Accessory zircon from metasomatically altered granites of the Salmi intrusion has been studied by means of optic and SEM microscopy, accompanied with electron-probe analysis of trace elements. Peculiarities of morphology, inner structure and composition of the zircons were revealed. The correlation of those to the rock alteration degree has been established. Statistical pattern of compositional variations of zircons are estimated. The results are presented in the paper.