irid·​i·​um | \ i-ˈri-dē-əm How to pronounce iridium (audio) \

Definition of iridium

: a rare silver-white hard brittle very heavy metallic element — see Chemical Elements Table

Examples of iridium in a Sentence

Recent Examples on the Web

The official object that defines the mass of a kilogram is a tiny, 139-year-old cylinder of platinum and iridium that resides in a triple-locked vault near Paris. Clara Moskowitz, Scientific American, "Redefining the Kilogram," 1 Nov. 2018 Their key piece of evidence is an oddly high amount of the metal iridium in what’s known as the Cretaceous-Paleogene, or K-Pg, layer—the geologic boundary zone that seems to cap any known rock layers containing dinosaur fossils. Victoria Jaggard, National Geographic, "Why did the dinosaurs go extinct?," 31 July 2019 Iridium-192 is a radioactive isotope of the chemical element iridium, according to the U.S. National Center for Biotechnology Information. Washington Post, "Prime minister resigns after Hague summons," 20 July 2019 Dubbed Le Grande K, or Big K, this lonely hunk of platinum and iridium has defined mass around the globe for more than a century—from bathroom scales to medical lab balances. Robert Rathe, National Geographic, "The kilogram is forever changed. Here's why that matters.," 20 May 2019 To increase their stability, the prototypes were reforged in 1889 out of a platinum-iridium alloy and stowed under lock and key. Robert Rathe, National Geographic, "The kilogram is forever changed. Here's why that matters.," 20 May 2019 Geologists soon found a similar iridium layer at the same geological strata in other parts of the world. Nina Burleigh, Newsweek, "We Can Save Ourselves From Earth-Killing Asteroids, But Someone Has to Pay," 11 June 2015 Iron meteorites: Typically consist of approximately 90 to 95% iron, with the remainder comprised of nickel and trace amounts of heavy metals, including iridium, gallium and sometimes gold. Perry A. Farrell, Detroit Free Press, "Which type of meteorite landed in Michigan? NASA 90% sure it knows," 17 Jan. 2018 In 2011, researchers led by Richard Masel, a chemist and CEO of Dioxide Materials in Boca Raton, Florida, tested a setup with silver and iridium oxide catalysts and a liquid electrolyte to promote the CO2 to CO reaction. Robert Service, Science | AAAS, "Two new ways to turn ‘garbage’ carbon dioxide into fuel," 1 Sep. 2017

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'iridium.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

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First Known Use of iridium

1804, in the meaning defined above

History and Etymology for iridium

Greek īrid-, îris "rainbow, iridescent halo around the moon, a flame, etc., iris entry 1" + New Latin -ium -ium; from the colors produced by dissolving it in hydrochloric acid

Note: The word iridium was introduced by the English chemist Smithson Tennant (1761-1815) in Philosophical Transactions of the Royal Society, 1804, Part II, p. 414: "As it is necessary to give some name to bodies which have not been known before, and most convenient to indicate by it some characteristic property, I should incline to call this metal Iridium, from the striking variety of colours which it gives, while dissolving in marine acid." See also osmium.

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Last Updated

26 Sep 2019

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Time Traveler for iridium

The first known use of iridium was in 1804

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More Definitions for iridium


irid·​i·​um | \ i-ˈri-dē-əm How to pronounce iridium (audio) \

Kids Definition of iridium

: a hard brittle heavy metallic chemical element


irid·​i·​um | \ ir-ˈid-ē-əm How to pronounce iridium (audio) \

Medical Definition of iridium

: a silver-white hard brittle very heavy metallic element of the platinum group used especially in hardening platinum for alloys (as for surgical instruments) symbol Ir — see Chemical Elements Table

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Spanish Central: Translation of iridium

Nglish: Translation of iridium for Spanish Speakers Encyclopedia article about iridium

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