Ni + has been implanted in amorphous silica layers and silica glasses at two dose levels (10 16 and 10 17 Ni + cm −2 ) and two different energies (30 and 160 keV). Superparamagnetic and ferromagnetic behaviors were observed with a SQUID magnetometer at RT and 5 K, respectively. Using Langevin’s theory, the size of the metallic nanoparticles were deduced to ranges between 2 and 6.5 nm in good agreement of HRTEM observations. The E′ type center and the neutral oxygen vacancy (NOV) defects were observed by UV–Vis absorption. Finally, in samples annealed at 600°C under Ar or Ar+H 2 atmospheres two different phenomena were observed: the reduction of Ni 2+ to Ni 0 and the elimination of defects introduced by implantation.