What Should You Know Before Buying Lab-Created Diamonds?
Over the last few years purchases of lab-created diamonds has increased substantially. There are many reasons people choose lab-created over mined diamonds including cost, peer pressure, opinions about the mining industry, and love of technology. Buying lab-created is similar to buying mined in many ways (e.g. the 4 C’s) but there are a few things to consider that are specific to these gemstones. So, what do you need to know if you’re thinking of buying a lab-created diamond?
Firstly, yes, they are most definitely real diamonds! As described in the industry, they “possess the same physical, chemical, and optical properties as natural mined diamonds”. A bunch of fancy words to say, they are mineralogically indistinguishable from mined diamonds because they ARE diamonds. The real difference is how and where they grow.
Lab-creation uses two methods: high pressure high temperature (HPHT); or carbon vapor deposition (CVD). HPHT replicates the conditions in the earth’s mantle where natural diamonds form, using mechanical presses and heat. A diamond seed is placed within carbon rich powder (graphite or diamond). Under extremely high temperatures and pressures, the pure carbon melts and a diamond crystal grows nucleating from the seed (all crystals grow from a nucleation point). CVD attempts to replicate diamond formation in interstellar gas clouds. It starts with a diamond slice placed in a chamber filled with carbon rich gases. The chamber is heated to ~800 deg C (1472 deg F). The gas components are dissociated using microwaves, photon irradiation, or plasma. The carbon particles then deposit onto a seed layer by layer. Both processes create diamond rough in a matter of weeks. Once cut, they look just like any other diamond.
Lab-creation uses two methods: high pressure high temperature (HPHT); or carbon vapor deposition (CVD). Both processes create diamond rough in a matter of weeks. Once cut, they look just like any other diamond.
Comparison of HPHT and CVD diamond crystals before cutting.
The HPHT method was initially developed by GE (1954) to grow diamond for industrial uses. Retail jewelry HPHT diamonds became available in the mid-1990s. CVD was created in the 1980’s as an industrial process to produce very pure high-performance solid materials. CVD diamonds have been commercially available since 2007. CVD is often advertised as a lower cost and energy intensive alternative to HPHT.
HPHT diamonds are cuboctahedrons with 14 growth directions. The gas in the chamber contains nitrogen which, when incorporated in the crystal, can give a slight yellow color. This is common feature in mined diamonds as well. CVD diamonds are cubic with only one growth direction (up). This can cause strain in the crystals which, in diamonds, results in a brown color.
The two methods actually produce different diamond types. Diamonds come in 2 types (I & II, with additional subtypes). Type I diamonds are by far the most common. These diamonds contain nitrogen as their main impurity, while Type II diamonds have no measurable nitrogen or boron impurities. HPHT diamonds are Type I, with nitrogen and other impurities. CVD diamonds however, are “chemically pure”. The disassociated gas contains no nitrogen or boron impurities that can be incorporated into the crystal structure - resulting in the production of a Type IIa diamond. In nature Type IIa are EXTREMELY rare – only 1-2% of natural diamonds are this type. But all CVD lab-grown diamonds are Type IIa. This is one way lab vs natural diamonds are differentiated.
Example GIA Laboratory Grown Diamond Report
This CVD grown diamond is clearly identified as such in the Comments Section, as is the post growth treatment this stone has undergone. Ask to see a Lab-report for any major lab-grown diamond. Check for method of growth and if there is any evidence of post-growth treatment.
Because CVD diamonds are often brown, they commonly undergo post growth treatment. These diamonds are treated with HPHT to remove the structural irregularities in the crystal lattice and reduce the brown color. The post growth treatment negates the energy “savings” and results in a treated stone. Many lab-grown diamonds come with lab grading reports. These will indicate the value factors of the stone. It will also state whether the stone is “as grown” or has been treated. Treated stones are always worth less than untreated stones. Pay attention to the grading report when purchasing these stones.
Meylor Global - 20.23ct Fancy Vivid Yellow Orange cushion cut CVD diamond
Initially, the maximum size of lab-created diamonds was small, and the best quality was unattainable. The technology continuously improves, impacting the size, quality, speed and cost of these stones. This now also includes fancy-colored diamonds. Currently the record size for a CVD diamond is held by Mumbai-based Ethereal Green Diamond with a reported a 30.18-carat emerald-cut, H-color, VS2-clarity diamond, named Pride of India (June 2022). British company Meylor Global owns the world record 20.23ct Fancy Vivid Yellowish Orange, VS1 cushion cut lab-created diamond, cut from a crystal weighing 55.94 cts. However, in Feb 2022, the International Gemological Institute (IGI) announced it had analyzed a record setting, lab grown, fancy blue rough diamond weighing 150.42 carats, created by British company Meylor Global which, when cut, could surpass the previous fancy color record holder.
