A petrographic description of natural stone is important not only for the purposes of petrographic classification but also in order to highlight features influencing its chemical, physical and mechanical behaviour. In the same way the determination of the stone’s origin could be necessary (e.g. in the case of restoration of historical monuments). It is therefore necessary to characterize the natural stones not only from the point of view of their mineral components and of their fabric and structure but also in terms of any features as: colour, presence of veins, of fossils, of discontinuities, etc.
To ensure that the petrographic classification is objective, the characterization of the material should, as far as possible, be quantitative.