Continental mudstones with the erosion pattern called pothole in Sallent. Mudstones are detrital rocks made up of less than 1/16 mm diameter particles. If these fragments are coherent, then the rock is named siltstone in case of the particles are above 1/256 mm size or claystone in case of below 1/256 mm. If these fragments do not have enough coherence, then the rock is called silt and clay. The mudstones that contain 50% of calcium carbonate on average (35%-65% according to Vatan) are called loams. They're usually bluish color. The color of mudstones in the area of Bages changes from the bluish gray or yellowish of the sediments of marine origin, to the characteristic reddish of those sediment of continental origin which contain iron oxides.
The extraordinary hollow out of the morphology of Bages is a consequence of the scarce resistance in front of the erosion of the mudstones. Mudstone materials predominate in the farmed plains. Mudstones are used in the manufacture of ceramics and bricks for building purposes. [photo Marc Vilarmau]