Which precious metal is named after the Latin word for “rainbow”? Iridium is the answer. Its name comes through the Latin iris, meaning rainbow, from the Greek Iris, the rainbow goddess.
Smithson Tennant named iridium after examining the vividly colored compounds produced from residues of platinum ore. The element was identified in 1803, alongside osmium, in material that resisted dissolution in strong acids. Iridium itself is silvery-white, so the rainbow reference describes its compounds rather than the bulk metal’s appearance.
Iridium is a platinum-group metal with the symbol Ir and atomic number 77. It is extraordinarily resistant to corrosion and ranks among the densest naturally occurring elements. Those properties make it useful in demanding applications such as spark plugs, high-temperature crucibles, and semiconductor manufacturing.
A common mix-up is rhodium, whose name is associated with the Greek word for rose because of the color of some of its salts. Osmium, another neighboring platinum-group element, was named for the Greek word for smell.