London Blue Topaz and Diamond Halo Ring Blue Topaz 3.8 ct. Diamond 0.43 ct. 18K White Gold Other Products. Black Diamond Rings 18K White Gold More Detail Black Diamond Studs Earrings 18K Black Gold More Detail Diamond Halo Ring 18K White Gold More Detail Three Color Gemstones Ring in 9K Yellow Gold Three Color Gemstones Ring in 9K Yellow Gold More Detail