Glass has a refractive index of 1.55 or more, and has, in an x-ray absorption fine structure (XAFS) analysis of platinum, a peak intensity ratio expressed by A.sub.max/A.sub.ave of 1.13 or more, where A.sub.max denotes a maximum value of a white line within an energy range of 13,270 eV to 13,290 eV, and A.sub.ave denotes an average absorption in an energy range of 13,290 eV to 13,390 eV.

To provide an optical glass having a high refractive index and a relatively low specific gravity, and an optical element.

An optical glass which is a SiO.sub.2—TiO.sub.2—Nb.sub.2O.sub.5-based glass, and in which the content of SiO.sub.2 is 10% by mass or greater, the total content of Na.sub.2O, K.sub.2O, and Cs.sub.2O(Na.sub.2O+K.sub.2O+Cs.sub.2O) is 11.0% by mass or less, and the specific gravity and the refractive index nd thereof satisfy formula (1).

nd≥0.2×specific gravity+1.18  (1):

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 failing 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.3+)≥400(%).sup.2.

This technology is directed to the preparation of doped-bismuth-silicate seed crystals through controlled crystallization (e.g. dimensionality of growth and nucleation mechanism) and the method of forming high purity single seed (particle size ranges from micrometers to millimeters) for various uses. These seed crystals have a nominal stoichiometry of Bi.sub.2-xA.sub.xSiO.sub.5, Bi.sub.2-xA.sub.xSi.sub.3O.sub.9, Bi.sub.4-xA.sub.xSi.sub.3O.sub.9, and Bi.sub.12-xA.sub.xSiO.sub.20, where A is a rare earth dopant selected from La, Ce, Nd, Pr, and/or Sm.

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

Glasses containing silicon dioxide (SiO.sub.2) and/or boron oxide (B.sub.2O.sub.3) as glass formers and having a refractive index n.sub.d of greater than or equal to 1.80, as measured at 587.56 nm, a density of less than or equal to 5.5 g/cm.sup.3, as measured at 25° C., and a high transmittance to, particularly to blue light, are provided. Optionally, the glasses may be characterized by a high transmittance in the visible and near-ultraviolet (near-UV) range of the electromagnetic spectrum and/or good glass forming ability.

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 failing 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.3+) 400(%).sup.2

An optical glass comprising: by cation %, more than 0% and up to 40% of a content rate of La.sup.3+; 15% to 65% of a content rate of Ti.sup.4+; and more than 0% and up to 20% of a content rate of Zr.sup.4+; wherein a refractive index (n.sub.d) with respect to a d-line is from 2.00 to 2.35.

This technology is directed to the preparation of doped-bismuth-silicate seed crystals through controlled crystallization (e.g. dimensionality of growth and nucleation mechanism) and the method of forming high purity single seed (particle size ranges from micrometers to millimeters) for various uses. These seed crystals have a nominal stoichiometry of Bi.sub.2-xA.sub.xSiO.sub.5, Bi.sub.2-xA.sub.xSi.sub.3O.sub.9, Bi.sub.4-xA.sub.xSi.sub.3O.sub.9, and Bi.sub.12-xA.sub.xSiO.sub.20, where A is a rare earth dopant selected from La, Ce, Nd, Pr, and/or Sm.

Ion sustained-release composite particles include ion sustained-release glass and a polymer compound, wherein the polymer compound includes a homo polymer or a copolymer of a (meth)acrylate compound having a hydroxyl group.