Two Fe3+ centers, as well as the spectrum of an uncontrolled Cu2+ impurity, were studied using paramagnetic resonance in a specially grown Y2SiO5:Fe crystal. The parameters of spin Hamiltonians are determined both in laboratory and local (with diagonal second-rank fine structure tensor or hyperfine interaction tensor A) coordinate systems. The localization of Fe3+, Cr3+, Gd3+ and Cu2+ centers in yttrium and scandium silicates is discussed.