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You probably know that famous ad diamonds are forever? But what you might not know is that scientists also appreciate diamonds and not just because they're so sparkly. It turns out that the world's biggest and most valuable diamonds may hold important clues about this planet's past. NPR's Rae Ellen Bichell reports.
RAE ELLEN BICHELL, BYLINE: Evan Smith wanted to get his hands on the world's biggest diamonds like the ones on top of royal scepters and in heavily guarded museums, but not for some nefarious get-rich-quick scheme, for science. Smith is a diamond geologist at the nonprofit Gemological Institute of America.
EVAN SMITH: The most prized of all gemstones - they're coincidentally some of the most scientifically valuable pieces of the Earth.
BICHELL: Diamonds form deep beneath the Earth in places that humans can't access and don't know that much about. And Smith thought these diamonds, which are different from others in their size and quality, might hold some clues about the planet's inner workings, if he and his colleagues could figure out where in the Earth they came from.
SMITH: It was a total mystery.
BICHELL: Smith figured that to solve that mystery, he'd have to look in the diamonds at tiny specks of mineral contamination that were sealed inside when they formed.
SMITH: You really couldn't ask for a better vessel to store something in. Diamond is the ultimate Tupperware.
BICHELL: The ultimate Tupperware. You won't sell many engagement rings with that slogan. But, for Smith, the diamonds' Tupperware quality was key. It meant the diamonds held pristine samples of the place where they'd formed, but he couldn't just knock on a royal palace door and ask to crack open the crown jewels. So instead, he got his insitute to buy eight fingernail-sized chunks of those big diamonds, the scraps left over from when the jewels were cut. After grinding, cutting and shooting lasers at them, he eventually found that many contained little bits of iron and minerals. He also took a nondestructive look at about 50 other diamonds. And as Smith wrote in the journal Science, he found that most of them contained the same unusual stuff.
SMITH: And they tell us something unique about the Earth that we've never seen before.
BICHELL: Actually, it told him two things.
SMITH: One, they tell us that these large, exceptional quality diamonds originate from extreme depths in the Earth.
BICHELL: These diamonds come from about as far under our feet as the International Space Station is above our heads - over 200 miles. That's twice as deep as normal diamonds.
SMITH: So that in itself is pretty amazing.
BICHELL: The second thing is that the diamonds had formed inside patches of liquid metal. The idea that there may be liquid metal 200 miles beneath us is at odds with the old view that the Earth's interior is a uniform rocky mixture. These diamonds show the planet and its past are a little messier than people first thought. Rae Ellen Bichell, NPR News.
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