Abstract: This invention is directed to photochromic glasses which darken to a brown coloration upon exposure to actinic radiation, which glasses have a refractive index of about 1.6, an Abbe number between 42-47, a density less than 2.82 g/cm.sup.3, and are preferably essentially free of TiO.sub.2. The glass compositions consist generally, in weight percent, of:______________________________________ SiO.sub.2 43-52 K.sub.2 O 2-9 Nb.sub.2 O.sub.5 6-16 B.sub.2 O.sub.3 12.5-18 MgO 0-5 Ag 0.100-0.175 Al.sub.2 O.sub.3 0-3 CaO 0-5 Cl 0.140-0.350 ZrO.sub.2 6-14 SrO 0-9 Br 0.093-0.195 Li.sub.2 O 1.5-3.5 BaO 0-9 CuO 0.008-0.030. Na.sub.