# Are diamonds still forming? **URL:** \ **Category:** Factual Questions\ **Created:** [January 6, 2020, 9:31pm UTC](https://boards.straightdope.com/t/are-diamonds-still-forming/846044 "2020-01-06T21:31:56Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![Rick\_Kitchen](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/rick_kitchen/32/522_2.png) [@Rick\_Kitchen](https://boards.straightdope.com/u/Rick_Kitchen)\ **Post date:** [January 6, 2020, 9:31pm UTC](https://boards.straightdope.com/t/are-diamonds-still-forming/846044/1 "2020-01-06T21:31:56Z")
So diamonds are compressed coal, is that right? Are there examples in existence of coal in the process of being compressed into diamonds but it hasn’t finished yet? ---
**Author:** ![dolphinboy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/dolphinboy/32/330_2.png) [@dolphinboy](https://boards.straightdope.com/u/dolphinboy)\ **Post date:** [January 6, 2020, 9:50pm UTC](https://boards.straightdope.com/t/are-diamonds-still-forming/846044/2 "2020-01-06T21:50:34Z")
Diamonds were formed on earth a long time ago. Here is a quote from Wiki…“Most natural diamonds have ages between 1 billion and 3.5 billion years. Most were formed at depths between 150 and 250 kilometres (93 and 155 mi) in the Earth’s mantle, although a few have come from as deep as 800 kilometres (500 mi). Under high pressure and temperature, carbon-containing fluids dissolved minerals and replaced them with diamonds. Much more recently (tens to hundreds of million years ago), they were carried to the surface in volcanic eruptions and deposited in igneous rocks known as kimberlites and lamproites.” ---
**Author:** ![Senegoid](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/senegoid/32/6606_2.png) [@Senegoid](https://boards.straightdope.com/u/Senegoid)\ **Post date:** [January 7, 2020, 5:24am UTC](https://boards.straightdope.com/t/are-diamonds-still-forming/846044/3 "2020-01-07T05:24:33Z")
The same Wiki article suggests that diamonds may be abundant in places other than Earth. Future advances in space exploration may totally destroy the lucrative diamond market! > [@](#): > > High pressure experiments predict that large quantities of diamonds condense from methane into a “diamond rain” on the ice giant planets Uranus and Neptune.[68][69][70] Some extrasolar planets may be almost entirely composed of diamond. ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [January 7, 2020, 3:46pm UTC](https://boards.straightdope.com/t/are-diamonds-still-forming/846044/4 "2020-01-07T15:46:42Z")
> [@dolphinboy](#): > > Diamonds were formed on earth a long time ago. > > Here is a quote from Wiki…“Most natural diamonds have ages between 1 billion and 3.5 billion years. Most were formed at depths between 150 and 250 kilometres (93 and 155 mi) in the Earth’s mantle, although a few have come from as deep as 800 kilometres (500 mi). Under high pressure and temperature, carbon-containing fluids dissolved minerals and replaced them with diamonds. Much more recently (tens to hundreds of million years ago), they were carried to the surface in volcanic eruptions and deposited in igneous rocks known as kimberlites and lamproites.” I don’t see how that precludes new diamonds from being formed now - maybe in subduction zones, for example, where rocks containing carbon in non-diamond form may be fed into the mantle. Obviously we’d never be able to get at those diamonds anytime soon, if they are being formed there. ---
