crystals are disseminated in layers of marl rock belonging to the
Cretaceous (Weald), with a long lateral continuity which has promoted
the abundance of outcrops. In Navajún and within the "Ampliación
a Victoria”, there are three well known layers with pyrite,
called from lower to higher, first, second and third layers. The
thickness is variable, with an average of 2.5 meters. The mean formation
inclination is 15º and there are strong spatial variations
in terms of thickness, morphology and oxidation condition of pyrites.
The most important mining works have been made on the first level.