How to Tell the Difference Between Lab-Grown and Mined Diamonds

Lab-grown diamonds (LGD) have been widely available to consumers since about the mid-2010s, and for a number of reasons, they are becoming a popular alternative to mined diamonds. Their lower price is certainly one reason for the interest in LGD, but it may also lead consumers to believe that LGD are of lower quality than mined diamonds. You’ll often read that both mined and lab-grown diamonds have the same chemical composition and optical properties, but what exactly does that mean? Let’s talk about the differences and similarities between mined and lab-grown diamonds (and there are far more similarities!), and how one could go about telling one from the other.

What Is a Diamond?

The definition of “diamond,” according to the Federal Trade Commission, is “a mineral consisting essentially of pure carbon crystallized in the isometric system.” So while for commercial purposes anyone selling a diamond must clarify whether the diamond came out of the ground or a laboratory, the two types of diamond are essentially chemically identical. The two instances of “essentially” in this paragraph might seem like a weasel word concealing vast differences, but when the FTC says a diamond is ”essentially” pure carbon, they mean that a diamond is about 99.95% carbon. Trace elements and other compounds that get trapped inside the crystal during growth comprise the other 0.05%. This is true of both mined and lab-grown diamonds, and in many cases, lab-grown diamonds are more pure than mined diamonds.

Trace Elements and Inclusions

The trace elements found in diamonds are typically nitrogen and boron because of the ease with which these elements bond with carbon. Nitrogen can give a diamond a yellow tint, while boron turns a diamond blue. Mined diamonds contain more nitrogen than lab-grown diamonds, but since lab-grown diamonds can also be yellow (or any other color that diamonds can be), one cannot conclude that a diamond is a mined diamond just by looking at its color.

Both mined and lab-grown diamonds contain inclusions. An inclusion is any material trapped inside the mineral during growth, usually tiny pockets or bubbles of gas or liquid, though it’s not uncommon to find other minerals or crystals trapped within another mineral. Since lab-grown diamonds are grown in a molten metal solution, lab-grown diamonds tend to have more metallic inclusions, though the presence of metallic inclusions is not exclusive to lab-grown diamonds. Part of the art of growing diamonds involves reducing inclusions, as they can diminish the clarity of the diamond.

Fluorescence

When exposed to ultraviolet (UV light), about 35% of mined diamonds exhibit a phenomenon called fluorescence. Colorless lab-grown diamonds never exhibit fluorescence, but fancy-color LGD do. So while not all diamonds exhibit fluorescence, a colorless diamond that does exhibit fluorescence is most likely a mined diamond.

Is fluorescence a desirable characteristic? Whether fluorescence adds to or detracts from a diamond’s appearance is up for debate. While blue fluorescence can cancel out a diamond’s yellow tint and make it appear colorless, strong fluorescence can make a diamond appear hazy, lowering its desirable clarity.

Growth Morphology

Every crystal exhibits a particular growth morphology depending on the type of crystal and the solution in which it grows. Both mined diamonds and lab-grown diamonds grown using the HTHP method, grow in a molten solution mostly composed of iron. For CVD lab-grown diamonds, the solution is a hydrocarbon gas.

The different solutions these different types of diamonds are grown in results in different crystal shapes. Mined diamonds grow in an octahedral shape (an octahedron is an 8-sided polyhedron: picture two pyramids back to back). Diamonds grown using the HPHT method grow into a cuboctohedron, or a 14-sided polyhedron whose faces are a combination of hexagons and squares. Finally, diamonds grown using the CVD method grow into a cubic shape. If the diamond is already cut, of course, you won’t be able to tell what the shape of the rough diamond was, and lab-grown diamonds can be cut into any shape a mined diamond can.

Optical Properties

When we talk about the optical properties of gemstones, we are referring to the way light interacts with the stone. Optical properties are broken down into brightness, fire, and scintillation.

• Brightness: the reflection of white light
• Fire: the scattering of white light into other colors
• Scintillation: the sparkling pattern of light and shadow on a gem’s face.

These factors depend on the gemstone’s cut. A mined diamond and a lab-grown diamond of the same size, color, cut, and clarity will exhibit the same optical properties. Given this fact, there would be no way to tell if a cut and set diamond were a mined diamond or a lab-grown diamond.

Infrared Spectroscopy

It would be reasonable to conclude from all of this that most people probably couldn’t tell the difference between a mined diamond and a lab-grown diamond. They both have the same chemical composition, they both can contain inclusions, and they both exhibit the same optical properties, the presence or absence of fluorescence doesn’t tell us anything definitive, and though the rough crystals grow in different shapes, the cut and polished end products are the same. The average person looking at your ring won’t ever know—that is, if they’re even aware of the existence of lab-grown diamonds.

One of the only truly reliable ways to tell the difference between a mined and a lab-grown diamond is to have a gemologist conduct an infrared spectroscopy test. Different elements absorb different wavelengths of light. With a spectroscope, a gemologist can analyze the wavelengths of light that are absorbed by the gemstone to determine the presence of elements other than carbon. It can also determine the exact concentrations of these impurities, which will differ depending on both the type of diamond and the origin of the diamond.

The Differences? Not Many.

Aside from an expensive spectroscopy analysis performed by an experienced gemologist, you’d be hard-pressed to tell a mined diamond from a lab-grown diamond. The bottom line is that lab-grown diamonds have the same unmistakable character and the same durability as mined diamonds. Whether you buy mined or lab-grown diamonds comes down to personal preference and budget. But no matter what kind of diamond you buy, you should make sure to receive a grading report. All Primo Lab-Grown Diamonds come with an IGI grading report detailing the origins and quality of your diamond.