β-BaB[2]O[4] (BBO) has been considered to be an excellent non-linear optical material in single crystal form; however, BaO-B[2]O[3] can also form a glass. BaO-B[2]O[3] glass has a density of about 3.9 g/cm[3], a glass transition around 525[o]C, an onset of crystallization around 560[o]C, a maximum crystallization at 585[o]C and a refractive index of 1.59. Optically transparent BaO-B[2]O[3] glass-ceramics have been successfully prepared by controlled crystallization