10K Yellow Gold Vintage Blue Topaz & Diamond Ring Size 6 3/4. This is a beautiful vintage ring set in 10K yellow gold that features a 10x8 mm oval blue topaz. It is approximately 3.4 carats. There are 2 small accent diamonds that are approximately 0.02 ctw. Beautiful swirled design and is a size 6 3/4. There is a slight bend in the bottom of the band which jewelers should be able to repair (see photos). Otherwise in good condition. This piece weighs 4.39 grams.