Optical glass, and precision press-molding preform for optical element

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PROBLEM TO BE SOLVED : To provide an optical glass having predetermined optical constants by a composition containing no GeO2and Ta2O5at all, which are expensive, and containing a certain amount or more amount of rare earth oxides; and to provide a preform for precision press molding, and an optical element. SOLUTION : The optical glass includes a composition of, in mass%, 0.5-9.0% SiO2, 10.0-22.0% B2O3, 30.0-50.0% La2O3, 14.0-30.0% Gd2O3, 0.5-10.0% ZrO2, 9.0-18.0% TiO2and 1.0-13.5% Nb2O5, which is constituted so as to satisfy 50.5%≤(La2O3+Gd2O3)≤64.0%. COPYRIGHT : (C)2011, JPO&INPIT