Iridium

Iridium is a chemical element that has the symbol Ir and atomic number 77. A dense, very hard, brittle, silvery-white transition metal of the platinum family, iridium is used in high-strength alloys that can withstand high temperatures and occurs in natural alloys with platinum or osmium. Iridium is notable for being the most corrosion-resistant element known. It is used in high-temperature apparatus, electrical contacts, and as a hardening
agent for platinum. The principal use of iridium is as a hardening
agent in platinum alloys. Other uses: Crucibles and devices that require high temperatures. Electrical contacts (notable example: Pt-Ir spark plugs). Osmium-iridium alloys are used for compass bearings. Iridium is commonly used in complexes like Ir(mppy)3 and other complexes in polymer LED technology to increase the efficiency from 25% to almost 100% due to triplet harvesting. Used in high-dose-radiation therapy for the treatment of prostate and other forms of cancer Iridium is used as a catalyst for carbonylation of methanol to produce acetic acid Iridium is
used in supercolliders in the production of antimatter, specifically antiprotons.