High Quality Content by WIKIPEDIA articles! There are two natural isotopes of iridium (Ir), and 34 radioisotopes, the most stable radioisotope being 192Ir with a half-life of 73.83 days, and many nuclear isomers, the most stable of which is 192m2Ir with a half-life of 241 years, all other isomers have half-lives under a year, most under a day.