Iridium is a hard, brittle, silvery-white metal that belongs to the platinum family of metals. It is a chemical element represented by the chemical symbol Ir and atomic number 77. It is the most corrosion resistant metal and the second most dense element. It is also one of the rarest elements on the planet, being 40 times more rare than gold! Despite this rarity viable commercial quantities can be obtained as a by-product from nickel and copper mining. The largest commercially viable deposits of iridium are found in South Africa, Russia and Canada. Like most metals in the platinum group it was discovered after scientists determined that platinum was a new metal instead of an alloy as was first though.
Who discovered iridium?
Platinum was first identified as a new element in 1748. Scientists studying this new metal dissolved it in aqua regia (a strong acidic mixture of hydrochloric and nitric acid) and discovered a dark residue that remained. However, in these experiments there was very little residue which meant that it could not be properly studied. In 1803 British scientist Smithson Tennant studied the residue and concluded it contained a new element. He obtained a larger amount of the black residue and his continued research showed that it actually contained two new elements, iridium and osmium. He first documented this discovery in 1804. He named the element iridium after Iris, a greek goddess because many iridium salts were brightly colored.
Did you know?
The first scientist to discover a method to melt a sample of iridium was John George Children in 1813 and the first to obtain high purity iridium was Robert Hare in 1842.
Although iridium is rare on Earth, it is relatively common in meteorites.