77Ir Iridium

Year Discovered


Discovered By

Smithson Tennant of England

Biological Rating

Not necessary for life.


Named from the Greek word meaning “rainbow” (iridium compounds are quite colorful), iridium is a lustrous silvery-white metal, and is the most corrosion-resistant metal known, being completely unaffected by air, water or acids. It does react with molten salts and bases, and is used as a catalyst. Iridium is very hard and brittle and hardens other metals with which it is alloyed, especially platinum. These alloys are used in spark plugs, electrical contacts, and high temperature crucibles.

Biological Benefits

Iridium has no known biological use.

Role in Life Processes

No known benefits for life processes in plants or animals.


Iridium is found in its pure native form and in osmiridium, a natural alloy of iridium and osmium. Iridium is mined from sulfide layers in mafic igneous rocks where it is present with other platinum-group elements. Most iridium is mined in Canada, Russia and South Africa.