iridium

American  

[ih-rid-ee-uhm, ahy-rid-] / ɪˈrɪd i əm, aɪˈrɪd- /

noun

Chemistry.

1. a precious metallic element resembling platinum: used in platinum alloys and for the points of gold pens. Ir; 192.2; 77; 22.4 at 20°C.

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iridium British  

/ ɪˈrɪd-, aɪˈrɪdɪəm /

noun

1. a very hard inert yellowish-white transition element that is the most corrosion-resistant metal known. It occurs in platinum ores and is used as an alloy with platinum. Symbol: Ir; atomic no: 77; atomic wt: 192.22; valency: 3 or 4; relative density: 22.42; melting pt: 2447°C; boiling pt: 4428°C

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iridium Scientific  

/ ĭ-rĭd′ē-əm /

1. A rare, whitish-yellow element that is the most corrosion-resistant metal known. It is very dense, hard, and brittle, and is is used to make hard alloys of platinum for jewelry, pen points, and electrical contacts. Atomic number 77; atomic weight 192.2; melting point 2,410°C; boiling point 4,130°C; specific gravity 22.42 (at 17°C); valence 3, 4.

2. See Periodic Table

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Closer Look

In 1978 geologist Walter Alvarez discovered a high concentration of iridium in a layer of clay that had formed between the Mesozoic and Cenozoic eras, a period about 65 million years ago during which dinosaurs and many other organisms became extinct. This finding was significant as iridium is rare at Earth's surface (an unusually high concentration is called an iridium anomaly). Most surface iridium is thought to come from dust created when meteors disintegrate in the atmosphere or collide with Earth. Alvarez's father, the physicist Luis Alvarez, suggested that the iridium might have come from the impact of a meteor about 10 km (6.2 mi) across. Such an impact would have caused an enormous explosion, sending huge clouds of dust into the atmosphere. The dust, blocking out the Sun and causing extensive acid rain, would have triggered a worldwide ecological disaster. Many scientists think that such a disaster caused the extinction of the dinosaurs and at least 70 percent of all other species alive at the time, including most of Earth's land plants. Geologists have since found iridium deposits in rocks of a similar age in more than 100 places worldwide. Scientists in the early 1990s identified a large impact crater in the Yucatán peninsula of central Mexico that is the same age as the iridium deposit found by Alvarez. It is 200 km (125 mi) wide and may have been caused by the same impact.

Etymology

Origin of iridium

1804; < Latin īrid-, stem of īris rainbow ( iris ) + -ium; so named from its iridescence when dissolved in hydrochloric acid

Example Sentences

This layer is also rich in platinum, iridium, metallic melt particles, shocked quartz, and fused minerals known as meltglass.

From Science Daily

Until now, many of these light-driven processes depended on ruthenium, osmium, or iridium -- elements that are costly, scarce, and create environmental concerns when mined.

From Science Daily

"There is actually only one catalyst -- iridium oxide -- that remains stable."

From Science Daily

The current study does just that by combining manganese with iridium.

From Science Daily

The sample is then coated with a thin layer of iridium metal to make it conductive.

From Salon