OPTICAL AND OPHTHALMIC GLASS WITH REFRACTIVE INDICES ND >1.58, ABBE NUMBERS >45 AND DENSITIES <2.75 G/CM3

A borosilicate glass composition suitable for use as an eyeglass lens, characterized by having a refractive index nd.gtoreq.1.58, an Abbe number vd.gtoreq.45, a density .rho..ltoreq.2.75 g/cm.sup.3, and an excellent aptitude for chemical hardening, consisting essentially of the following composition, in weight percent: ______________________________________ SiO.sub.2 51-65 B.sub.2 O.sub.3 2-14 Al.sub.2 O.sub.3 0-5 SiO.sub.2 + B.sub.2 O.sub.3 + Al.sub.2 O.sub.3 62-73 Li.sub.2 O 4-13 Na.sub.2 O 0-4 K.sub.2 O 0-4 Li.sub.2 O + Na.sub.2 O + K.sub.2 O 7-15 CaO 1-19 MgO 0-11 CaO + MgO 6-22 TiO.sub.2 0-8 ZrO.sub.2 0-9. ______________________________________