The present invention provides an optical glass that has a high refractive index property and excels in a light transmittance property in the visible range and in resistance to devitrification. The optical glass contains from 3 to 18 mass % of SiO.sub.2, from 5 to 11.5 mass % of B.sub.2O.sub.3, from 0 to 7 mass % of Al.sub.2O.sub.3, from 0 to 11 mass % of CaO, 1 mass % or less of ZnO, from 7 to 20 mass % of TiO.sub.2, from 3 to 38 mass % of Nb.sub.2O.sub.5, from 27 to 49.8 mass % of La.sub.2O.sub.3, from 6 to 14 mass % of Gd.sub.2O.sub.3, from 0 to 5 mass % of Y.sub.2O.sub.3, less than 6 mass % of Ta.sub.2O.sub.5, and 0.6 mass % or less of WO.sub.3, with a ratio of B.sub.2O.sub.3/SiO.sub.2 being from 1 to 2.

The present invention provides an optical glass that has a high refractive index property and excels in a light transmittance property in the visible range and in resistance to devitrification. The optical glass contains from 3 to 18 mass % of SiO.sub.2, from 5 to 11.5 mass % of B.sub.2O.sub.3, from 0 to 7 mass % of Al.sub.2O.sub.3, from 0 to 11 mass % of CaO, 1 mass % or less of ZnO, from 7 to 20 mass % of TiO.sub.2, from 3 to 38 mass % of Nb.sub.2O.sub.5, from 27 to 49.8 mass % of La.sub.2O.sub.3, from 6 to 14 mass % of Gd.sub.2O.sub.3, from 0 to 5 mass % of Y.sub.2O.sub.3, less than 6 mass % of Ta.sub.2O.sub.5, and 0.6 mass % or less of WO.sub.3, with a ratio of B.sub.2O.sub.3/SiO.sub.2 being from 1 to 2.

A fiber optic plate 122 including a plurality of core glasses 122a, a clad glass 122b covering the core glass 122a, and a light-absorbing glass 122c disposed between the plurality of core glasses 122a, wherein a content of TiO.sub.2 in the core glass 122a is 7% by mass or less, a content of B.sub.2O.sub.3 in the core glass 122a is 15% by mass or more, and a content of WO.sub.3 in the core glass 122a is more than 0% by mass.

A fiber optic plate 122 including a plurality of core glasses 122a, a clad glass 122b covering the core glass 122a, and a light-absorbing glass 122c disposed between the plurality of core glasses 122a, wherein a content of TiO.sub.2 in the core glass 122a is 7% by mass or less, a content of B.sub.2O.sub.3 in the core glass 122a is 15% by mass or more, and a content of WO.sub.3 in the core glass 122a is more than 0% by mass.

Provided is a glass material having a high light transmittance in a short wavelength range and easily producible. A glass material contains, in terms of % by mole, 5 to less than 30% Pr.sub.2O.sub.3 and 0.1 to 95% B.sub.2O.sub.3.

Provided is a glass material having a high light transmittance in a short wavelength range and easily producible. A glass material contains, in terms of % by mole, 5 to less than 30% Pr.sub.2O.sub.3 and 0.1 to 95% B.sub.2O.sub.3.

Provided is an optical glass that contains TiO.sub.2 and/or Nb.sub.2O.sub.5 as components of a glass composition, achieves a high light transmittance, and has excellent mass productivity. An optical glass contains TiO.sub.2 and Nb.sub.2O.sub.5 in a total amount of 20% by mole or more as components of a glass composition and has a basicity of 12 or more.

Provided is an optical glass that contains TiO.sub.2 and/or Nb.sub.2O.sub.5 as components of a glass composition, achieves a high light transmittance, and has excellent mass productivity. An optical glass contains TiO.sub.2 and Nb.sub.2O.sub.5 in a total amount of 20% by mole or more as components of a glass composition and has a basicity of 12 or more.

Glass compositions include boron oxide (B.sub.2O.sub.3), lanthanum oxide (La.sub.2O.sub.3), tungsten oxide (WO.sub.3) and zirconia (ZrO.sub.2) as components and may optionally include niobia (Nb.sub.2O.sub.5), titania (TiO.sub.2), bismuth oxide (Bi.sub.2O.sub.3), yttria (Y.sub.2O.sub.3), tellurium oxide (TeO.sub.2), SiO.sub.2, PbO and other components. The glasses may be characterized by high refractive index at 587.56 nm and low density at room temperature relative to known glasses.

Glass compositions include boron oxide (B.sub.2O.sub.3), lanthanum oxide (La.sub.2O.sub.3), tungsten oxide (WO.sub.3) and zirconia (ZrO.sub.2) as components and may optionally include niobia (Nb.sub.2O.sub.5), titania (TiO.sub.2), bismuth oxide (Bi.sub.2O.sub.3), yttria (Y.sub.2O.sub.3), tellurium oxide (TeO.sub.2), SiO.sub.2, PbO and other components. The glasses may be characterized by high refractive index at 587.56 nm and low density at room temperature relative to known glasses.