# Limit to the size of a diamond? **URL:** \ **Category:** Factual Questions\ **Created:** [February 15, 2005, 2:38pm UTC](https://boards.straightdope.com/t/limit-to-the-size-of-a-diamond/290192 "2005-02-15T14:38:31Z")\ **Posts on this page:** 13\ **Page:** 1
**Author:** ![Khadaji](https://avatars.discourse-cdn.com/v4/letter/k/9e8a1a/32.png) [@Khadaji](https://boards.straightdope.com/u/Khadaji)\ **Post date:** [February 15, 2005, 2:38pm UTC](https://boards.straightdope.com/t/limit-to-the-size-of-a-diamond/290192/1 "2005-02-15T14:38:31Z")
While reading a SciFi short the author descirbed a moon-sized diamond. I was wondering, is there any restriction on how large a diamond could be? ---
**Author:** ![mks57](https://avatars.discourse-cdn.com/v4/letter/m/b9bd4f/32.png) [@mks57](https://boards.straightdope.com/u/mks57)\ **Post date:** [February 15, 2005, 2:43pm UTC](https://boards.straightdope.com/t/limit-to-the-size-of-a-diamond/290192/2 "2005-02-15T14:43:18Z")
> [@Khadaji](#): > > While reading a SciFi short the author descirbed a moon-sized diamond. I was wondering, is there any restriction on how large a diamond could be? Depending on the circumstances, at some size it would just collapse into a neutron star. ---
**Author:** ![chrisk](https://avatars.discourse-cdn.com/v4/letter/c/6de8d8/32.png) [@chrisk](https://boards.straightdope.com/u/chrisk)\ **Post date:** [February 15, 2005, 2:57pm UTC](https://boards.straightdope.com/t/limit-to-the-size-of-a-diamond/290192/3 "2005-02-15T14:57:33Z")
> [@mks57](#): > > Depending on the circumstances, at some size it would just collapse into a neutron star. Hmmm… okay, let’s see. At some point _before_ that, I presume that gravitational force would be strong enough to induce carbon fusion at the heart of the diamond… making it a ‘carbon star’ of a type that AFAIK has not been observed. Somebody else can probably beat that though. Next? 😃 ---
**Author:** ![flight](https://avatars.discourse-cdn.com/v4/letter/f/bbce88/32.png) [@flight](https://boards.straightdope.com/u/flight)\ **Post date:** [February 15, 2005, 2:59pm UTC](https://boards.straightdope.com/t/limit-to-the-size-of-a-diamond/290192/4 "2005-02-15T14:59:33Z")
Yeah, but it’s probably an I3, I always think it’s tacky to go for the moon-sized diamonds with obvious flaws over the flawless mountain sized diamonds. ---
**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:** [February 15, 2005, 3:20pm UTC](https://boards.straightdope.com/t/limit-to-the-size-of-a-diamond/290192/5 "2005-02-15T15:20:16Z")
In order to _form_ a diamond, you have to put a load of carbon together, then subject it to temperature and pressure\*, which means that your diamond must start off as part of a larger mass; this larger mass would obviously mean that only a _portion_ of your absolute mass limit (before fusion occurs) is going to end up as diamond. \*Actually not necessarily true; diamonds can be ‘grown’ by vapour deposition, but I think it would take quite an exotic set of circumstances for anything sizeable, pure and single-crystal to naturally form that way. ---
**Author:** ![bluecanary](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bluecanary/32/3614_2.png) [@bluecanary](https://boards.straightdope.com/u/bluecanary)\ **Post date:** [February 15, 2005, 3:22pm UTC](https://boards.straightdope.com/t/limit-to-the-size-of-a-diamond/290192/6 "2005-02-15T15:22:08Z")
Wasn’t there a diamond star discovered (and called ‘Lucy’ after the song)? ---
**Author:** ![MikeS](https://avatars.discourse-cdn.com/v4/letter/m/919ad9/32.png) [@MikeS](https://boards.straightdope.com/u/MikeS)\ **Post date:** [February 15, 2005, 3:52pm UTC](https://boards.straightdope.com/t/limit-to-the-size-of-a-diamond/290192/7 "2005-02-15T15:52:56Z")
> [@bluecanary](#): > > Wasn’t there a diamond star discovered (and called ‘Lucy’ after the song)? I honestly thought you were thinking of _2010_, by Arthur C. Clarke, when I first read this… but [you’re right.](http://news.bbc.co.uk/1/hi/sci/tech/3492919.stm) ---
