Synthetic diamonds are grown in a laboratory and have essentially the same chemical composition, crystal structure and physical properties as natural diamonds. They are not fakes, but they’re not natural.

When it comes to engagement rings, natural diamonds continue to occupy center stage. But there are newcomers on the block vying for attention. Once considered suitable only for industrial use, synthetic diamonds are now available in gem quality. Today they are offered in sizes and colors that make them viable options for engagement rings and fine jewelry. As you explore your engagement ring options, it pays to learn a little about them.

A Brief History of Synthetic Diamonds

Produced for industrial purposes since the 1950s, synthetic diamonds have been used in a wide variety of applications: telecommunications, laser optics, as abrasives and more. In 1970, researchers at General Electric created the first synthetic diamonds in a quality and size that could be faceted.

By the mid-1980s, manufacturers were able to grow commercial quantities of synthetic diamond crystals that could be cut and used in jewelry. Initially they were mostly small and yellow in color, but the quality of colorless gem-quality synthetic diamonds continued to improve over the ensuing decades. Synthetic diamonds can now equal natural diamonds in appearance.

Synthetic diamond produced by General Electric. Because of its color and size, it is not suitable for use in jewelry.

Here is a synthetic diamond produced by General Electric. Because of its color and size, it is not suitable for use in jewelry.

Pictured is the Alvadora, a vintage-inspired ring featuring a bezel-set center gem surrounded by lavishly detailed latticework and a halo of shimmering melee.

Brilliant Earth allows consumers to pick their own diamonds – natural or synthetic – and build their own rings. Pictured here is the Alvadora, a vintage-inspired ring featuring a bezel-set center gem surrounded by lavishly detailed latticework and a halo of shimmering melee. Courtesy: Brilliant Earth

Emerald-cut synthetic diamond ring with slender tapered synthetic diamond baguettes

Jewelry designer Scout Mandolin pairs an emerald-cut synthetic diamond with slender tapered synthetic diamond baguettes for a streamlined and elegant version of a traditional classic. Courtesy: Scout Mandolin, scoutmandolin.com

Emerald Cut ring with straight baguettes and pavé set round brilliant cut diamonds.

Scout Mandolin accents the center stone in his Allure Emerald Cut ring with straight baguettes and pavé set round brilliant cut diamonds. Courtesy: Scout Mandolin, scoutmandolin.com

How Are Synthetic Diamonds Made?

While natural diamonds may take billions of years to form, synthetic diamonds can be grown in a matter of weeks, using one of two processes:

1. High Pressure, High Temperature (HPHT): With this method, synthetic diamond is produced in a laboratory by mimicking the high-pressure, high-temperature conditions of natural diamond formation in the earth. The result is a distinctive crystal shape that is, for the most part, a combination of octahedral and cube faces with a flat base.

Distinctly shaped HPHT-grown synthetic diamond crystal

The shape of an HPHT-grown synthetic diamond crystal is distinctly different from that of natural diamond crystals.

8.52 carat [ct] octahedral shape crystal

This 8.52 carat [ct] crystal came from the small African country of Lesotho. It has the tell-tale octahedral shape of a natural diamond. Photo: Robert Weldon/GIA. Courtesy: Fusion Alternatives

2. Chemical Vapor Deposition (CVD): With this newer technique, synthetic diamonds are grown in an apparatus that uses moderate temperatures and very low pressures in a vacuum chamber. The CVD process involves heating a mixture of a hydrocarbon gas (such as methane) and hydrogen, which releases carbon atoms that then settle onto the cooler, typically square-shaped seed plate of natural or, more likely, synthetic diamond. This results in a square-shaped, tabular synthetic diamond crystal.

CVD synthetic diamonds exhibit distinctive features (such as ultraviolet fluorescence patterns) that indicate growth in a lab.

As grown, uncut CVD synthetic diamonds look nothing like natural diamond crystals. Some CVD synthetic diamonds exhibit distinctive features (such as ultraviolet fluorescence patterns) that indicate growth in a lab. In almost all cases, however, conclusive identification requires the scientific instruments and expertise that only a well-equipped gemological laboratory can provide. Photo: Orasa Weldon/GIA

Changing the Color of Synthetic Diamonds

Most HPHT synthetic diamonds are yellow or brown as grown, although some blue and near-colorless crystals are also produced. HPHT processes can also be used to enhance the yellow color or dramatically remove unwanted color so the diamond is on the colorless to near-colorless D-to-Z scale.

