Crossing the zone from east to west we will find rocks that have undergone an increasing degree of metamorphism, that is to say, a progressive transformation due to have been buried every time to greater depth. In this series, the least transformed rocks are the slates that originally were clays and whose transformation consists fundamentally on the disposition in layers. 

The quartzites are another type of little transformed rocks originated from sands, whose grains appear welded by effect of the heat. The schists represent a greater degree of metamorphism but still the bands of the different minerals that form them can be observed. Gneisses present the greatest degree of metamorphism, in which the flows of almost fused minerals can be seen. The numerous quartz docks that cross all type of rocks filling up the fractures produced between rocks at the end of the metamorphic processes present a different origin.