The scale-like glass (10) with improved heat resistance and chemical durability is formed from a glass base material containing virtually no alkali metal oxide and wherein 55 = SiO2 = 65, 8 = Al2O3 = 15, 47 = (SiO2-Al2O3) = 57, 1 = MgO = 5, and 20 = CaO = 30, represented in mass%. It is preferred that the glass base material also contain 0.1 to 5 mass% of TiO2. The temperature difference ?T, calculated by subtracting the devitrification temperature from the working temperature of the glass base material, is preferably in the range of 0 to 80°C. ?W2, the index of the alkali resistance of the glass base material, is preferably in the range of 0.1 to 3 mass%.
