Despite high pressure grinding rolls (HPGR) have been widely used in mining industry during the past decades, there are limited systematic quantifications on the properties of the particles after comminution. Furthermore, the influence of micro-cracks on gold ore leaching has not been further investigated. Gold ore samples were subjected to two different open-circuit comminutions: conventional jaw crusher and HPGR. Particle size distribution was measured and the fractal dimension based on fractal theory was obtained. Combined with scanning electron microscopy (SEM) and stereomicroscopy, particle spherical indices and micro crack properties were further explored. The results show that HPGR produced higher proportion of fines and less uniformity in comparison with the jaw crusher, reflected by the larger fractal dimension. There was a marked increase in spherical indices from HPGR in 9.5-4.0 nun size fraction. Through the quasi-hydrostatic pressure, more micro-cracks were generated in the HPGR products, resulting in enhanced infiltration of leaching reagent and gold recovery in full-slime and heap cyanide leaching. This paper highlights the importance of the effective micro-crack formation and proposes a leaching kinetic model for further prediction of leaching cycle.