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Diamond Education: How are Lab-Grown Diamonds Created?

Learn the differences between CVD, HPHT, and their respective growing processes

Lab-grown diamonds are an increasingly popular, attractively priced center stone option. In the past few years, we’ve seen a growing trend among consumers toward interest and acceptance of lab-grown diamonds.

Remember, your knowledge gives you the opportunity to build trust. Be prepared when your customers come to you for answers, or when the time comes to help your customers make an informed decision.

Read on to learn about the differences between natural and lab-grown diamonds as well as how lab-grown diamonds are created.

Natural Diamonds

Natural diamonds built the loose stone industry, and you can say they’re pretty timeless: they formed 1.0 to 3.5 billion years ago. Their age and their unrivaled cultural symbolism — “a diamond is forever” — support their logic-standing appeal.

Type I Diamonds

Type I diamonds contain nitrogen and account for 98% of natural diamonds. According to the cluster arrangement of those nitrogen atoms, this category is further subdivided into two types:

  • Type Ia diamonds are plentiful, about 95% of natural diamonds are type Ia. Their color varies from near-colorless to light yellow. These diamonds were nicknamed “cape” diamonds which were initially mined near Cape Province, South Africa. This category is further subdivided into two types: Type IaA and Type IaB.
  • Type Ib diamonds are extremely rare and typically a strong yellow in color. This yellow is sometimes referred to as “canary”.

Type II Diamonds

Type II diamonds have no measurable level of nitrogen and account for only 2% of natural diamonds. Then, they are further subdivided. Diamonds that do not contain boron are Type IIa. If containing boron, diamonds are Type IIb.

  • Type IIa diamonds have no measurable levels of nitrogen. They are usually light brown due to some deformation issues in their atomic structure but can also be colorless. Many of the world’s historical diamonds — like the Cullinan and the Koh-I-Noor — are type IIa.
  • Type IIb diamonds — unlike all other types — conduct electricity and exhibit beautiful blue or blue-grey shades due to the presence of boron. The Hope Diamond is the most famous type IIb diamond.


Did You Know?

Some IIb diamonds with trace amounts of boron remain colorless, yet still conduct electricity. Likewise, Moissanite is electrically conductive. Because of this, probe-type testers measuring for conductivity may falsely call out type IIb diamonds as Moissanite.

That’s quite a range for diamonds to fall into, but what about lab-grown diamonds? As it turns out, they play by slightly different rules — solely thanks to the method in which they’re grown.

Lab-Grown Diamonds

Lab-grown diamonds exhibit the same optical, physical, and chemical properties as natural diamonds. Unlike natural diamonds, which can be either type I or type II, all colorless lab-grown diamonds are type II.

While it is nearly impossible to detect lab-grown diamonds by sight, the growing process leaves behind evidence of any diamond’s origin. Advanced screening and testing equipment is necessary here. Just remember, no single device can do it all.

So, How Are Lab-Grown Diamonds Created?

Lab-grown diamonds got their start in the ‘50s. General Electric — yes, the power company — as the first to produce them on a mass scale for industrial use. H. Tracy Hall from General Electric grew their lab-grown diamonds through one process. Now there are two.

We’ll start with the first.

High-Pressure High-Temperature (HPHT)

This process dates back to 1954 when ASEA, a Swedish electrical company, first used this method, followed by the first industrial-quality mass production in 1961 by General Electric. In the 1970s, GE started commercially producing “gem-quality” HPHT lab-grown diamonds, which were yellowish with undesired noticeable black inclusions and didn’t get too much attraction. Fast forward to the 2010s where several companies managed to successfully grow larger sizes of near-colorless gem-quality diamonds for the jewelry industry. Since then, HPHT technology has come a long way, now growing colorless, flawless, lab-grown diamonds for use in jewelry.

The HPHT process grows diamonds using diamond presses, machines that mimic the extreme conditions that form diamonds within Earth’s upper mantle: intense pressure (725,000–870,000 PSI) and intense heat (2,300–2,900 degrees Fahrenheit). In this process, carbon in the form of graphite dissolves in molten metal flux and deposits as a diamond on a seed crystal. This process takes several days to a few weeks.

Chemical Vapor Deposition (CVD)

The CVD process was first invented in 1952 by William Eversole at Union Carbide.  This process allows diamonds to grow in an entirely different way than the HPHT process. CVD starts with a natural diamond slice or slab placed in a chamber and exposed to less extreme temperatures, approximately 1,200–3,000 degrees Fahrenheit, and lower pressure, 14–550 PSI.

Recent advancements have made this growth process more advantageous. Methane and hydrogen gas are injected into the growing chamber and bombarded by microwave energy to break their molecules into atoms. The combined atoms separate, forming a high-energy plasma cloud. The carbon atoms deposit onto the top layer of the seed, growing new diamond layers. Commonly, this process produces brown or gray diamonds which are later turned colorless through an HPHT annealing process. This process takes a few weeks to a couple of months.

The HPHT process grows diamonds using diamond presses, machines that mimic the extreme conditions that form diamonds within Earth’s upper mantle: intense pressure (725,000–870,000 PSI) and intense heat (2,300–2,900 degrees Fahrenheit). In this process, carbon in the form of graphite dissolves in molten metal flux and deposits as a diamond on a seed crystal. This process takes several days to a few weeks.

Stuller Lab-Grown Diamonds

At Stuller, we pride ourselves on our extensive diamond collection which includes a variety of natural and lab-grown diamonds. Included in these collections are a variety of shapes and sizes, graded and ungraded.

Lab-grown diamonds have shown a great increase in sales in recent years. As stated by the MVI Market Update, global lab-grown awareness and demand have grown to 81% as of 2023, and 72% of retailers are now offering lab-grown diamonds. Additional benefits to owning lab-grown diamonds are that 36% of shoppers can increase their budget when they have the opportunity to choose lab-grown diamonds. When purchasing a lab-grown diamond, customers can rest assured with the knowledge that all lab-grown diamonds are laser inscribed with an ID security number.

Stuller Screening

As a major supplier of diamonds, Stuller ensures that our customers can have complete confidence that their diamonds have been screened with thorough and robust practices that use the most advanced technology available. Every diamond that enters the building is screened thoroughly with in-house screening stations. This screening process includes two automatic melee screeners, twenty-five fluorescence imaging screeners for loose and mounted diamonds, three giant imaging screeners, eight fluorescence spectroscopy screeners, and finally, nine UV-transparency screeners. This doesn’t include the screening that Stuller’s suppliers do before they ship them. Stuller will continue to be extra thorough with their screening process by randomly taking samples of diamonds from our suppliers and sending them to laboratories to check the diamonds.


Heather Fontenot

Senior Director, Diamonds & Gemstones

Heather joined the Stuller loose stone merchandising team in August 2015 after attaining her bachelor's degree in Business Management from the University of Louisiana at Lafayette. Her natural curiosity and love of all things that sparkle and shine has pushed her to learn as much as she can about Earth's most precious possessions.