Zn nanoparticles were grown at the surface of ZnO single crystal by UV laser radiation. As a result “black” ZnO was formed. The formation of Zn nanoparticles by the laser is explained by Thermogradient effect. According to the effect, the gradient of temperature induced by nanosecond laser radiation leads to generation of Zn interstitial atoms and to their concentration at the irradiated surface of the ZnO crystal. This was proved by huge increase of electrical conductivity up to 250 times with the increase of laser radiation intensity. Moreover, the topography change of the irradiated surface was not observed till laser intensity Imax = 290 MW/cm2. The increase of Zni atoms concentration at the irradiated surface of the sample at certain concentration leads to conglomeration of Zni atoms forming Zn nanoparticles with size up to 50nm.