Optical glass, a preform for press molding and optical element

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Provided is an optical glass that shows good transmissivity across the entire visible spectrum and which has excellent glass stability, a high refractive index, and low dispersion. Shown in mol% on an oxide basis, this optical glass contains B2O3 : 45-80%, La2O3 : 5-32%, Gd2O3 : 0-25%, Y2O3 : 0-20%, Yb2O3 : 0-0.15%. The ratios of the amounts of rare earth components La2O3, Gd2O3 and Y2O3 to the total amount of rare earth components (Ln2O3) fulfill 0.50 ≦ La2O3/Ln2O3 ≦ 0.77 and 0.12 ≦ Y2O3/Ln2O3 ≦ 0.345 if 0 ≦ Gd2O3/Ln2O3 < 0.21 and fulfill 0.40 ≦ La2O3/Ln2O3 ≦ 0.74 and 0 ≦ Y2O3/Ln2O3 ≦ 0.25 if Gd2O3/Ln2O3 ≧ 0.21. The refractive index nd is 1.736-1.765, the Abbe number νd is 56 or less, and the relational expression νd ≧ (-45.131×nd + 132.001) is fulfilled.