When I first started working on an outline for what would become this article, I thought it might be, in part, about whether we’d reached a point where lab-grown diamonds could be taken seriously as real diamonds. As far as I can tell, that debate is over. The Gemological Institute of America (GIA) says that lab-grown diamonds “have essentially the same chemical composition, crystal structure, optical, and physical properties of diamonds found in nature”.

If you’re buying a natural diamond at this point, you want the story that comes with it—the story that goes, “This gemstone came to be as the result of natural processes; people dug it out of the ground and now you’re wearing it.” And you’re paying a significant premium for that story. Looking at Blue Nile for pricing on comparable loose round diamonds:

I remember a time when a 5-carat diamond engagement ring signaled “my fiancé(e) is a professional athlete or their company just went public”. No longer.

To date, the story that people have gotten with a lab-grown diamond—not the price, but the story that comes with it—has generally been, “You can feel good about the ethics of what you’re buying.” And that’s both important and fair, because lab-grown diamonds eliminate the mining stage, and with it many of the environmental, geopolitical and worker-safety risks specific to extraction. (Note, though, that eliminating the mining stage doesn’t make the entire supply chain automatically ethical: energy sourcing, working conditions, cutting, and polishing still matter.)

But what if the story with a lab-grown diamond could be something more? What if your lab-grown diamond could be not only more ethically comfortable but also more sustainable?

First, a word about terminology. Depending on which company makes the lab-grown diamond, you’ll encounter different terminology used to describe its climate impact:

With those definitions in mind, how do lab-grown diamond makers go about achieving one of these definitions of sustainability? There are various paths, and they’re not mutually exclusive.

Diamond Foundry operates its Wenatchee, Washington foundry on hydropower and describes its facilities as having a “real-zero carbon footprint”. Its newer Spanish operations use solar and solar plus wind power. Diamond Foundry/VRAI, its jewelry brand, says that its Wenatchee diamond production uses Columbia River hydropower; its production is zero-emission; it has held CarbonNeutral certification since 2017; and following productions, its diamonds are cut and polished using a controlled supply chain.

Diamond Foundry’s approach is the most direct of the three: attack a major source of emissions before offsets or carbon accounting enter the picture. Diamond growth consumes large amounts of electricity, so power the foundry with low-carbon electricity.

What if a company could certify that an individual diamond was made to a low-carbon standard like that? And if that certification were an industry standard?

In 2024, ALTR became the first lab-grown diamond producer to receive a perfect 100 Sustainability Rating under the certification system SCS-007. SCS Global Services, originally Scientific Certification Systems, reported that ALTR recorded the lowest emissions in the program and was the second company certified for production powered by 100% renewable electricity. Certification included compliance with the standard’s net-zero-carbon-footprint requirements.

SCS-007 attempted something ambitious: origin traceability, ethical stewardship, sustainable production, climate responsibility, annual third-party audits, and additional requirements. Unfortunately, SCS-007 was recently retired. SCS said that the standard—which was a voluntary industry-led initiative—didn’t achieve the scale it needed, because mining operators didn’t adopt it and because chain-of-custody regulation remained a problem.

What this means is that the technology to make diamonds may be developing faster than the industry’s ability to create a common architecture of trust. SCS-007 showed that rigorous product-level assurance was possible; its failure to achieve scale shows how far the market remains from having a universally understood way to prove these claims.

At the same time, there are lab-grown diamond producers who go beyond climate neutrality and say that manufacturing a diamond can actually leave the atmosphere better off.

Some lab-grown diamond firms are going even farther and literally taking CO₂ that we don’t want in the atmosphere and converting it to feedstock for their production. It’s taking GHGs and making them into diamonds.

The UK firm Skydiamond uses captured atmospheric CO₂ as the carbon feedstock for its growth operation. It uses wind and solar power to produce diamonds at its facility in Gloucestershire, with the stones subsequently cut and polished in India. It says that an Imperial College London lifecycle analysis found the process carbon-negative and reports a 99.79% reduction in GHG emissions compared with mined diamonds. It also says that it doesn’t use offsets.

Similarly, Aether Diamonds starts with captured atmospheric CO₂, synthesizes a feedstock from the CO₂, and powers its growth operation with what it describes as 100 percent clean energy. However, Aether also says it does use carbon offsets for residual impacts, so it achieves what it claims as carbon negativity through clean energy plus offsets.

There’s an important point to be made here. The idea of making diamonds from carbon removed from the atmosphere is attractive, to be sure. But a diamond doesn’t contain very much carbon. One carat weighs 0.2 grams, and because diamond is essentially pure carbon, a one-carat stone contains only 0.2 grams of carbon, or the equivalent of 0.73 grams of atmospheric CO₂. To put that in perspective, an average gasoline car emits about that much CO₂ while traveling about 10 feet (3 meters).

In other words, removing carbon from the atmosphere to make the diamonds themselves is nice as far as it goes, but it’s not going to make a meaningful difference. The real different is in everything around that process: how the energy to power the foundry is produced, how much carbon the manufacturing avoids releasing, and how any remaining emissions are handled.

In researching this article, what I realized is that the answer to the question of whether a lab-grown diamond—or anything else, for that matter—is truly sustainable depends on where you draw the boundaries. And boundaries are complicated. For example, as described above, Diamond Foundry/VRAI describes a “real-zero carbon footprint”. The question is, what is the boundary to which that description applies? These are difficult questions and it’s not always possible to say what the right answer is:

…and so on. And that list of questions could easily be much longer. It’s all so complex that no consumer can be expected to keep track of it all. But in the end, I don’t think we have to.

The lesson here isn’t that any lab-grown diamond is inherently sustainable. It isn’t. Lab-grown tells you how the crystal originated, not what powered the reactor, where it was cut, or what happened to the remaining emissions.

But a new approach is possible. Today, we can buy a diamond whose producer can tell us where its electricity came from, account for its emissions, disclose the boundary of that accounting, and—in the strongest cases—have someone independent check their work.

Whether any particular diamond is truly zero-emission, carbon neutral, net zero, or carbon negative may still depend on where the boundaries are drawn. But now, instead of asking whether a lower-carbon diamond is theoretically possible, we can ask whether a particular diamond producer can prove it.

That seems like a much more interesting story.