Optical and structural properties of single crystalline alpha-Al(2)O(3) were changed by the implantation of high fluences of Ni ions. Sapphire single crystals with < 0001 > orientation were implanted at room temperature with 150 keV nickel ions, Implantation fluences were in the range 0.3x10(15) to 1.8x10(17) cm(-2). After implantation the optical absorption spectra reveal the presence of a band peaking in the region 300 - 500 nm, depending on the retained fluence. This is usually related to the presence of metallic particles. X-ray diffraction (XRD) studies show the presence of metallic Ni after implantation. Annealing in oxidizing atmosphere promotes the recrystallization of the host matrix along with the formation of NiAl(2)O(4) as deduced from Rutherford Backscattering Spectrometry (RBS) and confirmed through XRD. In vacuum the particles formed are metallic like with some Ni spinel also present. The control of the implantation fluence, temperature and annealing atmosphere allows tailoring the component phases.