Provided is optical glass containing, in terms of mol % of cations: 10 to 60% of a La.sup.3+ component; more than 0% and up to 75% of a Ga.sup.3+ component; and 5 to 75% of a Nb.sup.5+ component, in which a total amount of the La.sup.3+ component, Ga.sup.3+ component, and Nb.sup.5+ component is 60 to 100%.

A holding member is used in a glass manufacturing apparatus that cools down a glass raw material that has been levitated by gas and has been heated and melted, and manufactures glass. The holding member includes a gas injection surface that includes a plurality of injection ports from which the gas is injected. The gas injection surface includes a first region and a second region, the first region including first injection ports that are some injection ports of the plurality of injection ports, the second region including second injection ports that are different from the first injection ports from among the plurality of injection ports. The first region is located inside the second region, when the gas injection surface is viewed from the top. An area of the injection ports per unit area of the first region is smaller than the area of the injection ports per the unit area of the second region. The area of the injection ports per the unit area of the first region is a ratio of the total of cross-sectional areas of the first injection ports to the area of the first region when the gas injection surface is viewed from the top. The area of the injection ports per the unit area of the second region is the ratio of the total of cross-sectional areas of the second injection ports to the area of the second region when the gas injection surface is viewed from the top.

A holding member is used in a glass manufacturing apparatus that cools down a glass raw material that has been levitated by gas and has been heated and melted, and manufactures glass. The holding member includes a gas injection surface that includes a plurality of injection ports from which the gas is injected. The gas injection surface includes a first region and a second region, the first region including first injection ports that are some injection ports of the plurality of injection ports, the second region including second injection ports that are different from the first injection ports from among the plurality of injection ports. The first region is located inside the second region, when the gas injection surface is viewed from the top. An area of the injection ports per unit area of the first region is smaller than the area of the injection ports per the unit area of the second region. The area of the injection ports per the unit area of the first region is a ratio of the total of cross-sectional areas of the first injection ports to the area of the first region when the gas injection surface is viewed from the top. The area of the injection ports per the unit area of the second region is the ratio of the total of cross-sectional areas of the second injection ports to the area of the second region when the gas injection surface is viewed from the top.

A mold includes a lower mold core and an upper mold core. The lower mold core has a first outside surface and a first molding surface including a first molding portion and a first supporting portion surrounding the molding portion. The upper mold core has a second molding surface opposite to the first molding surface and encloses a molding cavity with the first molding surface. The lower mold core includes a first gas inlet on the first outside surface, a first gas outlet on the first supporting portion, and a first gas channel in the lower mold core, the first gas channel connecting the first gas inlet and the first gas outlet. Gas flow out from the first gas outlet to separate the glass product from the lower mold core before the glass product is completely cooled down, which can avoid many adverse effects during the glass product process.

An optical glass includes, in terms of mol % of cations, a total amount of La.sup.3+, Y.sup.3+, and Gd.sup.3+ components falling within a range of from 5% to 65% and a total amount of Zr.sup.4+, Hf.sup.4+, and Ta.sup.5+ components falling within a range of from 5% to 65%, and a relationship expressed in Expression (1) given below is satisfied. (La.sup.3++Y.sup.3++Gd.sup.3+)×(Zr.sup.4++Hf.sup.4++Ta.sup.5+)≥400 (%).sup.2

A production apparatus that continuously produces plate glass, includes a molding member configured to mold molten glass to form a glass ribbon, wherein the molding member is (i) constituted with graphite or includes a portion constituted with graphite, and/or (ii) supported by a support member containing graphite, wherein in a case of (i), the molding member is surrounded by a fence, and in a case of (ii), the support member is surrounded by the fence together with the molding member, and wherein a space surrounded by the fence is adjusted to have an oxygen concentration of less than or equal to 100 ppm.

A production apparatus that continuously produces plate glass, includes a molding member configured to mold molten glass to form a glass ribbon, wherein the molding member is (i) constituted with graphite or includes a portion constituted with graphite, and/or (ii) supported by a support member containing graphite, wherein in a case of (i), the molding member is surrounded by a fence, and in a case of (ii), the support member is surrounded by the fence together with the molding member, and wherein a space surrounded by the fence is adjusted to have an oxygen concentration of less than or equal to 100 ppm.

Provided is an optical glass containing glass-forming cations, the optical glass satisfying, expressed in cation percent, 10 cat %B.sup.3+50 cat %, 15 cat %La.sup.3+35 cat %, 20 cat %Nb.sup.5+50 cat %, and 15 cat %Ti.sup.4+25 cat %.

A mold includes a lower mold core and an upper mold core. The lower mold core has a first outside surface and a first molding surface including a first molding portion and a first supporting portion surrounding the molding portion. The upper mold core has a second molding surface opposite to the first molding surface and encloses a molding cavity with the first molding surface. The lower mold core includes a first gas inlet on the first outside surface, a first gas outlet on the first supporting portion, and a first gas channel in the lower mold core, the first gas channel connecting the first gas inlet and the first gas outlet. Gas flow out from the first gas outlet to separate the glass product from the lower mold core before the glass product is completely cooled down, which can avoid many adverse effects during the glass product process.

Provided is a method that can manufacture a glass material having excellent homogeneity by containerless levitation. With a block (12) of glass raw material held levitated above a forming surface (10a) of a forming die (10) by jetting gas through a gas jet hole (10b) opening on the forming surface (10a), the block (12) of glass raw material is heated and melted by irradiation with laser beam, thus obtaining a molten glass, and the molten glass is then cooled to obtain a glass material. Control gas is jetted to the block (12) of glass raw material along a direction different from a direction of jetting of the levitation gas for use in levitating the block (12) of glass raw material or the molten glass.