# Couild a large diamond be made from many smaller ones? **URL:** \ **Category:** Factual Questions\ **Created:** [February 26, 2008, 7:20pm UTC](https://boards.straightdope.com/t/couild-a-large-diamond-be-made-from-many-smaller-ones/439264 "2008-02-26T19:20:30Z")\ **Posts on this page:** 9\ **Page:** 1
**Author:** ![solkoe](https://avatars.discourse-cdn.com/v4/letter/s/919ad9/32.png) [@solkoe](https://boards.straightdope.com/u/solkoe)\ **Post date:** [February 26, 2008, 7:20pm UTC](https://boards.straightdope.com/t/couild-a-large-diamond-be-made-from-many-smaller-ones/439264/1 "2008-02-26T19:20:30Z")
Is it possible to take many small diamond fragments, melt them and then recrystallize them into a larger diamond? I assume it is possible to reach that temperature as the melting point of diamond is known. It would have to take place in a vaccum as well as carbon will easily oxidize at this temperature. ---
**Author:** ![Sunspace](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/sunspace/32/1250_2.png) [@Sunspace](https://boards.straightdope.com/u/Sunspace)\ **Post date:** [February 26, 2008, 7:27pm UTC](https://boards.straightdope.com/t/couild-a-large-diamond-be-made-from-many-smaller-ones/439264/2 "2008-02-26T19:27:52Z")
Can you melt carbon… ever? I thought it just sublimed. Now, if you want to _build_ a big diamond from smaller, I imagine something like [Jon Kuhn’s glass sculptures](http://www.kuhnstudio.com/photogalleries-t.htm). ---
**Author:** ![CalMeacham](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/calmeacham/32/35_2.png) [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)\ **Post date:** [February 26, 2008, 7:33pm UTC](https://boards.straightdope.com/t/couild-a-large-diamond-be-made-from-many-smaller-ones/439264/3 "2008-02-26T19:33:56Z")
1.) If you take small pieces of diamond and try to asemble them into a larger diamond, it’s 99.999% certain that the crystal planes won’t line up, and so you won’t have a big single crystal. This won’t have as much strength along the lines where the pieces join, and will come apart easily. I used to grow crystals, and it’s appallingly easy to grow a polycrystalline mass instead of a single crystal. Polycrystalline masses don’t look anywhere near as pretty as single crystals, and they do come apart easily. 2.) are you suggesting melting the edges of the pieces to stick things together? I don’t think you can melt diamond. You might be able to squeeze them together under high temperature and pressure and get them to stick. To say that this is not an easy thing to do, in any case, is an understatement. ---
**Author:** ![Squink](https://avatars.discourse-cdn.com/v4/letter/s/b5e925/32.png) [@Squink](https://boards.straightdope.com/u/Squink)\ **Post date:** [February 26, 2008, 7:45pm UTC](https://boards.straightdope.com/t/couild-a-large-diamond-be-made-from-many-smaller-ones/439264/4 "2008-02-26T19:45:31Z")
According to this [phase diagram for carbon](http://members.tm.net/lapointe/Carbon_Phase_Diagram.gif), you’ll need to melt your diamonds at 1000°C and 5,000,000 psi to favor diamond formation over graphite formation. ---
**Author:** ![solkoe](https://avatars.discourse-cdn.com/v4/letter/s/919ad9/32.png) [@solkoe](https://boards.straightdope.com/u/solkoe)\ **Post date:** [February 26, 2008, 7:53pm UTC](https://boards.straightdope.com/t/couild-a-large-diamond-be-made-from-many-smaller-ones/439264/5 "2008-02-26T19:53:12Z")
[QUOTE=Squink] According to this [phase diagram for carbon](http://members.tm.net/lapointe/Carbon_Phase_Diagram.gif), you’ll need to melt your diamonds at 1000°C and 5,000,000 psi to favor diamond formation over graphite formation. [/QUOTE] Is this possible? ---
