The effect of most usual kinds of mechanical treatment on marble, such as drilling, grinding, and polishing, has been systematically investigated with electron‐paramagnetic‐resonance (EPR) spectroscopy. Two different major effects have been observed: the decrease of Mn2+and the creation of several kinds of lattice defects. Drilling can cause a drop in the intensity of Mn2+by 50% and at the same time create a high concentration of lattice defects. The most characteristic is a defect, with a pair of peaks atg=2.0003 and 1.9997, created and filled with electrons simultaneously. The causes, nature, stability, and sensitivity to &ggr; irradiation of the two effects have been investigated. For the filling of the above defects with the mechanical action a model has been proposed. This involves another, EPR‐silent, defect that stores electrons by ionizing radiation during the geological age of marble and transfers a number of them by the mechanical treatment to the newly created defects. Another pair of defects (g=2.0069 andg=2.0059) has also been observed to be mechanically induced but not filled by the mechanical action. These are filled only by ionizing radiation. The reduction in the Mn2+signal is caused by the pressure exerted on the grains during the mechanical treatment, destroying the crystal symmetry and probably causing jumping out of Mn2+ions from their normal crystal symmetry sites. The decrease of the Mn2+sextet with drilling causes great concern to provenance studies of ancient marble artifacts that are based on the intensity of the Mn2+peaks. Finally, the polished surfaces of a number of ancient artifacts have been investigated for possible detection of absorbed radiation.