Natural diamond irradiated by krypton ions with 210 or 247MeV energy within a dose range of 5x10 1 0 -1.2x10 1 4 cm - 2 has been investigated by optical absorption, photoluminescence and electric methods. The main features of the absorption spectra of the irradiated diamond are a GR1-band and a continuous absorption band in the ultraviolet part of a spectrum. 800 o C annealing causes the GR1 band disappearance, but the continuous absorption band in the ultraviolet part of the spectrum decreases up to 1400 o C. The changes at the dose of 10 1 3 cm - 2 in absorption intensity of these bands can be attributed to overlapping of ion tracks. The tracks of ions give rise to deep trap levels in the forbidden gap of diamond, which are impossible to anneal even at 1450 o C.