This sediment layer is enriched in the rare metal iridium and other elements that are relatively abundant in a meteorite but very rare in the crust of Earth.

这一沉积层富含稀有金属铱，以及其他在陨石中较丰富而在地壳中十分罕见的元素。

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It is an increased area of low thick clouds, the type that reflects a rare portion of solar energy back to space and cools the Earth.

它是一片变大的低厚云层，这种云层将少量的太阳能反射回太空，为地球降温。

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These decisions were made at PRAYON to develop rare earth.

这些决定是在普拉永公司做出的，目的是开发稀土。

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"Molycorp is the western hemisphere's only producer of rare earth products."

VOA: special.2010.10.15

The United States has shuttered the vast majority its rare earth mines and now imports over 90% of the rare earth material needed for both economic purposes as well as weaponry.

CENTERFORSECURITYPOLICY: Center For Security Policy

Rare earth minerals are now an important national policy issue as politicians and media pundits discover the fact that rare earth minerals are required to produce things like electric cars, wind turbines, guided missiles, and iPods.

FORBES: The Money Man Behind America's Rare Earth Minerals

Virtually all U.S. advanced electronics, as eminent chemist Arthur Robinson reported last month in his newsletter Access to Energy, are dependent on rare earth elements used to enhance the performance of microchips and held in a near global monopoly by the Chinese firm Baotou Steel Rare-Earth Hi-Tech Company in Mongolia.

WSJ: George Gilder: Why Antagonize China?