irídium

Iridium is a chemical element with the symbol Ir and atomic number 77. It is a member of the platinum group metals and is extremely rare in the Earth's crust. Iridium is a very dense, silvery-white, hard, brittle, and highly corrosion-resistant metal. It is one of the densest naturally occurring elements, with a density of 22.56 g/cm³. Its melting point is 2466 °C (4471 °F) and its boiling point is 4428 °C (8002 °F).

Iridium is found in very small amounts in meteorites, and in trace amounts in some ores. It is often found in association with platinum ores. The primary source of iridium is mining, although it is also recovered from spent nuclear fuel. Due to its rarity and high cost, iridium is not widely used in common applications. Its most significant use is in specialized industrial applications where its exceptional resistance to corrosion and high melting point are required.

These applications include the manufacture of spark plugs for high-performance engines, crucibles for high-temperature furnaces, and specialized electrodes for medical devices and scientific instruments. Iridium is also used in the production of certain catalysts and in some alloys to improve hardness and corrosion resistance. The discovery of iridium dates back to 1803, when it was identified by English chemist Smithson Tennant. The name "iridium" comes from the Greek word "iris," meaning rainbow, referring to the vibrant colors of its salts.