PROMINAS, S.A. has been exploding for some years the varieties "Red Ayllon Quartzite and Grey Ayllon Quartzite" in the proximities of Riaza (Segovia). Seven years of geologic investigations showed the existence of an important volume of reserves. The method of operation, specifically developed and designed for this deposit, and a decided policy of investigation and development of systems of cut in operation bank, allows to extract regular blocks for its expedition and elaboration, which had not been possible by conventional methods....