Lab-Grown Diamonds – HPHT – CVD

Now that the poolside grill-fest that is Memorial Day is behind us, it’s time for a pop quiz to jolt us out of our carb-induced somnolence. So here’s a question: what do semiconductors, LEDs, solar panels, and diamonds have in common? Take a moment, we’ll be right here waiting…

No, it’s not that they’re all expensive but more that they all share similar processes in terms of their creation. Wait a moment! Are we saying that volcanic processes are involved with all of these products? No! Read on and let’s dive into the sparkling world of laboratory synthesized gemstones…

With summer finally here (at least in the US), the month of June heralds one of the most romantic times of the year. Indeed, with Bridal Season now upon us, it is also the most expensive. For some. The reception venue, band, photographer, ceremony site, cake, favors…the list of serious expenses seems never-ending. Not to mention the stress of paperwork, travel woes, and where to seat that inevitable family member whose sorely outdated views on absolutely everything are guaranteed to alienate most of the guests. Admit it – there’s one in every family. And even before that there’s also the expense of the engagement ring. Back in the 1940s, De Beers, the world’s first and largest diamond cartel, launched its now iconic marketing campaign: A diamond is forever. Crafted by ad agency N. W. Ayers, based in Philadelphia, the campaign positioned the stone as the ultimate symbol of enduring commitment and everlasting love. And the reason for this marketing push was simple: once scarce, a huge seam of the rocks had been discovered in South Africa and access to diamonds was suddenly no longer restricted. With a potential glut on the market, steps had to be taken to prevent a price crash and thus the campaign was born. Combining the romance of eternal love with the ‘2 Months Rule’ (an engagement ring should cost the equivalent of two months’ salary), De Beers created a preeminent status symbol while also keeping prices – and their profits – high.

Fast forward to today and although the average engagement ring costs around $5,680 according to The Knot, ‘the nation’s leading wedding marketplace’, this level of expense is no longer strictly necessary.(1) Why? Because these days the thrifty romantic can opt not for a natural diamond but instead for a synthetic version grown in a lab. But how close are they to the ‘real thing?’ Good question – let’s take a look…

Naturally occurring around 100 miles below the Earth’s surface, diamonds result from the interaction of extreme pressure with high temperature and are brought to the surface in volcanic eruptions.

As far back as 1893 attempts to create a synthesized diamond were underway as Henri Moissan claimed success by heating charcoal to 3500 degrees Celsius in a carbon crucible.(2) However, according to Arden Jewelers, the jewelers behind the popular online resource MyGemologist.com, Moissan’s claim was never verified and the quest continued. In the middle of last century it became possible to generate small stones that were deployed in industrial processes such as those used in the electronics field. These synthesized rocks, however, had no value within the jewelry market given their diminutive size and dull brown color and, according to an article in the Robb Report, ‘it was not until earlier this decade that producers figured out how to consistently turn out large, colorless stones that could be used in jewelry.’(3) But since other precious and semi-precious stones such as rubies and emeralds were already being grown artificially, what was the difficulty with diamonds? Some of the problem lies in replicating the effects of the natural processes necessary in the gem’s formation. Naturally occurring around 100 miles below the Earth’s surface, diamonds result from the interaction of extreme pressure with high temperature and are brought to the surface in volcanic eruptions. As the molten magma ejected in a volcanic episode cools, it forms vertical tubes known as kimberlite pipes. Roughly one in every two hundred of these pipes actually contains rough diamonds and the challenge is both in identifying that percentage of tubes and in mining the diamonds therein.

So given that this natural process is somewhat challenging to recreate in a laboratory environment, how are synthetic diamonds produced?

The simple answer is that the technology has been steadily evolving and two main methods now exist for manufacturing the gem stones. The oldest of these is High Pressure/High Temperature (HPHT) manufacture wherein a diamond seed is nestled in carbon and one of three types of press is used to build up the seed. Whether using a split-sphere press, a cubic press, or a belt press, intense pressure of over 1.5 million pounds per square inch is generated and the seed is also subjected to temperatures above 2000 degrees Celsius. In this environment, carbon within the chamber melts and adheres to the seed, creating a small stone that can be used in industrial applications. But for high-quality, wearable stones, however, CVD – or Chemical Vapor Deposition – is the preferred method of manufacture. It works like this…

In the same way that a speck of sand is the basis for the pearl, so a tiny slice of a ‘seed’ diamond is the main building block in a synthesized diamond.

