The optical properties of trivalent chromium ions in La3Ga5SiO&4 crystals have been investigated by means of absorption, emission, excitation, and lifetime measurements. The particular intermediate value of the octahedral crystal field Dq/B 2.5 causes the overlapping of the Tz with the E and T~levels. This overlap is the origin of Fano resonances in the absorption spectrum and of the simultaneous presence of broadband and narrow-line emissions. Polarized measurements have allowed the determinations of second-order efFects such as the tetragonal or orthorhombic distortion of the octahedron of oxygen ions around the chromium ion. Moreover the temperature shift of the peak and the nonexponential decay of the broad emission band are indications of the disorder present in the crystal lattice. All these results produce a fairly complete picture of the energy levels of Cr + ions in a typical crystal of the Ca-gallogermanate family.ments and lasing performances on this system were already published. "' In this paper we present a new and more detailed study on the optical properties of Cr + ion in the La3Ga5SiOq4 crystal. In particular we have performed absorption, emission, excitation and lifetime measurements from which we derive a complete description of the Cr + energy levels.