The study of grown Sc 2 SiO 5 :Gd and Sc 2 SiO 5 :Fe crystals was carried out by the paramagnetic resonance method. It has been established that Fe 3+ ions replace Sc 3+ in both crystallographic positions, while Gd 3+ ions exhibit a single center localized in a larger position with a coordination number of 7. Measurement of the orientational behavior of the positions of transitions of Fe 3+ and Gd 3+ centers in two orthogonal planes made it possible to determine the parameters of their triclinic spin Hamiltonians. To determine the localization of impurity ions Cr 3+ , Fe 3+ , and Gd 3+ in scandium and yttrium silicates, the orientation of the main Z axes of the fine structure tensors of the second rank was used.