A little bit of history...

Slate deposits are spread all over the world. Most of them do not have the same qualities because physical and chemical elements can be different from one area to the other.

The main slate basin which is exploited today is situated in Europe. It covers the provinces of Galicia, of Leon (north-west of Spain) and of Segovia (centre of Spain).

Slate is a sort of clay which was transformed by geological and seismic disruptions. As a result of erosion the sediments covered the bottom of oceans during the Primary era (more than 500 million years). This explains the presence of fossils and shells in the blocks of slate. These different sedimentary layers were affected by geological foldings, and the melting magma helped to modify the composition of clay (metamorphism). The shale-type slate appeared at that moment and the rock became fissionable. That is the reason why a block of slate is foliated and can be divided in thinner or thicker layers.

Video Presentation

View of a quarry

View of a cut block

View of a “labrador”

Some deposits are more than 500 million years old.

First slate was used for paving or tombstones around year 50 BC. Slate was first used for roofing in the 12th century. This use was not linked to any real standards at that time. The first real manufacturing standards appeared in 1950. 1958: NF P 32-301 standard 1977: DTU 4011 standard 1989: NF P 32-302 standard (it gives a quality classification of slate: class A, B or C)