**Author:** ![The\_Controvert](https://avatars.discourse-cdn.com/v4/letter/t/dec6dc/32.png) [@The\_Controvert](https://boards.straightdope.com/u/The_Controvert)\ **Post date:** [February 26, 2008, 7:54pm UTC](https://boards.straightdope.com/t/couild-a-large-diamond-be-made-from-many-smaller-ones/439264/6 "2008-02-26T19:54:58Z")
Why not feed it cheap graphite instead of expensive diamonds then? ---
**Author:** ![Lemur866](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lemur866/32/434_2.png) [@Lemur866](https://boards.straightdope.com/u/Lemur866)\ **Post date:** [February 26, 2008, 8:06pm UTC](https://boards.straightdope.com/t/couild-a-large-diamond-be-made-from-many-smaller-ones/439264/7 "2008-02-26T20:06:54Z")
[QUOTE=solkoe] Is this possible? [/QUOTE] Of course it’s possible, we can make synthetic diamonds in the lab today. But there’s no sense in using geologically created diamonds as the feedstock for synthetic diamonds because it doesn’t matter what source the carbon comes from, and there are lots of cheaper pure carbon sources than diamond. > **[Synthetic diamond](https://en.wikipedia.org/wiki/Synthetic_diamond)** > > A synthetic diamond or laboratory-grown diamond (LGD), also called a lab-grown, laboratory-created, man-made, artisan-created, artificial, or cultured diamond, is a diamond that is produced in a controlled technological process, in contrast to a naturally formed diamond, which is created through geological processes and obtained by mining. Unlike diamond simulants (imitations of diamond made of superficially similar non-diamond materials), synthetic diamonds are composed of the same material ... ---
**Author:** ![Squink](https://avatars.discourse-cdn.com/v4/letter/s/b5e925/32.png) [@Squink](https://boards.straightdope.com/u/Squink)\ **Post date:** [February 26, 2008, 8:11pm UTC](https://boards.straightdope.com/t/couild-a-large-diamond-be-made-from-many-smaller-ones/439264/8 "2008-02-26T20:11:11Z")
[QUOTE=solkoe] Is this possible? [/QUOTE] Oops, I read the graph wrong. Diamond becomes the more stable form above a few _tens_ of atmospheres. [Gemesis](http://en.wikipedia.org/wiki/Gemesis) grows diamond crystals at 850psi and 1600°C, but they start with carbon. Starting with diamond might speed things up a bit, but that’s about it. -[Gemesis](http://www.gemesis.com/default.aspx) website with pictures of diamonds and slinky music. ---
**Author:** ![CalMeacham](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/calmeacham/32/35_2.png) [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)\ **Post date:** [February 26, 2008, 8:15pm UTC](https://boards.straightdope.com/t/couild-a-large-diamond-be-made-from-many-smaller-ones/439264/9 "2008-02-26T20:15:46Z")
> [@](#): > > You should be able to do it without heat and pressure. > Just do the same thing as if you were plating a bumper with chrome. > Put diamond salts into a bath, apply one wire to the crystal and turn on the juice. > The crystal will grow like sugar crystals in rock candy. Alas, that only works if the crystal structure is a stable one under the growing conditions, and it it’s thermodynamically possible to “plate out” atoms from solution onto your seed crystal. Since no one’s grown diamonds this way, you can bet that it’s not. Besides, you need something your “diamond salts” – that’s pure carbon – is going to dissolve in. The chemical vapor deposition method described in the wiki article is essentially a way to do this, but with vapor instead of a liquid solution. Still not easy, or it would not have needed such a long period of development. Besides, from my experience with crystal growth, I can say that you’d better have a REALLY clean seed crystal, or else you’ll end up with those parasitic non-aligned crystals sticking to your big one. So make sure all the little bits of crystal are COMPLETELY cleaned away (with growing from melt, you typically do this by melting off any tiny bits in the melt. They’re smaller than the seed, so they melt off first).