A borate glass includes from 25.0 mol % to 70.0 mol % B2O3; from 0.0 mol % to 10.0 mol % SiO2; from 0.0 mol % to 15.0 mol % Al2O3; from 3.0 mol % to 15.0 mol % Nb2O5; from 0.0 mol % to 12.0 mol % alkali metal oxides; from 0.0 mol % to 5.0 mol % ZnO; from 0.0 mol % to 8.0 mol % ZrO2; from 0.0 mol % to 15.0 mol % TiO2; less than 0.5 mol % Bi2O3; and less than 0.5 mol % P2O5. The optical borate glass includes a sum of B2O3+Al2O3+SiO2 from 35.0 mol % to 76.0 mol %, a sum of CaO+MgO from 0.0 mol % to 35.5 mol %. The borate glass has a refractive index, measured at 587.6 nm, of greater than 1.70, a density of less than 4.50 g/cm3, and an Abbe number, VD, from 20.0 to 47.0.