PURPOSE: To provide a heat absorbing hard glass containing specific amounts of SiO2, Al2O3, B2O3, alkaline earth metal oxides, ZnO, Fe2O, etc. and having specific transition point and heat expansion coefficient and excellent heat resistance.

CONSTITUTION: At least 98wt% of the titled compositon is composed of 48W 62wt% of SiO2, 10W20% of Al2O3, 0W7% of B2O3 (SiO2+Al2O3 is ≥65%), 18W30% of alkaline earth metal oxides (BaO is 10W23%, SrO+CaO+MgO is 5W10%), 2W10% of ZnO, and 0.3W1.5% of FeO+Fe2O3 reduced to Fe2O. The glass composition has a transition point of ≥700°C and a heat expansion coefficient of ≤55×10-7/°C between 0 and 300°C. The hard glass thus obtained is resistant to deformation even at high temperature caused by the absorption of infrared ray, and accordingly, has excellent heat resistance.