The microcrack accumulation in impact damaged -quartz plates prior to and after the Ar+-ion implantation was studied with the acoustical emission (AE) method. The 40 keV implantation doses of 1014 and 1016 ion/cm2 were applied. The statistical analysis of the energy distribution in impact-induced AE time series detected in unirradiated samples showed a random (poissonian type) accumulation of defects which is specific for mechanical destruction of homogeneous brittle materials. The energy distribution in the AE time series excited when damaging the preliminary implanted samples followed a power law typical for the fracture of heterogeneous solids such as rocks, ceramics, etc. The optical photography evidenced a transition from brittle (prior to implantation) to ductile damage formation caused by the disturbed interconnectivity of the crystalline structure in irradiated specimens.