187Re

187Re, or rhenium-187, is a naturally occurring radioisotope of the transition metal rhenium (Re, atomic number 75). In nature, rhenium consists mainly of two isotopes, 185Re and 187Re, with 187Re accounting for about 62–63 percent of natural rhenium. 187Re is long-lived and decays by beta minus emission to 187Os (osmium-187). Its half-life is about 41.2 billion years, among the longest known for any radionuclide.

The 187Re–187Os decay system is used for geochronology. The ratio of 187Re to 187Os in sulfide minerals and other rocks evolves over time, enabling age determinations by isochron methods. This dating is valuable for constraining the timing of ore formation, crustal and mantle processes, and meteorite and planetary histories.

Occurrence and production: Re occurs mainly in molybdenite and is refined as a by-product of molybdenum and copper mining. Natural rhenium is dominated by 187Re, so the isotope composition of naturally occurring rhenium supports Re–Os dating without extensive enrichment. Enriched materials for research and certain industrial applications can be prepared to adjust isotopic composition as needed.

Safety and handling: As a long-lived radionuclide, 187Re is managed with standard radiological precautions in controlled facilities. It has no known biological role and is not used in medical imaging. Its radiological relevance is primarily within geological dating and industrial isotope studies.