The present invention comprises a method and a system of collection and analysis for in situ determination of concentrations of minerals in granular material originating from a shaft under excavation, in a continuous, non-intrusive manner in real time. According to the present invention granular material collected passes to a granular material collector, subsequently entering a reading module which determines the concentration of different materials by spectroscopic methods. The granular material collected comes from drilling dust which rises along a boring tool of an excavating bit. The concentration data of different minerals in the granular material being analysed at a given moment may be processed and transmitted to establish and/or correct logistic and operational procedures such as, for example, in an excavation or in an overall process wherein it is set.