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I was having a discussion with my friend about the intrinsic worthlessness of diamonds (DeBeers and whatnot) and how synthetic diamonds haven't caught on, again because of the marketing/propoganda that natural diamonds are "better". My friend, partially to spite me because he doesn't like to lose an argument, claims that synthetic diamonds have only been produced with a hardness up to 9.8, and you can only get a hardness of 10 with a natural diamond.

I call BS on that. A little research indicates that while natural diamonds may slightly vary in hardness (the impurities which alter the color also modify its crystal properties), synthetic diamonds have a more consistent hardness which is otherwise identical to a naturally-occurring diamond with the same chemical properties. This appears to make sense.

Are chemically-identical synthetic and natural diamonds of equivalent hardness? Or is there a caveat to the synthetic diamond-making process that produces weaker diamonds?

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  • $\begingroup$ I should (guessing here) think synthetic ones would tend to be harder than the natural ones: let's say that they are CVD made ones, then one can control the crystal growth very precisely and so the product on the whole would have fewer flaws. The natural ones' hardnesses vary because the frequency of flaws and disruptions in the crystal varies. Check out these beautiful synthetic diamond waveguides opticsinfobase.org/oe/abstract.cfm?uri=oe-16-24-19512 $\endgroup$
    – Selene Routley
    Commented Nov 29, 2013 at 5:09
  • $\begingroup$ hardness is a function of purity and crystal uniformity so synthetics softer than naturals must be pioneer synthetics (the early manmade diamonds). otherwise in today's tech there is no scientific reason for saying natural diamonds are in any way superior to synthetic ones. in fact the opposite is true. telegraph.co.uk/news/worldnews/asia/japan/8213452/… $\endgroup$
    – gregsan
    Commented Nov 29, 2013 at 8:01

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The laboratory made diamonds are as good as the naturally found ones. It is the same crystal structure. They are not used much as gemstones, (2% of the market) because of the objections of the diamond industry which relies on mined diamonds and dominates the markets.

Gem-quality diamonds grown in a lab can be chemically, physically and optically identical (and sometimes superior) to naturally occurring ones. The mined diamond industry has undertaken legal, marketing and distribution countermeasures to protect its market from the emerging presence of synthetic diamonds. Man-made diamonds can be distinguished by spectroscopy in the infrared, ultraviolet, or X-ray wavelengths. The DiamondView tester from De Beers uses UV fluorescence to detect trace impurities of nitrogen, nickel or other metals in HPHT or CVD diamonds.[

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    $\begingroup$ Do yo have a source for that quote? $\endgroup$
    – user288447
    Commented Feb 13, 2014 at 10:47
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    $\begingroup$ @user288447 it is from the link given in the first paragraph $\endgroup$
    – anna v
    Commented Feb 13, 2014 at 11:35
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Natural diamonds are slightly harder than synthetic diamonds. This is very commonly known in manufacturing (diamond-tipped drills etc) and there is plenty of engineering resources on the subject. However for jewelry purposes, a trained jeweler can almost never pick out a real vs synthetic without special tools for that purpose.

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    $\begingroup$ How do you reconcile this with, for instance, this: en.wikipedia.org/wiki/Synthetic_diamond#Hardness? Here, it is asserted (with references) that synthetic diamonds harder than any natural one can be produced using chemical vapor deposition $\endgroup$
    – Danu
    Commented Feb 13, 2014 at 0:18
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    $\begingroup$ I'd really like an explanation, like @Danu . There is the following simple logic: under controlled conditions one can ensure that the perfectly periodic tetrahedral structure is realised, whereas natural diamonds have inclusions in them and flaws. It may well be that some natural diamonds could be harder owing to certain kinds of covalent bonds being formed with substances other than carbon, but it would have to be a fairly "systematic" "brewing" of the right mixtures, so one would have to account for what gives rise to these conditions.See also physics.stackexchange.com/a/88306/26076 $\endgroup$
    – Selene Routley
    Commented Feb 13, 2014 at 0:48

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