An iridium ring is a piece of jewelry that is made out of the precious metal iridium and worn around the finger. Iridium is one of the platinum metals. It's rare and expensive because it's the most corrosion-resistant metal on the planet and is far harder to melt than gold.
American Elements was the first company to successfully produce a line of pure iridium jewelry, including wedding bands, bracelets, earrings and necklaces. The production required high-grade technology because of iridium's extremely high melting point. Iridium is the lowest tarnishing element in the known universe, and it is said to give off a remarkable luster when refined into jewelry.