**Author:** ![Machine\_Elf](https://avatars.discourse-cdn.com/v4/letter/m/82dd89/32.png) [@Machine\_Elf](https://boards.straightdope.com/u/Machine_Elf)\ **Post date:** [January 7, 2020, 4:05pm UTC](https://boards.straightdope.com/t/are-diamonds-still-forming/846044/5 "2020-01-07T16:05:29Z")
> [@Rick\_Kitchen](#): > > So diamonds are compressed coal, is that right? Are there examples in existence of coal in the process of being compressed into diamonds but it hasn’t finished yet? Although diamonds are made of carbon, AIUI they are not simply compressed coal. The descriptions in this thread of the diamond formation process indicate that carbon-bearing fluids are the the most proximate source of carbon. It may well be that the carbon in these fluids was previously present in a coal formation a long time prior, but [despite what you may have seen,](https://www.youtube.com/watch?v=fR38h4xPfVo) I think geologists would not support the claim that diamonds are compressed coal. ---
**Author:** ![race\_to\_the\_bottom](https://avatars.discourse-cdn.com/v4/letter/r/c4cdca/32.png) [@race\_to\_the\_bottom](https://boards.straightdope.com/u/race_to_the_bottom)\ **Post date:** [January 8, 2020, 6:29am UTC](https://boards.straightdope.com/t/are-diamonds-still-forming/846044/6 "2020-01-08T06:29:02Z")
When diamonds formed \>1 billion years ago, there was no coal. ---
**Author:** ![Francis\_Vaughan](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/francis_vaughan/32/3093_2.png) [@Francis\_Vaughan](https://boards.straightdope.com/u/Francis_Vaughan)\ **Post date:** [January 8, 2020, 6:57am UTC](https://boards.straightdope.com/t/are-diamonds-still-forming/846044/7 "2020-01-08T06:57:14Z")
The diamonds from coal idea seem to have been around forever, I’m sure I was told this when I was in primary school. Then again, it wasn’t just Superman the movie, there was an original 50’s b&w Superman TV episode where he crushed a lump of coal in his hand to make a diamond. So I guess it must be true. In reality, even at the depths that coal occurs, the pressures are much too low to convert it to diamond. ---
**Author:** ![Mangetout](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mangetout/32/19_2.png) [@Mangetout](https://boards.straightdope.com/u/Mangetout)\ **Post date:** [January 8, 2020, 8:00am UTC](https://boards.straightdope.com/t/are-diamonds-still-forming/846044/8 "2020-01-08T08:00:30Z")
Carbon is the fourth most abundant element in our galaxy; I think people probably assume coal is the origin of diamonds just because coal or charcoal are the most common everyday ways that people have been encountering carbon as a recognisable material, for a long time. (sure, graphite in pencils is also common, but we’ve been busy calling that ‘lead’) ---
**Author:** ![MrDibble](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mrdibble/32/114_2.png) [@MrDibble](https://boards.straightdope.com/u/MrDibble)\ **Post date:** [January 8, 2020, 8:47am UTC](https://boards.straightdope.com/t/are-diamonds-still-forming/846044/9 "2020-01-08T08:47:35Z")
> [@Rick\_Kitchen](#): > > So diamonds are compressed coal, is that right? No, that’s not right, like everyone else has said. It’s a myth to think diamonds are compressed _anything_. They crystallised out of a hot fluid. And the most likely source of their carbon was inorganic carbonate rocks of the early Earth, or primordial carbon that was in the mantle from formation. ---
**Author:** ![armedmonkey](https://avatars.discourse-cdn.com/v4/letter/a/d6d6ee/32.png) [@armedmonkey](https://boards.straightdope.com/u/armedmonkey)\ **Post date:** [January 8, 2020, 10:35am UTC](https://boards.straightdope.com/t/are-diamonds-still-forming/846044/10 "2020-01-08T10:35:34Z")
> [@race\_to\_the\_bottom](#): > > When diamonds formed \>1 billion years ago, there was no coal. Diamonds are just a form of carbon, but, oddly now that I think about it, this is a very interesting question. Picture a carbon cycle - but I’m talking about the _element_ here. It gets bounced around in rocks and biological systems and what not… but if it crystallizes into a diamond, that’s pretty freaking stable. It _breaks_ the cycle. That carbon atom doesn’t cycle through anymore. Now, there is _plenty_ of carbon of Earth, so it’s not like biological life is ever going to run out of the stuff, but it is kinda interesting to note that there is a “sink” in the carbon cycle, and it’s diamonds. ---
