Iridium

Iridium is a chemical element with the symbol Ir and atomic number 77. It is a hard, dense, brittle transition metal in the platinum group, notable for its exceptional corrosion resistance and very high melting point.

Its melting point is about 2,446°C and its density around 22.56 g/cm³, making it one of the densest elements. Iridium forms durable alloys with platinum to improve hardness and high-temperature stability, and is used in specialized applications where mechanical wear and heat resistance are essential.

Iridium is rare in the Earth's crust and occurs with other platinum-group metals. It is typically obtained as a byproduct of nickel and copper mining. Significant sources include the Bushveld Complex in South Africa, as well as deposits in Russia and Canada.

Natural iridium consists mainly of two stable isotopes, 191Ir and 193Ir. The radioactive isotope 192Ir is produced for medical radiotherapy and industrial radiography, where it serves as a gamma source.

Common applications include high-temperature crucibles and equipment for growing single crystals; electrical contacts and spark plugs; and catalysts for certain chemical reactions. It is also alloyed with platinum to increase hardness and wear resistance in jewelry and other specialized parts.

Iridium was discovered in 1803 by Smithson Tennant in London, who isolated it from dissolving platinum ores. The name derives from iris, Latin for rainbow, in reference to the colorful salts of iridium.