Diamonds Aren't Formed from Coal. Here's How It Actually Happens

couple holding hands on table

If you're a completist shopper like us, you always want to know where your products originate. You may know that With Clarity diamonds are ethically sourced and mined, but have you ever wondered where diamonds come from, period? As in, how are diamonds formed? What magic dust and dinosaur breath combined a million years ago to create the foundation of the modern engagement ring? Read on for a brief history — and future view — of diamond formation, and some fascinating facts about diamond strength and structure.

Are diamonds made from coal?

So diamonds were once pieces of coal that have been transformed under high pressure and temperature, right? Nope! This is an old wives' tale, just like "another drink will cure your hangover" or the idea that being out in the cold causes you to catch a cold. Diamonds are actually much older than plants, which are the main ingredient for the formation of coal.

The basic old-fashioned recipe for a diamond: Carbon deposits, deep within the earth, that are subjected to temperature and pressure.

The exact time that it takes for a diamond to form within the earth is unknown. Some materialize in days, weeks or months. Others take millions of years. Most diamonds are hundreds of millions of years old, with many dating back 1 to 3 billion years. That's because diamond growth isn’t always a continuous process. A diamond might start to grow, then experience an interruption because of a change in temperature or pressure. It could sit for hundreds or millions of years before growth resumes.

How old are diamonds? A diamond can’t be dated to find out its precise age, but inclusions of other minerals can suggest an estimate. Diamond inclusions that contain specific elements like potassium can be subjected to radioactive dating.

As the diamonds form deep in the earth, they withstand exposure to all sorts of gasses, minerals, and other materials surrounding the ore. Although the budding gem hardens to an unbreakable state, anything it touches during this phase can impact its color. Most diamonds appear white, but upon further inspection, have a yellowish tint or a light, almost imperceptible shade of brown. This doesn't mean that there is anything "wrong" with the diamonds, just that they're unique in their beauty.

How are diamonds formed?

So how do diamonds form? There are four main ways. We'll break them all down below, but you can also use the image just below this paragraph for an illustration of each point.

four zones of diamond formation


Most diamonds are found in commercial mines, but they were actually formed inside the Earth’s mantle, about 150 kilometers below the Earth's crust. Diamonds are created in something called a "diamond stability zone" in the upper mantle, a high-pressure region that has a temperature of over 1,000 degrees Celsius. Diamonds are continually forming and growing there, just as they have been for billions of years. The gems are brought to the surface of the Earth during a seismic event like a volcanic eruption, embedded in large chunks of rocks called xenoliths.


Diamonds are also thought to form in "subduction zones," a.k.a. places where the tectonic plates that are constantly, gradually moving beneath the earth's surface come together, causing one plate to move underneath the other. Some studies suggest that subducted seawater is involved in the formation of diamonds in these zones; others have found these diamonds contain tiny bits of oceanic crust.


Intriguingly, some diamonds are believed to result from asteroid strikes. Whenever an asteroid hits the earth's surface, extremely high temperature and pressure are produced. Diamonds have been found in meteor craters in Arizona and Siberia, Russia, where excavators at the Popigai Crater have come across diamonds up to 13 millimeters in size.


Talk about space rocks. Researchers at NASA have found extremely small pieces of diamonds in extraterrestrial bodies. These have formed either in outer space or in the mantle of other planets.

Diamond chemical structure and strength of diamonds

The chemical formula of a diamond is C, the same as the MVP of all elements, carbon. However, graphite and soot are also made of pure carbon atoms. So how do you differentiate between soot, graphite, and diamond? It has to do with the chemical structure of a diamond.

Carbon atoms can be arranged in many different physical forms, which are called allotropes. In a diamond, the carbon atoms are all covalently bonded to one another. They produce a three-dimensional network solid, a strong allotrope that differs from those of graphite and soot, which are more relatable to chicken wire.

How strong are diamonds compared to other gems? As the most concentrated form of pure carbon in the natural world, diamonds are the strongest mineral known on earth. They sit at the top of the Mohs hardness scale, which measures the ability of one mineral to scratch another visibly.