**Author:** ![DPRK](https://avatars.discourse-cdn.com/v4/letter/d/4491bb/32.png) [@DPRK](https://boards.straightdope.com/u/DPRK)\ **Post date:** [January 8, 2020, 10:58am UTC](https://boards.straightdope.com/t/are-diamonds-still-forming/846044/11 "2020-01-08T10:58:01Z")
You haven’t broken the cycle, since diamonds are unstable at atmospheric pressure and will spontaneously un-form and turn to graphite. ---
**Author:** ![armedmonkey](https://avatars.discourse-cdn.com/v4/letter/a/d6d6ee/32.png) [@armedmonkey](https://boards.straightdope.com/u/armedmonkey)\ **Post date:** [January 8, 2020, 11:26am UTC](https://boards.straightdope.com/t/are-diamonds-still-forming/846044/12 "2020-01-08T11:26:35Z")
> [@DPRK](#): > > You haven’t broken the cycle, since diamonds are unstable at atmospheric pressure and will spontaneously un-form and turn to graphite. Diamonds do not become graphite. Just… no. Diamonds are not unstable at atmospheric pressure. Nobody’s engagement ring is going to turn into pencil lead. Simply put, just no. ---
**Author:** ![MrDibble](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mrdibble/32/114_2.png) [@MrDibble](https://boards.straightdope.com/u/MrDibble)\ **Post date:** [January 8, 2020, 11:27am UTC](https://boards.straightdope.com/t/are-diamonds-still-forming/846044/13 "2020-01-08T11:27:38Z")
> [@DPRK](#): > > You haven’t broken the cycle, since diamonds are unstable at atmospheric pressure and will spontaneously un-form and turn to graphite. Diamond is metastable at STP, there’s not a lot of spontaneous decomposition happening. At normal surface conditions, diamond will last. Of course, nothing on the Earth’s surface stays at STP for all that long. ---
**Author:** ![What\_Exit](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/what_exit/32/10652_2.png) [@What\_Exit](https://boards.straightdope.com/u/What_Exit)\ **Post date:** [January 8, 2020, 11:50am UTC](https://boards.straightdope.com/t/are-diamonds-still-forming/846044/14 "2020-01-08T11:50:26Z")
> [@Senegoid](#): > > The same Wiki article suggests that diamonds may be abundant in places other than Earth. Future advances in space exploration may totally destroy the lucrative diamond market! It is an artificial market, it deliberately keeps supply tight. It has survived lab made diamonds which are diamonds. So the scummy diamond industry is probably pretty safe from space diamonds. ---
**Author:** ![armedmonkey](https://avatars.discourse-cdn.com/v4/letter/a/d6d6ee/32.png) [@armedmonkey](https://boards.straightdope.com/u/armedmonkey)\ **Post date:** [January 8, 2020, 11:51am UTC](https://boards.straightdope.com/t/are-diamonds-still-forming/846044/15 "2020-01-08T11:51:37Z")
> [@MrDibble](#): > > Of course, nothing on the Earth’s surface stays at STP for all that long. Which, oddly, gets back to my idle observation about geological carbon. If we assume that the supply is finite, then, well, there is a non zero loss of usable carbon to diamonds due to geological processes. It sure as hell isn’t significant, but it is non-zero. So as to the OP: The Planet Earth will always form diamonds, all it needs is carbon, which is plentiful. Not just in coal, or biological systems. the element is everywhere. ---
**Author:** ![MrDibble](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mrdibble/32/114_2.png) [@MrDibble](https://boards.straightdope.com/u/MrDibble)\ **Post date:** [January 8, 2020, 12:10pm UTC](https://boards.straightdope.com/t/are-diamonds-still-forming/846044/16 "2020-01-08T12:10:42Z")
> [@armedmonkey](#): > > Which, oddly, gets back to my idle observation about geological carbon. If we assume that the supply is finite, then, well, there is a non zero loss of usable carbon to diamonds due to geological processes. It sure as hell isn’t significant, but it is non-zero. You’d have to balance it against the incoming carbon in carbonaceous meteors before you can say if there’s a loss or gain… ---
