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Is the Earth's Mantle Full of Diamonds? (gizmodo.com)

Posted by BeauHD on from the journey-to-the-center-of-the-earth dept.

An anonymous reader quotes a report from Gizmodo: Scientists' models show that sound waves seem to travel too quickly through the old, stable cores of continents, called "cratons," which extend deep into the mantle at depths around 120 to 150 kilometers (75 to 93 miles). Through observations, experiments, and modeling, one team figured that a potential way to explain the sound speed anomaly would be the presence of a lot of diamonds, a medium that allows for a faster speed of sound than other crystals. Perhaps the Earth is as much as 2 percent diamonds by volume, they found. Scientists have modeled the rock beneath continents through tomography, which you can think of as like an x-ray image, but using sound waves. But sound-wave velocities of around 4.7 kilometers per second (about 10,513 mph) are faster than sound-wave velocities in other kinds of minerals beneath the crust, according to the paper in the journal Geochemistry, Geophysics, Geosystems.

The researchers realized that if the regions had either 3 percent diamonds by volume or 50 percent of a rock formed at high pressure and temperature called eclogite, it would enable the sound speeds they observed. But both of those numbers seemed too high, based on observations of the minerals that end up on the Earth's surface: diamond-containing rocks called kimberlites. The researchers compromised and figured that 20 percent eclogite and 2 percent diamonds could explain the high velocities. The diamonds could be sprinkled as crystals found uniformly throughout the cratons.

21 of 109 comments (clear)

  1. Yes. by xxxJonBoyxxx · · Score: 2

    Yes.

    1. Re:Yes. by JMJimmy · · Score: 2

      So what you're really saying is that there are 21 600 000 000 cubic kilometers worth of diamonds and they really are just worthless rocks - not worth the thousands people spend on them. Yes, it makes perfect sense.

    2. Re:Yes. by TheRealQuestor · · Score: 5, Informative

      Diamonds AREN'T that rare which is why resale is so bad on them. The only reason we think they are rare is because De Beers Consolidated Mines, Ltd wants us to BELIEVE they are.

    3. Re:Yes. by Bonker · · Score: 4, Insightful

      IANAGP/C... ...BUUUT, the 8th element by atomic number just ain't that rare in the cosmos.The general asshattery of the DeBeers family and corp aside, the fact that we've known about one of its molecular allotropes for most of our written history SHOULD tell us that allotrope ain't that rare on Earth, either. Yeah, you need special conditions to press a 2-d lattice into a 3-d lattice, but we're doing that in labs with, literally, waste gasses from sewage. The fact that uur pressure-cooker of a planet's interior does the same thing should come as a surprise to small children and the illiterate..

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    4. Re:Yes. by thegarbz · · Score: 5, Informative

      Errr no. It's not very specialised at all. Cutting gems is quite easy. A month or two of on the job training and you'll be cranking out some beauties. Getting trained up to the point of being able to cut expensive diamonds is not difficult feat and doesn't require any training that you don't get on the spot.

    5. Re:Yes. by SeaFox · · Score: 2

      Diamonds AREN'T that rare which is why resale is so bad on them.

      It's also why it doesn't matter if the Earth's mantle is full of diamonds. If it is, and we were to suddenly get access to them, we wouldn't be rich because we would have just crashed the diamond market.

    6. Re:Yes. by gravewax · · Score: 2

      ahhhh no, it is a very common skill. Again you have been listening to De Beers PR BS.

    7. Re:Yes. by Anonymous Coward · · Score: 3, Interesting

      you don't start on expensive ones, you start on crappy flawed ones, it isn't expensive to learn or particularly difficult, one of my friends now does it professionally. Nowdays it is easier than ever with computers and lasers to do all the measurements to work out the best way to cut and shape it, one of the difficult skills used to be that, now that skill is barely necessary at all.

    8. Re:Yes. by JMJimmy · · Score: 2

      The diamond market is already being propped up - multiple massive deposits in Russia aren't being mined.

  2. What the headline.. by Anonymous Coward · · Score: 2, Insightful

    So the answer to the head line is NO, it is not full, it is maybe 2% by volume. Utah beer has more alcohol than that...

  3. I have a different hypothesis by mnemotronic · · Score: 5, Funny

    The lithospheric mantle is composed of politicians; an incredibly dense material. Sound waves and thermal gradients pass easily through this layer. Money, on the other hand, is readily absorbed by the same material. Strangely, truth is reflected but with, as yet, explainable phase shifts or distortions.

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  4. Hmmm by hcs_$reboot · · Score: 2

    So the only explanation to "sound waves seem to travel too quickly through the old, stable cores of continents" is "the presence of a lot of diamonds". A bit over enthusiastic imo.

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    1. Re:Hmmm by Gavagai80 · · Score: 3, Insightful

      Enthusiastic? Nobody is going to commercially mine the mantle for diamonds. Even the deepest oil wells are only a few miles. At any rate, diamonds are the most common gem on the surface.

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    2. Re:Hmmm by Anonymous Coward · · Score: 2, Informative

      So the only explanation to "sound waves seem to travel too quickly through the old, stable cores of continents" is "the presence of a lot of diamonds". A bit over enthusiastic imo.

      Well, let's ask the experts:

      These constraints suggest that diamond and eclogite are the most likely high-Vs candidates to explain the observed velocities, but matching the high shear-wave velocities requires either a large proportion of eclogite (>50 vol.%) or the presence of up to 3 vol.% diamond, with the exact values depending on peridotite and eclogite compositions and the geotherm

      So the experts show that your claim is false, diamond isn't the only explanation. It is one of many explanations, and is one of two that are the most likely out of all of them.

      You are going to need to show far more evidence for your claim of "the only explanation" than nothing before it is seriously entertained.

      For what it's worth, I do agree that your claim, a seemingly baseless one at the moment, is very overly enthusiastic. But I'd be willing to change that opinion if you'd share the reasoning and/or evidence for your claim that diamonds are the only option.

  5. Re:Diamonds from the microwave by hcs_$reboot · · Score: 2

    Five long minutes of pure BS.

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  6. Of course it is! by DontBeAMoran · · Score: 5, Insightful

    Haven't you guys seen "The Core"?

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  7. Re:No. by Aristos+Mazer · · Score: 3, Funny

    Or the core of Earth *is* De Beers' vault?

  8. Cratons? by 93+Escort+Wagon · · Score: 2

    Sounds like one of those weird creatures L Ron Hubbard came up with.

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  9. Re:No. by Opportunist · · Score: 2

    Well, they have been known to create artificial scarcity by limiting supply due to stockpiling...

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  10. My God... by zifn4b · · Score: 2

    ...It's full of diamonds!

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  11. Re:Only 75 miles? by jwhyche · · Score: 2

    A better plan would be to find a large iron asteroid in the outer solar system. Then direct it around the sun a few times to pick up speed. Then slam it into the planet. I'm picturing a rifle bullet through a water melon here. That way instead of just the diamonds you can get at all the inner earths goodies.

    Of course I think there might be another problem with this plan. I just can't think of it right now.......

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