A more recent technique than HTHP,  Chemical Vapor Deposition is already used in the semiconductor manufacturing business to produce thin films. Due to its ability to deposit extremely thin layers of material – known as ‘atomic layer deposition’ – it is employed in the manufacture of integrated circuits, photovoltaic cells and devices, and some variations of the technique can be used to create graphene, a material we discussed in our July 2017 article ‘How 2D Graphene Exists in a 3D World: Cleanroom Technology Creates the Impossible.’ In creating diamonds, it follows a similar process to that of an oyster with its pearl. In the same way that a speck of sand is the basis for the pearl, so a tiny slice of a ‘seed’ diamond is the main building block in a synthesized diamond. Placed in a growth chamber, the seed is exposed to a ball of super-heated plasma composed of methane (a carbon-rich gas) and hydrogen. The gases are then ionized using lasers or microwaves to break apart their molecular bonds, allowing the pure carbon to adhere to the seed. The huge advantage of this method is that temperatures are lower – only around 800 degrees Celsius – and there is no longer a need for the intense pressures required by HPHT manufacturing. And CVD arguably works better: according to Arden Jeweler ‘CVD diamonds can be grown over larger areas by starting with a larger diamond seed plate. […And] the CVD process allows for a finer control over the environment in the growth chamber and thus the properties of the finished diamond.’(4)

However, that process is not wholly without flaws. Due to the etching of silica in the windows of the growth chambers, small silicon inclusions may appear in the finished stones. Inclusions – basically, flaws – exist in both synthesized and naturally occurring diamonds and, although usually not visible to the naked eye, do affect the value of the stone. On the other hand, the pitfalls of the HTHP process are rather evident: the accidental introduction of nitrogen, for example, will turn the growing stone yellow, and that of boron will result in an uncharacteristically blue gem – far from the colorless gems usually demanded.

However the potential for such problems does not seem to be stemming the demand for artificial diamonds. In fact, due to advances made in the manufacturing techniques, the Federal Trade Commission (FTC) now recognizes cultured stones as genuine diamonds and, moreover, no longer demands that lab-grown stones be labelled ‘synthetic.’ Of course, for some buyers, synthesized diamonds may seem to lack the romance of the natural stone. But in our world of increasingly conscientious consumerism it is also important to bear in mind that the advantages these lab-grown alternatives offer extend beyond mere price. Indeed fueling the already $280 million business is the fact that opting for lab-gown sparkle helps buyers to side-step ethically questionable issues such as the environmental impact of traditional mining on sensitive ecosystems.(5) And this is significant because the diamond mining industry has a long tradition of exploitation and destruction – read more in the excellent article by Michael Fried, ‘Ethical diamonds: What Conscientious Consumers Need to Know’ published by The Diamond Pro.(6)

Additionally by choosing lab-grown gems, buyers no longer need be concerned about the legitimacy of so-called ‘conflict-free’ diamonds. In contrast to their popular usage, within the diamond industry the terms ‘origin’ and ‘provenance’ are not interchangeable. ‘Provenance’ indicates the last location in the supply chain before the gem is sold to the consumer, whereas ‘origin’ denotes the country in which the stones are mined. This distinction has implications regarding the stone which may then be conflict-free by provenance but not by origin.

All of these issues are to be borne in mind when selecting a stone to accompany that ‘all important question’ and it is fortunate that the technology now exists to craft diamonds that, at least to the naked eye, are as close to nature-identical as it is possible to be.

And it is hard not to be impressed that the same technology used in the manufacture of purely industrial items such as solar panels, LEDs, and semiconductors, is also deployed in the creation of something so aesthetically pleasing, romantically charged, and eternally symbolic as a diamond.

After all, whether naturally-sourced or lab-grown, a diamond is forever…

Are you considering the pros and cons of a lab-grown stone for your significant other? Or perhaps you’d only ever consider a naturally occurring diamond? Let us know your thoughts!

References:

1. https://www.theknot.com/content/how-much-to-spend-on-engagement-ring
2. https://www.mygemologist.com/learn/lab-grown-diamonds/how-are-lab-grown-diamonds-made/
3. https://robbreport.com/style/jewelry/lab-grown-diamonds-moment-2851840/
4. https://www.mygemologist.com/learn/lab-grown-diamonds/how-are-lab-grown-diamonds-made/
5. https://robbreport.com/style/jewelry/lab-grown-diamonds-moment-2851840/
6. https://www.diamonds.pro/education/ethical-diamonds-conscientious-consumers-need-know/