Black Onyx & Diamond Ring 10kt White Gold. ¬†A¬†lovely ornate vintage style black onyx and diamond ring in 10kt white gold. This beautiful ring is set with an oval buff top black onyx (2.88cts) with center opening. The center opening is topped by a millegrain edged diamond shaped setting with one single cut diamond (0.01ct). The ring is hallmarked 10k and is a size 5 1/2. The ring was cast, handset and is in very good condition. This includes an insurance appraisal of $550.00.