Optical Glass

An optical glass with RI at least 1.70 and Abbe value at least 48 of composition: SiO2 0.5-10, B2O3 15-35, La2O3 35-51, ZnO 0.5-10, ZrO2 2-8, F- 0.5-5, M2O 0-2.5, AO 0-4.5, where M2O is selected from Li, Na or K, AO from Mg, CA, Sr and Ba, and SiO2+B2O3=20-43 (all wt%).