Rhenium was discovered in 1925 by the German chemists Walter Noddack, Ida Tacke and Otto Berg, who detected it in platinum ore and columbite. They named it after the river Rhine, from the Latin Rhenus. It was the last element with a stable isotope to be discovered in nature. Rhenium is a dense, silvery-white metal with one of the highest melting points of all, used in high-temperature superalloys for jet-engine turbine blades and in catalysts. One of the rarest and most costly of metals, rhenium is prized for the nickel-based superalloys of jet-engine and rocket parts, where its very high melting point resists extreme heat, and it serves as a catalyst in producing high-octane petrol.
Rhenium is never mined in its own right, recovered only as a trace byproduct of processing molybdenum and copper ores, and it ranks among the very scarcest elements in the Earth's crust, a scarcity that keeps its price among the highest of the industrial metals. The decay of rhenium-187 into osmium-187, occurring at an extremely slow, well-characterised rate, gives geochemists the rhenium-osmium dating method, used to date molybdenite ore deposits and some of the oldest meteorites in the solar system. The fumaroles of Kudryavy, a volcano on the Kuril island of Iturup, were found in the 1990s to deposit rheniite, a rare rhenium sulfide mineral and the only place on Earth where rhenium is known to concentrate naturally into a mineral of its own rather than merely occurring as a trace in other ores.