On the 1st picture, a layer of limestone in Els Tres Salts, in the river Llobregat (Sant Fruitós de Bages), in a high water day. The water erodes the limestone and slowly pushes it back. The layer on top is a massive, fine limestone whilst the layer below is a reef limestone.
On the 2nd picture, the usual shell like fracture of the massive limestone. This pattern is repeated in most of fine grain, homogeneous rocks as chert and obsidian -a natural glass. Artificial glasses break in shell shape as well; it is obvious at the bottoms of champagne bottles.
Limestone is a calcareous rock made of mainly calcium carbonate. The most frequent limestones in Bages are arranged in really resistant to the erosion layers. They come from either marine as the one in Els Tres Salts– or lake origin. Nowadays limestones are mined in quarries as a material for building while, in the past they were used to obtain lime. Marine limestones of Bages contain a lot of macrofossils because they were sourced in reefs.
[photos Florenci Vallès]