It's a blue topaz that reflects a pool blue, as it has probably lost some color saturation over the years. Alas, this is true of irradiated material. If I were in your position I'd ask myself how often I'd wear it. Looking only at the value of materials, I think it's worth $500, $600 tops considering the cost of the setting. But obviously if you think you'll be wearing it a lot it'll have more worth to you than someone like me who doesn't wear honkers often.
