Rock type: detrital sedimentary.

Age: about 250 million years. Triassic period (Lower Triassic, Facies Buntsandstein).

Characteristics: composed of fine sand particles (quartz, and brilliant minerals from the mica family and iron minerals). The surface of the blocks holds the structures called Ripple marks and a slickenside.

Formation environment: alluvial plain area

Uses: building materials.

Origin of the block: Xerallo, Sarroca de Bellera (Pallars Jussà).