Lab-made diamonds

Technology marches on, even when it comes to diamonds. Diamonds now can be made in a lab, and they're growing in popularity. Lab-grown diamonds will have the same look and feel of a natural diamond because the growing process recreates the carbon-atom structures formed by Mother Nature.

When growing diamonds in a lab, technicians place acid into a heat and pressure chamber, replicating the natural growth process. The diamond crystallizes and matures within six to 10 weeks. The diamond is then polished and graded.

Lab-made diamonds are often called "synthetic," but that doesn't mean they're fake. They're identical to diamonds that are mined; they just didn't come from the earth. In fact, if you use any of the tests to find out if a diamond is real, a lab-made diamond will pass. Because it is a diamond.

Are Lab Created Diamonds Synthetic?

No! This is one of the most common misconceptions, and one of the biggest. Many people consistently associate the term “lab created” with “fake.” This is not always the case. While some diamonds and gemstones created in labs ARE synthetic (that is the only way to create those kinds of gemstones, after all), not every lab created diamond is a fake one. We know how confusing this can be. After all, it does sound as though something created in some laboratory cannot possibly be the same as what one would find in nature. To fully understand, you must first know the difference between synthetic diamonds and the lab created real diamonds.

Synthetic Diamonds

Synthetic diamonds are exactly how they sound: they are essentially replicas of real diamonds. This category of gemstone includes the zirconia, moissanite, and many others. Some of them appear to have the same, or similar, qualities as real diamonds, but the differences can almost always be detected by the naked eye. Moreover, they are made during a process that takes place in a lab, and every element of creation is carefully observed and controlled.

Shop Moissanite Rings

Real Lab Created Diamonds

Yes, we know. Sounds like something of a paradox, right? After all, synthetic diamonds like the cubic zirconia are created in labs. So, how is it that authentic diamonds could come from a lab? It’s simple. Well, the process itself is far from simple, but it can be (fairly) easily explained.

Authentic lab created diamonds are made from pieces of ACTUAL diamond (sometimes called seeds). While some types of synthetic gemstones are made in a similar fashion, the authentic lab created diamonds undergo a process that mimics what happens during natural, in-ground diamond formation identically. Well, almost identically.

To produce a higher number of diamonds in a shorter amount of time, this replicated process is designed to progress much faster than diamond formation would be able to in nature. Also, unlike the diamonds forming naturally, lab created diamonds are closely monitored by teams of experts, to ensure that the process is occurring as it should and that the quality and integrity of the lab grown diamonds remain intact.

Shop Lab Diamonds

Can You Tell the Difference Just by Looking at the Diamonds?

Often, yes. As we mentioned above, it is usually easy to identify the differences between synthetic and real diamonds just by looking at the gemstone. The clarity will often be nothing like that of a real diamond, and they can sometimes be easily damaged, whereas authentic diamonds cannot. Also, in many cases, synthetic diamonds are too flawless. That may sound strange, but it’s true.

The reason is that, since synthetic diamonds do not undergo the same process of formation (the process replicated for the growth and formation of lab created diamonds), they do not end up with all the inclusions that naturally mined or lab created diamonds do. Therefore, when they are completed, they are essentially flawless, unlike our beloved authentic diamonds.

The same can also apply to the color of the diamond, as well as some of its other qualities. If, however, you are attempting to compare diamonds for yourself and you are not sure what to look for, take your diamonds to a specialist!

Does This Mean that One Kind is Better?

No! Beauty is in the eye of the beholder, and so is the idea of one diamond being “better” than another. The quality of your diamond depends solely on the way it formed as it developed, even if it is a synthetic one.

Another of the big misconceptions people discuss today is that synthetic diamonds equal cheap or lesser. However, all it really means is that they are made a bit differently than naturally mined or lab created diamonds. So, deciding on which kind of diamond is better for you really depends more on your budget and personal taste.

A lab grown diamond’s price may be higher than that of synthetic diamonds, or you may simply like the absolutely perfect appearance of synthetic diamonds. That decision is really entirely up to you!

Still interested in a diamond but don’t know where to start?

We’ll have our experts search for three personalized diamond suggestions that fit your tastes and budget. Like one? Wonderful! We can chat from there. None of them fit? Tell us. Our experts want you to be happy, and they’ll go back to the drawing board to find that perfect fit.

Fill out my online form.