atomic number 77, a hard, dense silvery-white metal.


Iridium, A very hard, brittle, silvery-white transition metal of the platinum group, was discovered in 1803 among insoluble impurities in natural platinum. Smithson Tennant the primary discoverer, named iridium for the Greek goddess Iris, personification of the rainbow, because of the striking and diverse colors of its salts. Iridium is one of the rarest elements in Earth's crust, with annual production and consumption of only three tonnes.


Iridium is the most corrosion-resistant material known. It is used in special alloys and forms an alloy with osmium, which is used for pen tips and compass bearings. Due to its resistance to corrosion, iridium was used in making the standard meter bar of Paris. The bar was made of 90 percent platinum and 10 percent iridium. However, it was replaced as a unit of measure in the 1960s when the meter was redefined by the orange-red spectral line of krypton-86. It is also used for the contacts in spark plugs because of its high melting point and low reactivity.


Iridium is widely used to harden platinum, make devices requiring high temperatures, and in electrical contacts. It’s also used incoating optical lenses to reduce glare and enhance clarity. Osmiridium, a combination of the elements osmium and iridium, is used for fountain pens and compass bearings.

sources of iridium

Native platinum has many of the platinum group of metals, including iridium. Iridium is commercially recovered as a by product in nickel mining. The element is named iridium for its colored salts.