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I have constantly been told through my K-12 Education that diamonds are a product of carbon, time, pressure, and temperature. If this is true, what is stopping someone from building a high-pressure, high-temperature system and dumping graphite in and making millions of diamonds?

It seems my exact strategy is listed here: https://en.wikipedia.org/wiki/Synthetic_diamond#High_pressure.2C_high_temperature . But this is under the article "synthetic diamond." How can one tell a difference between a synthetic diamond and a "real" diamond? What is stopping someone from making these HPHT machines and making tons of money?

Update: I watched the BBC special on synthetic diamonds (https://www.youtube.com/watch?v=5d2WebdMpBQ) and De Beers shows you can tell the difference between synthetic and real diamonds by their reaction to UV radiation. I am still interested in how I can make a DIY diamond if anyone has details on that. And to make this more on topic, how best I can simulate the Earth's formation of diamond? Why is the Earth's formation of diamond different from these HPHT and CVD diamonds?

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    $\begingroup$ You are describing the synthetic diamond industry. This is the business model of Gemesis and Scio Diamond, among others. They use HPHT and chemical vapour deposition or CVD (as you mention). I think you should continue your research a bit and edit your question to something a little more pointed. $\endgroup$ – kwinkunks May 9 '16 at 11:34
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    $\begingroup$ I can't answer why synthetic diamonds are different from natural ones (I reject the use of "real" for only one of these), although I'm sure people have studied it. I will note, however, that De Beers' entire market would vanish if people stopped valuing natural ones more - so they may not be the best source of information on the topic :-) $\endgroup$ – Semidiurnal Simon May 9 '16 at 11:45
  • $\begingroup$ Your question has its own answer - time. It takes time to crystallize a reasonable sized diamond. And have you any idea how difficult it is to generate the requisite pressure of > 10GPa? $\endgroup$ – Gordon Stanger May 9 '16 at 13:01
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what is stopping someone from building a high-pressure, high-temperature system and dumping graphite in and making millions of diamonds?

What is stopping someone from making these HPHT machines and making tons of money?

No one, and it is done. First of all, synthetic diamonds have been out on the market for quite some time now and it's a well established business. You've heard of diamond saws, diamond drills, diamond polishing paste and all kinds of other diamond products. So people make them, sell them, and make money.

It's not even that hard: In our own lab we got a machine that can make diamonds (among other HPHT) stuff. Someone once even put some peanut butter and made diamonds out of it (micrometre sized, though). Here's a picture of the machine (called a piston cylinder): enter image description here

Here's a picture of how this might look:

enter image description here

Note that this one is not from our lab, but it's a really nice picture of how this stuff looks when you make it in such machines. This one's from this paper. The diamond crystals are about 30 μm across. Not something you'd put on a ring.

The big question is how do you make gemstone quality diamonds. Chemical vapour deposition seems like the most successful method. There are other methods, but it's pretty easy to distinguish them from natural diamonds (example). It is still quite hard to do it: it's not something anyone can just do in their backyard. With technology it becomes easier though. Here comes the question of regulation. Gemesis, one of the companies that makes them, engraves a serial number using laser on each synthetic gem-quality diamond they make. But what about some evil diamond makers who want to simulate natural stones? As with any other synthetic material, there are imperfections that are different from imperfections found in natural stones. Moreover, each mine or region where diamonds come from has a different fingerprint (they use that to trace blood diamonds). There are methods to analyse the diamonds to detect this. UV and IR spectroscopy, laser ablation, isotope analysis, cathodoluminescence and others. Some are easier and cheaper than others.

So you can't just make up impurities to say "look it's natural", they have to be consistent with a specific diamond source you're trying to imitate. And that's - not very easy. Likely impossible with today's technology.

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  • $\begingroup$ This fine answer could use some references or at least a couple more links. $\endgroup$ – kwinkunks May 10 '16 at 9:54
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    $\begingroup$ @kwinkunks done. Also some pictures because why not $\endgroup$ – Gimelist May 10 '16 at 9:59
  • $\begingroup$ great answer @Michael Where do I get a machine like the one in your lab? How fast does it make diamonds? $\endgroup$ – Seth Kitchen May 10 '16 at 15:53
  • $\begingroup$ @SethKitchen you don't. It was designed for scientific research, not for the commercial production of diamonds. It could cost tens to hundreds of thousands of dollars to build and operate and you would make just a handful of micro diamonds of no commercial value. You better get a CVD instead. $\endgroup$ – Gimelist May 10 '16 at 19:05

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