Iridium

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Iridium is a chemical element; it has the symbol Ir and atomic number 77. This very hard, brittle, silvery-white transition metal of the platinum group is considered the second-densest naturally occurring metal (after osmium), with a density of 22.56 g/cm3 (0.815 lb/cu in) as defined by experimental X-ray crystallography. 191Ir and 193Ir are the only two naturally occurring isotopes of iridium, as well as the only stable isotopes; the latter is the more abundant. It is one of the most corrosion-resistant metals, even at temperatures as high as 2,000 °C (3,600 °F). Iridium was discovered in 1803 in the acid-insoluble residues of platinum ores by the British chemist Smithson Tennant. The name iridium, derived from the Greek word iris (rainbow), refers to the various colors of its compounds. Iridium is one of the rarest elements in Earth's crust, with an estimated annual production of only 6,800 kilograms (15,000 lb) in 2023. The dominant uses of iridium and its alloys are in high-performance...

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