Silicon crystals were abraded with diamond powders of various particle sizes and the created surfaces were monitored with an e.s.r. spectrometer. The results show a peak in the curve of the relative signal height versus abrasive particle size, occurring in the 4-8 μm region. Talysurf and optical microscope readings indicate that the amount of visible surface area formed increases with the particle size. A mechanism for the occurrence of the peak is discussed in terms of the total surface area that results from the sum of the contributions from visible surface area, fissures and microcracks, and embedded silicon particles.