Rock type: low-grade metamorphic.

Age: about 460 million years. Ordovician period.

Characteristics: alternation of millimeter-thick layers of sandstone of light-colored sandstone and dark-colored clays, which give it a banded appearance. The assembly is deformed by folds, at small and large scale, and is affected by foliation or cleavage planes.

Formation environment: originally formed from mud and sand at the bottom of the ocean and later affected by metamorphism at medium depths within the Earth's crust, forming the slate.

Uses: construction materials, jetties and pier and to make roof tiles.

Origin of the block: Roní, Rialp (Pallars Sobirà).