Two high content terbium apatites, Tb₅Si₂BO₁₃ and Tb_4.66Si₃O₁₃, have been successfully synthesized by sol–gel method and have been crystallized from high temperature flux. Their structures were identified by single crystal X-ray diffraction and were found to belong to the hexagonal system with space group P6₃/m and unit cell parameters of a = 9.2569(10) Å, c = 6.8297(12) Å and Z = 2 for Tb₅Si₂BO₁₃ and a = 9.493(4) Å,c = 6.852(5) Å and Z = 2 for Tb_4.66Si₃O₁₃, respectively. The diffuse optical reflection spectra clearly indicate that the two crystals have good optical transparency in the range of 500–1500 nm. The paramagnetic behaviours of Tb₅Si₂BO₁₃ and Tb_4.66Si₃O₁₃ from 2 K to 300 K are confirmed by magnetic susceptibility measurements. In comparison with other known Tb containing magneto-optical (MO) glass and crystals, Tb₅Si₂BO₁₃ and Tb_4.66Si₃O₁₃ are found to be promising magneto-optical materials in the visible–near IR range due to the high Tb³⁺ concentrations in both compounds.