**Author:** ![mks57](https://avatars.discourse-cdn.com/v4/letter/m/b9bd4f/32.png) [@mks57](https://boards.straightdope.com/u/mks57)\ **Post date:** [February 15, 2005, 4:04pm UTC](https://boards.straightdope.com/t/limit-to-the-size-of-a-diamond/290192/8 "2005-02-15T16:04:24Z")
> [@chrisk](#): > > Hmmm… okay, let’s see. At some point _before_ that, I presume that gravitational force would be strong enough to induce carbon fusion at the heart of the diamond… making it a ‘carbon star’ of a type that AFAIK has not been observed. Somebody else can probably beat that though. > > Next? 😃 I thought of carbon fusion, but I thought that it could be avoided if the temperature of the diamond was kept low. Pressure alone should not induce fusion. ---
**Author:** ![F.U.Shakespeare](https://avatars.discourse-cdn.com/v4/letter/f/aca169/32.png) [@F.U.Shakespeare](https://boards.straightdope.com/u/F.U.Shakespeare)\ **Post date:** [February 15, 2005, 4:24pm UTC](https://boards.straightdope.com/t/limit-to-the-size-of-a-diamond/290192/9 "2005-02-15T16:24:25Z")
_Lucy?_ C’mon, a diamond that big should be named after Fran Drescher, or maybe Liberace. > [@MikeS](#): > > I honestly thought you were thinking of _2010_, by Arthur C. Clarke, when I first read this… but [you’re right.](http://news.bbc.co.uk/1/hi/sci/tech/3492919.stm) ---
**Author:** ![Fuji\_Kitakyusho](https://avatars.discourse-cdn.com/v4/letter/f/f0a364/32.png) [@Fuji\_Kitakyusho](https://boards.straightdope.com/u/Fuji_Kitakyusho)\ **Post date:** [February 15, 2005, 6:31pm UTC](https://boards.straightdope.com/t/limit-to-the-size-of-a-diamond/290192/10 "2005-02-15T18:31:27Z")
For those of us who simply can’t afford a star sized diamond, what is the largest chuck of cubic zirconium in the universe? ---
**Author:** ![Finagle](https://avatars.discourse-cdn.com/v4/letter/f/b19c9b/32.png) [@Finagle](https://boards.straightdope.com/u/Finagle)\ **Post date:** [February 15, 2005, 7:00pm UTC](https://boards.straightdope.com/t/limit-to-the-size-of-a-diamond/290192/11 "2005-02-15T19:00:18Z")
> [@Khadaji](#): > > While reading a SciFi short the author descirbed a moon-sized diamond. I was wondering, is there any restriction on how large a diamond could be? Well, at some point, gravitational forces are going to cause the crystalline structure to shear. So I don’t think you’d have a single moon-sized crystal, but rather a moon-sized ball of diamond crystals, some of which are very large. Still, looking at [this](http://www.zyvex.com/nanotech/talks/NCSU980206/sld023.htm), diamond has a pretty high compressive strength. Something like 5,000,000 kg/cubic centimeter. With a density of 3.51 g/cc, then on Earth, it seems as though you could build a diamond pillar something like 14,000km high (in the unlikely case I haven’t screwed up the math). So based just on compressive strength (and ignoring all the material science issues of which I’m totally ignorant), it looks like an Earth-sized ball of diamond isn’t out of the question. But realistically, that’s going to more than a couple of month’s salary. ---
**Author:** ![Squink](https://avatars.discourse-cdn.com/v4/letter/s/b5e925/32.png) [@Squink](https://boards.straightdope.com/u/Squink)\ **Post date:** [February 15, 2005, 7:08pm UTC](https://boards.straightdope.com/t/limit-to-the-size-of-a-diamond/290192/12 "2005-02-15T19:08:50Z")
[Diamond Planets](http://www.space.com/scienceastronomy/diamond_planets_050208.html) ---
**Author:** ![smiling\_bandit](https://avatars.discourse-cdn.com/v4/letter/s/e9a140/32.png) [@smiling\_bandit](https://boards.straightdope.com/u/smiling_bandit)\ **Post date:** [February 15, 2005, 8:49pm UTC](https://boards.straightdope.com/t/limit-to-the-size-of-a-diamond/290192/13 "2005-02-15T20:49:48Z")
> [@](#): > > The diamond star completely outclasses the largest diamond on Earth, the 530-carat Star of Africa which resides in the British Crown Jewels 🆒 Somehow, I don’t think the British royal family is worried about their crown jewels depreciating any time soon.