Most of the fancy-color CVD diamonds fall within the pink color spectrum. But these colors are mostly due to multiple post-growth treatments, including HPHT annealing, irradiation, and low-temperature annealing. With HPHT diamonds, the fancy colors are mostly as-grown and due to chemical impurities, as with natural diamonds. The exceptions are: pink, which is developed with post-growth irradiation and low-temperature annealing; and green, which can be as-grown, or can be due to laboratory irradiation.
It is a myth that lab-grown gemstones are inclusion free
Research at GIA laboratories in Carlsbad, CA show that both HPHT and CVD diamonds have the same range of clarity grades as found in natural diamonds. This is also true of fancy colored stones.
Just like mined diamonds, a lab grown diamond’s value is determined by quality values of carat, cut, clarity and color. It is a myth that lab grown diamonds are all “perfect”. Many have inclusions and they may not be completely colorless. HPHT and CVD synthetics span the entire clarity scale. This is not a method for differentiating natural vs lab grown diamonds. There are no reliable visual factors to help identify potential CVD synthetics, and the metal flux inclusions that were used in the past to identify HPHT diamonds are not commonly visible.
When purchasing any diamond, it’s important to find the right balance between quality and budget, as well as the emotional factor. Many lab grown diamonds sold in retail have third party lab reports. These will describe the size (carat), clarity, color, and cut proportions of the stone. The “best” stone is not necessarily the biggest one. The other 3 factors can make a huge difference on the price, value and ultimate beauty of the stone. The difference between a lab report for a natural diamond and one for a lab created stone is mostly in the notes, not the quality factors. The report will identify the stone as lab created, it will indicate which process (HPHT or CVD), it will show the “Lab Grown #########” laser inscription (with identification number) on the diamond girdle, and it will indicate whether it is “As Grown” or has undergone secondary post growth treatment.
An example IGI Laboratory Grown Diamond Report showing a CVD diamond with no evidence of post-growth treatment.
People often focus on diamond resale value as a determination of its inherent value. “Value” in this context is determined by the quality of the stone and its rarity (supply & demand). The price of diamonds (natural and lab) fluctuates over time. Lab-created diamonds are cheaper than natural diamonds because the producing cost is lower, and they only take weeks to create. Diamond mines can easily take 10-20 yrs of exploration and analysis work before they ever begin production. As they mine deeper into the kimberlite or lamproite pipes, cost remain high. As HPHT and CVD technology improves, and supply increases, the prices of lab created diamonds will decrease.
Both Natural and Lab-grown diamonds have dropped in value recently
The long-term value of lab grown diamonds is uncertain at this time. That said, the price of many natural diamonds has also been declining over the last couple of years because demand is down. If you aren’t in the jewelry trade, focusing on resale value will take the joy out of purchasing a diamond.
An example of the decline in natural diamond prices in 2022 from Rapaport News.
Diamonds have been desirable for centuries. They really are beautiful gemstones. This brings us to the emotional factor. Why do jewelers sell various sizes, quality, style of cut, and style of settings of diamond jewelry? Because not everyone likes the same thing. Certainly, price is a factor, but there is an emotional connection when one finds the diamond that speaks to them.
So, which is better, mined or lab created?
There is no absolute answer to that question. It is entirely dependent on your wants and values. Don’t be guilted into buying a diamond you don’t absolutely love. When you look at it, you should love it, period! For some, the romance of mother nature’s creation is supreme! For others, the technology is super fascinating! And others don’t care at all as long as it’s pretty! Be aware of what you’re buying, shop around, find the one that is right for you. That is all that really matters!
Reference Material
Gem Certification & Assurance Lab (GCAL) - https://www.gcalusa.com/
IGI – International gemological institute https://www.igi.org/
GIA - https://www.gia.edu/
Meylor Global - https://meylorglobal.com/
Feb 1, 2022, IGI Report of world record blue lab grown diamond. https://www.igi.org/press/igi-analyzes-record-150-carat-rough-lab-grown-diamond/
https://www.gia.edu/hpht-and-cvd-diamond-growth-processes
https://www.mygemologist.com/learn/lab-grown-diamonds/
http://caratsystems.com/index.html
http://ndtcompany.com/
Sally Eaton-Magaña and James E. Shigley, 2016, Observations on CVD-Grown Synthetic Diamonds: A Review, Gems & Gemology, Fall 2016, Vol. 52, No. 3
Wuyi Wang, Stephanie Persaud, and Elina Myagkaya, 2022, New Record Size for CVD Laboratory-Grown Diamond, Lab Notes, Gems & Gemology, Spring 2022, Vol. 58, No. 1
Sally Eaton-Magaña, James E. Shigley, and Christopher M. Breeding, 2017, Observations on HPHT-Grown Synthetic Diamonds: A Review, Gems & Gemology, Fall 2017, Vol. 53, No. 3
https://www.igi.org/press/igi-certifies-worlds-largest-lab-grown-diamond-30-carats/