Most HPHT synthetic diamonds are yellow as grown

Most HPHT synthetic diamonds are yellow as grown and can be enhanced by post-growth treatments to change, improve or remove the color. Copyright: GIA & Tino Hammid

Irradiation, sometimes followed by high-temperature heating, is another common treatment process. It can change a synthetic diamond’s color to yellow, red, pink or green. Natural yellow, red, pink and green diamonds can be prohibitively expensive. Synthetic diamonds offer a more affordable alternative.

Synthetic diamonds can be found in a variety of attractive colors.

Synthetic diamonds can be found in a variety of attractive colors. The yellows set in jewelry range from 1.00 to 1.25 ct; the loose lab-grown diamonds are all less than 1 ct. The colorless diamond accent stones are natural. Photo: (Diamonds) Harold & Erica Van Pelt/GIA. Courtesy: (Jewelry) Gemesis Corp.

A complex, multi-step process that also involves HPHT treatment can turn brown lab-grown diamonds into more marketable red synthetic diamonds.

Do Synthetic Diamonds Look like Natural Diamonds?

Synthetic diamonds have nearly the same physical and optical properties of natural diamonds. They are just as hard, and they are available in a range of colors and qualities. Just like natural diamonds, they can have an excellent cut—and, therefore, excellent fire, brightness and scintillation—or they can have a poor cut or anything in between. It all depends on the quality of the synthetic diamond and the skill of the cutter.

CVD synthetic diamonds display the same color and brightness of comparable quality natural diamonds.

These CVD synthetic diamonds display the same color and brightness of comparable quality natural diamonds. They range in size from 0.24 to 0.90 ct. Photo: Robert Weldon/GIA

How Do You Identify a Synthetic Diamond?

Because the optical and physical properties of today’s synthetic diamonds are nearly identical to those of natural diamonds, identifying synthetic diamonds is complex. Only a gemological lab with equipment that allows for advanced testing techniques can make an authoritative determination if a diamond is natural or synthetic.

Metallic inclusions may provide a clue that the diamond is synthetic.

Metallic inclusions may provide a clue that the diamond is synthetic. Here are several seen at 20× magnification. Photo: John I. Koivula/GIA

To protect the consumer and eliminate any possible confusion, GIA’s laboratory issues two different reports: one for natural diamonds and one for synthetics. GIA Synthetic Diamond Grading reports provide a full 4Cs assessment but with color and clarity descriptions that are more general than those used for natural diamonds. GIA also laser inscribes the girdles of all synthetic diamonds with the phrase “laboratory grown” and the report number. The report itself looks different from that used for natural diamonds.

A GIA Synthetic Diamond Grading Report.

A GIA Synthetic Diamond Grading Report.

A GIA Diamond Grading Report for a natural diamond.

A GIA Diamond Grading Report for a natural diamond.

How Are Synthetic Diamonds Graded?

Synthetic diamonds undergo the same rigorous grading process as natural diamonds. However, the color and clarity scales are broader with fewer grade terms. This is because GIA has yet to see the same continuum of grades with synthetic diamonds.

The GIA Synthetic Diamond Color Scale has five grades: Colorless, Near Colorless, Faint, Very Light, and Light.

The GIA Synthetic Diamond Clarity Scale has six grades: Flawless, Internally Flawless, Very Very Slightly Included, Very Slightly Included, Slightly Included, and Included.

Are Synthetic Diamonds Good?

Synthetic diamonds are neither good nor bad. Purchasing a diamond is a deeply personal experience. It is a symbol of everlasting love. So the real question is, what’s important to you? That’s what should guide your purchase decision when it comes to buying a natural or synthetic diamond – just make sure you know the difference.

10.02 ct colorless (E-color equivalent), HPHT-grown emerald cut is the largest faceted synthetic diamond reported to date.

Synthetic diamonds have come a long way from the small, industrial-quality yellow crystals of just a few decades ago. This 10.02 ct colorless (E-color equivalent), HPHT-grown emerald cut is the largest faceted synthetic diamond reported to date. Photo: Johnny Leung/GIA

Ready to shop for an engagement ring? Check out our Guide to Diamond Engagement Ring Terms to help you have a meaningful conversation with your jeweler.