(1) Carreau du Villaret: un carreau de mine regroupe l’ensemble des installations de surface nécessaires au fonctionnement d’une mine.

The use of gunpowder in mining has been marred by numerous accidents.
Powder magazines represented an even greater danger because of the quantities stored.
In small mines, a gallery built perpendicularly was used for storage. For larger mines, galleries were built especially for this purpose.
These galleries met special requirements as described below:
– Gallery of small dimensions
– Perpendicular storage gallery
– Decompression gallery in front of the storage gallery
– Vault-shaped gallery with an earth cover to contain a potential explosion.
– Access gallery in the form of a long corridor always with the aim of mitigating the damage produced by the blast effect due to the power of the deflagration.
The goal is to have a « decompression chamber » to mitigate the power of a deflagration.
Other elements are also important, such as ventilation to avoid excess humidity, which is harmful to powders.
Always with a safety objective, the metal parts are not made of iron but of bronze or tin in order to avoid any sparks. The person in charge of the powder magazine wears sandals and not studded clogs to avoid any sparks.
Lighting is also a critical point. You cannot use « naked lights »: a kerosene lamp with a protective grid is used to increase safety.
The galleries on level 12 also had their powder magazine located in a dedicated gallery at one end of the Villaret tile (1). It was located slightly above the tile and leaned against the mountain to comply with safety regulations.
Today there are only a few remains of concrete scattered on the ground which unfortunately do not allow us to precisely locate the position of the gallery. When the gallery was made safe in 1997, the two buildings that made it up on the outside were destroyed. The gallery was backfilled and covered with topsoil to erase all traces.

(1) Carreau du Villaret: a mine tile comprises all the surface installations necessary for the operation of a mine.