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Earth Science

Is the Earth's Mantle Full of Diamonds? (gizmodo.com) 109

Posted by BeauHD 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.
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Is the Earth's Mantle Full of Diamonds? More

Is the Earth's Mantle Full of Diamonds?

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  • Yes. (Score:3)

    by xxxJonBoyxxx ( 565205 ) on Tuesday July 17, 2018 @10:33PM (#56966232)
    Yes.

    • 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.

      • Actually, no.

      • Re:Yes. (Score:5, Informative)

        by TheRealQuestor ( 1750940 ) on Tuesday July 17, 2018 @11:55PM (#56966436)
        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.

        • Re:Yes. (Score:5, Insightful)

          by Bonker ( 243350 ) on Wednesday July 18, 2018 @01:03AM (#56966538)

          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..

          • the 8th element (Score:1)

            by Anonymous Coward

            Element 8 is oxygen, and no, that's not rare at all. It forms a large part of the Earth's mantle, crust and oceans.

        • Diamonds might not be that rare, but the manual work to make them marketable is a rare competence.

          • Re:Yes. (Score:5, Informative)

            by thegarbz ( 1787294 ) on Wednesday July 18, 2018 @02:49AM (#56966740)

            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.

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

          • Except that you can't easily resell those heirlooms, even at the current market price! Jewelry stores often buy diamonds on consignment from wholesalers. And the wholesalers don't want your diamond either. So it's already cut, it looks perfect, but you can only sell the thing for about 25% of what seems to be the market price.

            The demand for new diamonds is artificially created by marketing, and such a market didn't exist for the average public more than about a century ago. The idea of spending X% of your

        • Re: (Score:3)

          by SeaFox ( 739806 )

          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.

          • Want to bet that DeBeers would find another way to protect their de facto monopoly? It's not like they are the only ones who could sell diamonds due to availability, but curiously, some reason exists...

            • Why settle for a common dirt diamond when you can get a top of the line Tiffany's diamond cluster that comes with an authenticated pedigree certificate showing that they came from the most exclusive slave mines, each hand polished on the bosoms of the most highly paid reality TV starlets?

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

        • Similarly you think your money is worth something while others create them out of nothing at the volume of whatever amount of trillions and then buy something which is actually more limited for the profits they make.

  • Why dig down 120 kilometer if you make them yourself ? https://www.youtube.com/watch?... [youtube.com]

  • What the headline.. (Score:2, Insightful)

    by Anonymous Coward

    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...

  • 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.

  • Hmmm (Score:3)

    by hcs_$reboot ( 1536101 ) on Tuesday July 17, 2018 @11:03PM (#56966330)
    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.

    • Re:Hmmm (Score:4, Insightful)

      by Gavagai80 ( 1275204 ) on Tuesday July 17, 2018 @11:25PM (#56966378) Homepage

      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.

      • Would that be diamonds or glass or whatever, "enthusiastic" refers to how definitive and assured the conclusion is made, at depths we know almost nothing.

        • Re: (Score:1)

          by Anonymous Coward

          Well, we know quite a lot about the behaviour of sound at those depths - "know almost nothing" is pretty vague and useless. And carbon is common and the conditions at those depths are conducive to diamond formation, so this isn't the huge leap you seem to think it is. Moreover, "glass" is a pretty general name for a lot of materials, most of which won't behave down there as they do up here, so seems unlikely they'd be criticized for "oops forgot to test for 'glass'".

          "Definitive and Assured" - doesn't sound

      • While I don't think drilling on Mars for diamonds makes any sense I wonder how hard it would be to drill deeply with the reduced gravity and colder interior?

    • Re: (Score:1)

      by Anonymous Coward

      The researchers studied an observed anomaly, formulated a hypothesis, and did some modeling to see whether the hypothesis was plausible and the conditions under which it might hold. Sounds like science to me.

    • Re: (Score:2, Informative)

      by Anonymous Coward

      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

  • Of course it is! (Score:5, Insightful)

    by DontBeAMoran ( 4843879 ) on Tuesday July 17, 2018 @11:11PM (#56966344)

    Haven't you guys seen "The Core"?

  • Only 75 miles? (Score:1)

    by Anonymous Coward

    So all you have to do is figure out a way to mine at a depth 30 times
    deeper than the worlds deepest mine. [wikipedia.org]
    Piece of cake.

    • Plus conditions change... pressure (40 kbar), temperature ...

    • Re: (Score:3)

      by jwhyche ( 6192 )

      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.......

  • Cratons? (Score:3)

    by 93 Escort Wagon ( 326346 ) on Tuesday July 17, 2018 @11:55PM (#56966438)

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

    • Tom Cruise??

    • Re: (Score:1)

      by koomba ( 2882339 )
      Pretty common geological term, if you took any high school level or higher geology class, you would know the term. It's nothing complicated.

      A craton is basically an old, stable part of the earth's crust, which generally make up the core of all the major tectonic plates. It's the part that has survived the cycles of subduction, so it's usually roughly in the center of the tectonic plate. For example, the Canadian Shield is the craton that makes up the core of the North American plate, and has some of the

  • De Beers (Score:2)

    by tsa ( 15680 )

    The De Beers company probably has known this since the 1950s or so.

  • But if you dug all those shiny crystals their value would rapidly approach zero.

  • I repeat: Lucy is here....and we thought we need to travel 5.2 AU to get to her :)

  • of a starkiller base

  • My God... (Score:3)

    by zifn4b ( 1040588 ) on Wednesday July 18, 2018 @07:43AM (#56967440)
    ...It's full of diamonds!
  • Some years ago I read way deep down there are diamonds the size of watermelons. By the time they make it to surface (million years or more?) they are broken up into much smaller pieces. Imagine a diamond that big, how much would it weigh? What about polishing it and trim it? Be a damn shame if a jeweler intended to trim the edge but hit it in such a way it shatters into little pieces like a car rear window.
  • Comment removed based on user account deletion
  • Earth keeps its diamonds in the credenza.

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