I is for Iridium

Iridium was discovered in 1803 and is part of the platinum group of metals.  It’s hard, brittle and silvery white.  It’s also the most corrosive resistant metal.  Iridium is one of the rarest metals in Earth’s crust.  Iridium metal is used when high corrosion existence at high temperatures is needed, such as high performance spark plugs.

Iridium is found in meteorites in much higher abundance than in Earth’s crust.  It’s believed this mineral was in the large meteorite that crashed into Earth thousands of years ago and caused the extinction of the dinosaurs.

A troy ounce of iridium - photo courtesy of Wikipedia

Because of iridium’s high melting point, it makes this metal very hard to machine or form.  Iridium is the most non corrosive mineral known.  It isn’t even corroded by acid, molten medals or silicates.  It can be attacked by some molten salts such as sodium cyanide or potassium cyanide.

The largest primary reserves of iridium are found on Africa, Russia and Canada.

Certain long-life aircraft parts are made from an iridium alloy.  Other alloys of iridium are used in deep water pipes.  It’s also used in x-ray telescopes.  The radioisotope iridium-192 is used as a source of gamma radiation for treating some types of cancer.