metres and centralised all production and personnel movement for the Grands-Carreaux, puits N°6 provided the complementary ventilation circuit and emergency egress.
From 2009 the Fresnais quarry was closed, leaving the Grands-Carreaux alone in production. By 2007 the Ardoisières d'Angers employed 220 workers, including 60 underground, with annual production of 9,000 tonnes from the Grands-Carreaux puits. The closure was announced on 25 November 2013 and became effective on 29 March 2014, the Imerys group having concluded that the gisement was definitively exhausted.
After closure, the carreau de Monthibert was integrally levelled and most industrial buildings demolished. The puits N°6 de l'Ermitage was identified as the most complete surviving surface ensemble at Trélazé, retaining the metal headframe, the steam extraction engine building, the vestiaires, and the chaudière (boiler house). Eight chevalements had stood at the height of extraction; six survive.
The site of the former ardoisières has been classified as a zone naturelle d'intérêt écologique, faunistique et floristique.