Asselberghs tells us in 1924 "This slate quarry, that was opened around 1884, is today the headquarters of the Herbeumont Great Slate Quarries Company. There is a shaft dug 100m deep into the face of the fault following the course of the gradient. The operation consists of a dozen chambers spread over three levels. On average, the chambers are 30 metres long and 18 to 20 metres high. One chamber is 37.5 metres long. Each level is separated by veins, whose gradient, unlike in the quarry at Neufchâteau, is not perpendicular to the surface. The gradient of the veins is more acute, forming an angle of 60° with the horizontal. This arrangement has implications for the method of extraction used in the chambers, in that the part next to the wall of one chamber is accessed by a gallery at the same level, while the part next to the roof is worked on by the extended gallery at a higher level. The usable vein is 40 to 50 metres deep. It is about 200m long. The bed of rock runs N 83&d... [Detail]