Detail of a marine origin sandstone from Les Marcetes (Manresa). The crossing layers are due to the movement of the sand by the sea weaves. Usually, thin layers less than 1 cm depth can be seen in sandstone stratums. Sandstones are detrital rocks that result from the cementation of sands which, in their turn, are generally included in a matrix of smaller size particles. The sands are fragments of minerals or rocks with diameters between 2 and 1/16 mm. The cement of the sandstones in the district of Bages is calcium carbonate.
Sandstones of both continental and marine sources are common all around the region. Often, iron oxides dye in red, rusty color the sandstones of continental origin. Sandstones are found whether in thin layers into other rocks (mainly mudstones) or in big, homogeneous packs that usually have been or are currently being exploited. Sandstones were used in most of the ancient buildings of the area because their availability and ease to shape. [photo Florenci Vallès]