Definition: Slate schist

Slate schists are the result of tectonic movements during the Carboniferous period (300 million years ago), when the clay sediments of the time were transformed by high pressures and temperatures. These schists are all the more tender because the original sediments were clayey. Schist is often associated with other rocks and forms specific types of soil: sandstone schist and blackish, more clayey than average, ampelitic schist soils; schist and stony, ochre marl soils, which are less acidic than average; soils of schist, limestone and dolomite, which are less acidic and more clayey than average; or soils of sandstone schist and magmatic rocks, which are very poor, hard and acidic.