Stylishly stunning. Studio Silver's ring is set in 18k gold over sterling silver with a labradorite stone (8-1/4 ct. t.w.) adding an elegant touch. Approximate stone size: 3/4 inch x 5/8 inch. Size 7 and 8. Almost all gemstones and blue and black diamonds have been treated to enhance their beauty and require special care. All gemstone carat weights (ct. t.w.), if mentioned, are approximate; variance may be .05 carat. Ring Sizer.