There are described blue luminescent glasses having the following compositions(a) 0 to 90 mole % alkali metal oxide (sodium oxide, potassium oxide, lithium oxide), individually or several together, 0 to 90 mole % alkaline earth metal oxide (magnesium oxide, calcium oxide, strontium oxide, barium oxide), individually or several together, with the proviso that the magnesium oxide and/or calcium oxide can only be present in an amount of up to 25 mole % and at least 2 mole % of alkali metal oxide and/or alkaline earth metal oxide must be present(b)7 to 95 mole % silica0 to 70 mole % boron oxide (B.sub.2 O.sub.3)0 to 85 mole % aluminum oxide(c) 0.01 to 40 mole % lead oxide (PbO).