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'''Iridium''' is an [[element]] in the [[transition metal]]s class of the [[periodic table of the elements|periodic table]].  It is hard and lustrous, and is perhaps the most corrosion-resistant metal known.  It has the second-highest density of all elements, after [[osmium]].

'''Iridium''' is an [[element]] in the [[transition metal]]s class of the [[periodic table of the elements|periodic table]].  It is hard and lustrous, and is perhaps the most corrosion-resistant metal known.  It has the second-highest density of all elements, after [[osmium]].

An alloy of [[platinum]] and iridium was used in the international standard [[International_System_of_Units#Meter|meter]] bar, before the standard was changed in 1960.  A similar alloy is still used in the international standard [[International_System_of_Units#Kilogram|kilogram]].

An alloy of [[platinum]] and iridium was used in the international standard [[International_System_of_Units#Meter|meter]] bar, before the standard was changed in 1960.  A similar alloy is still used in the international standard [[International_System_of_Units#Kilogram|kilogram]]. An alloy of 90% platinum and 10% iridium is widely used in both the jewelry and chemical industries, because it is strong, hard, beautiful, and impervious to almost all chemicals even at very high temperatures.

Iridium has provided evidence for a leading theory explaining the extinction of the dinosaurs.  There is a worldwide geologic layer, enriched in iridium, apparently deposited about 65 million years ago.  This was the time of the cretaceous/tertiary boundary, when many species, most famously the dinosaurs, became extinct.  Asteroids have a higher iridium content than the Earth's crust, suggesting that the layer was caused by widespread dispersal of matter from a comet or asteroid strike.  Many scientists believe that such a strike, or several strikes, caused the cretaceous/tertiary boundary event, and that the (now buried) Chicxulub crater in what is now the Yucatan peninsula of Mexico was the impact site.  The debris from the impact may have blocked sunlight, damaging the food chain.

Iridium does not have many "everyday" uses, but a few common ones are:

The Chicxulub impact is not the only theory behind the extinction.  Another theory is that it was caused by particularly noxious volcanos in what is now India.

- Spark plugs.

In any case, the iridium did not kill the dinosaurs; the worldwide darkening of the skies did.

 

 

- Electrical contacts.

[[Category:Elements]]

[[Category:Elements]]