**Author:** ![Frankenstein\_Monster](https://avatars.discourse-cdn.com/v4/letter/f/ccd318/32.png) [@Frankenstein\_Monster](https://boards.straightdope.com/u/Frankenstein_Monster)\ **Post date:** [January 8, 2020, 1:11pm UTC](https://boards.straightdope.com/t/are-diamonds-still-forming/846044/17 "2020-01-08T13:11:10Z")
> [@Mangetout](#): > > I don’t see how that precludes new diamonds from being formed now - maybe in subduction zones, for example, where rocks containing carbon in non-diamond form may be fed into the mantle. Obviously we’d never be able to get at those diamonds anytime soon, if they are being formed there. So I don’t see anything or anyone contradicting this idea? It takes (or took) a billion+ years for diamonds to migrate to the surface from where they form(ed). I don’t see what has changed so that diamonds would no longer form. Although maybe their migration to the surface has slowed or stopped (less geological activity). So can one confidently state that diamonds are still forming in the earth’s mantle? ---
**Author:** ![Jasmine](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jasmine/32/2964_2.png) [@Jasmine](https://boards.straightdope.com/u/Jasmine)\ **Post date:** [January 8, 2020, 1:20pm UTC](https://boards.straightdope.com/t/are-diamonds-still-forming/846044/18 "2020-01-08T13:20:59Z")
It’s a large planet. I think we can safely assume that there are places where diamonds are in the process of being created. As mentioned, they are much more plentiful than many people believe because the Diamond Cartel manipulates prices by controlling the diamonds released for sale. It used to be solely De Beers that controlled the market, but now it is a group. A very interesting article: [\*\*The International Diamond Cartel \*\*](https://are.berkeley.edu/~sberto/debers.pdf) ---
**Author:** ![What\_Exit](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/what_exit/32/10652_2.png) [@What\_Exit](https://boards.straightdope.com/u/What_Exit)\ **Post date:** [January 8, 2020, 1:30pm UTC](https://boards.straightdope.com/t/are-diamonds-still-forming/846044/19 "2020-01-08T13:30:07Z")
> [@Jasmine](#): > > … > A very interesting article: > > [\*\*The International Diamond Cartel \*\*](https://are.berkeley.edu/~sberto/debers.pdf) That is a good, succinct Power Point display on the issue. Quick read, covering enough details. ---
**Author:** ![MrDibble](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/mrdibble/32/114_2.png) [@MrDibble](https://boards.straightdope.com/u/MrDibble)\ **Post date:** [January 8, 2020, 1:57pm UTC](https://boards.straightdope.com/t/are-diamonds-still-forming/846044/20 "2020-01-08T13:57:11Z")
> [@Frankenstein\_Monster](#): > > t takes (or took) a billion+ years for diamonds to migrate to the surface from where they form(ed) Not exactly. The emplacement was more-or-less instantaneous in geological time. Kimberlite eruptions were _[powerful](https://en.wikipedia.org/wiki/Volcanic_pipe)_. Supersonic explosion-powerful > [@](#): > > I don’t see what has changed so that diamonds would no longer form. Although maybe their migration to the surface has slowed or stopped (less geological activity). > > So can one confidently state that diamonds are still forming in the earth’s mantle? Not likely. If they were still forming, we’d see them in kimberlites. But the gap in age between the youngest diamonds in kimberlites and the actual kimberlites themselves is big enough - hundreds of millions of years - that it seems like \*something \*stopped mantle diamond formation (or at least - \*that \*kind of diamond formation. microdiamonds and the like \*are \*still being formed). Possibly a change in the mantle heat flow or similar. [Next page](https://boards.straightdope.com/t/are-diamonds-still-forming/846044.md?page=2)