# iridium

/ˌɪˈɹɪdiəm/ (US) · /ɪɹˈɪdiəm/ (UK) · CEFR C1 · Noun

Source: https://englishreference.com/word/iridium
Updated: 2026-05-28

## Definition

a very hard and heavy metal that is almost impossible to melt. It is one of the rarest elements on Earth and is often used in special tools and jewelry.

For teachers: a hard, silvery-white, corrosion-resistant transition metal of the platinum group. It is the most corrosion-resistant and the second-densest element in the periodic table.

## Examples

- The scientist used a tiny amount of iridium to make the pen tip.
- Because of its extreme durability, iridium is often alloyed with platinum to create spark plugs for high-performance engines.
- The geological layer rich in iridium found at the Cretaceous-Paleogene boundary provides strong evidence for the impact hypothesis regarding the extinction of the dinosaurs.

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From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.