Sapphire and Diamond Half Eternity Ring Mark Parkhouse Antiques Sapphire and Diamond Eternity Platinum Ring For Sale at 1stDibs A Sapphire and Diamond eternity ring At Auction: A SAPPHIRE AND DIAMOND ETERNITY RING: eight each sapphires Sapphire and Diamond Eternity Platinum Ring For Sale at 1stDibs. An 18 carat gold half hoop eternity ring, set with three round mid blue sapphires (each approximately 3mm in diameter) of mid to dark blue colour. Each sapphire is alternated with a brilliant cut white diamond (two in total), each approximately 3mm (0. 10 carats), of IJ colour and SI clarity. The stones are set across the front of the band, spreading approximately 16mm along the finger. The ring measures 3. 4mm in width and weighs 3. 5 grams. UK hallmarks (no date letter; likely circa 19902000). Ring size: M (can be resized free of charge).