<p>Disclosed is a glass composition for lamps mainly containing SiO2 (silicon dioxide) and further containing 12-17 wt% of Na2O (sodium oxide), 2.5-4 wt% of MgO (magnesium oxide) and 5.3-7.3 wt% of CaO (calcium oxide) with MgO and CaO being 8-11 wt% in total. With this constitution, the glass composition can be obtained at low cost while having excellent strength and workability. Furthermore, this glass composition does not erode a melting furnace and only a small amount of alkali is dissolved therefrom.</p>
