A glass composition SiO2, Al2O3, B2O3, and RO, where RO represents one kind or two or more kinds selected from MgO, CaO, SrO, and BaO, and allows two or more kinds of crystals selected from a SiO2—Al2O3—RO-based crystal, a SiO2-based crystal, and a SiO2—Al2O3-based crystal to precipitate in a temperature range of from a liquidus line temperature to (the liquidus line temperature—50° C.)