The liquidus surface structure and field of LiB3O5 (LBO) primary crystallization have been revealed in Li2O-B2O3-MoO3 ternary system. The optimization of charge composition and growth conditions results in large volume optical quality LBO single crystals yielding. Crystallographic properties and real defect structure of grown LBO single crystals have been investigated by X-ray powder diffraction method and X-ray reflection topography. The volume of the crystals is partly free of any structural imperfections.