PURPOSE: To obtain a glass having a heat-expansion curve free from large kinking by melting a glass prepared by adding a specific amount of a fluoride to a specifically composed SiO2-Al2O3-ZnO-MgO-PbO-TiO2, forming the resultant glass composition, heating the formed product and crystallizing it with heat.

CONSTITUTION: A glass starting material is prepared by using 30W65wt.% of SiO2, 5W25wt.% of Al2O3, 10.5W40wt.% of ZnO, 3.5W20wt.% of MgO, 0.5W10wt.% of PbO, 0W15wt.% of CaO+SrO+BaO, 2W15wt.% of TiO2, 0W10wt.% of B2O3, 0W10wt.% of La2O+Y2O3+Gd2O3+Ta2O5+Nb2O5+WO3, 0W5wt.% of ZrO2+P2O5+SnO2, with proviso that ZrO2 is 0W2.5wt.%, P2O5 0W5wt.%. SnO2 is 0W2wt.% As2O3+Sb2O3 is 0W2wt.% and adding fluorides of the metals in the metal oxides used in such an amount as the total amount is 0W5wt.%, calculated as F element. The starting material is melted, formed, then heated at elevated temperature and crystallized at a temperature lower than 1,150°C. Thus, a crystalline glass which is suitable for a magnetic head base is obtained, because it has a wide range of heat expansion coefficient, high dense texture and uniformity.