Men's Black Onyx Gold Ring This bold, very masculine men's black onyx and diamond ring is sure to impress. A 10 X 8mm genuine black onyx gem stone, accented brilliantly by two white round diamonds, is set in 10K solid yellow gold on a wide band. The black onyx gemstone weighs roughly 2.1 carats. An outstanding contemporary men's black onyx ring with prominent character! This ring qualifies for free custom ring sizing. Size 10 is standard. When you order a custom size, please allow an additional 7-10 business days processing time.