Updated: Mar 16
By Julia Griffith FGA DGA EG
Welcome to The Gem Academy - the go-to place to advance your gem and gemmology knowledge.
What's in this article?
Production - Properties - Are LGDs identical to natural diamonds? - Other differences - First synthesised diamonds - Popularity of LGD's - Possible sizes - Possible qualities - Possible colours - Production volumes - Cost to buy - Long-term value - Future worth
Laboratory-grown diamonds seem to be everywhere, and their prevalence is on the rise as more consumers learn about these products. Let's get our "diamonds in a row" with this introductory article on the what's, why's and prices of laboratory-grown diamonds.
What is a laboratory-grown diamond?
A laboratory-grown diamond is a diamond that has been artificially produced in a laboratory or factory. The term "artificial" does not mean "fake", but rather refers to a product that has been manufactured using machines as opposed to forming naturally.
These artificial diamonds have the same chemical composition as natural diamond and has the same crystal structure. Therefore, natural and laboratory-grown diamonds are the same material and possess the same properties as one another.
Fig. 1.1. The crystal structure of diamond, showing carbon atoms covalently bonded together. This structure is the same for both natural and laboratory-grown diamonds, thus, they are the same material.
There are three terms to describe these products that are approved by most organisations; "laboratory-grown diamond", “laboratory-created” and "synthetic".
Many jewellery professionals (myself included) colloquially use the following short-hand terms; "lab-created", "lab-grown", or "LGD", which stands for “laboratory-grown diamond”. Please note, that depending on where you are based, there are different recommendations for the terminology you use on official documentation, promotions and sales descriptions, which link to trading standards.
Why "cultured" is not an appropriate description for laboratory-grown diamond
How are laboratory-grown diamonds produced?
Two main production methods are used for making commercial gem-quality laboratory-grown diamond; HPHT and CVD.
1. High-pressure, high-temperature (HPHT)
Fig. 1.2. The growth of laboratory-grown diamond through HPHT synthesis.
HPHT synthesis grows laboratory-grown diamonds from a metallic flux/carbon solution under high temperatures and pressures. The temperatures are typically within the range of 1300 – 1600°C, and the pressures are between 5-6 gigapascals (GPa).
A few pieces of apparatus have been created to supply the heat and extreme pressures required. The main apparatus used is the cubic press - a huge machine that utilises six hydraulic anvils to put pressure onto the reaction cell where the diamond grows. The cubic press was developed in China, who currently produce around 90% of all laboratory-grown diamonds. Cubic presses allow for multiple diamonds to be grown within one press and/or larger crystals to be grown. In some factories, this can be up to 200 individual small diamonds or a dozen or so larger crystals up to 10cts each in weight.
2. Chemical vapour deposition (CVD)
Fig. 1.3. The growth of LGD diamond through HPHT synthesis.
CVD synthesis precipitates laboratory-grown diamond out of plasma using methane (CH4) as the carbon source. This process uses sub-atmospheric pressures (<0.25 atm) at temperatures around 800-1200°C.
The carbon atoms are deposited in layers ontop of a diamond seed (typically made from HPHT laboratory-grown diamond). CVD growth is slow if pure carbon structures are grown, taking an hour to grow just 0.0001mm. However, faster growth times can be achieved if a small amount of nitrogen is added to the growth chamber. This can grow crystals around 6-10ct in weight within 3-4 weeks.
The resulting crystals have a brown tint due to internal strain caused by their relatively fast growth times. These crystals are commonly subjected to HPHT treatment to remove the brown tint. This involves placing the crystals into HPHT apparatus for a short period of time (a few minutes to half-an-hour), which "decolourises" the laboratory-grown diamonds and results in more colourless stones.
Fast growth with subsequent HPHT treatment is said to be the more common process for CVD laboratory-grown diamonds. It is estimated that 75% of the colourless CVD laboratory-grown diamonds on the market have been grown and then treated by HPHT or LPHT (low pressure high temperature) treatments.
Laboratory-grown diamonds vs. natural diamonds
As natural diamonds and laboratory-grown diamonds are the same material, they exhibit the same properties. They have many identical optical properties such as the way they interact with light. These properties are responsible for their unparalleled adamantine lustre, high dispersion and brilliance. They also share many physical properties, such as; hardness, toughness and stability.
Fig. 1.4. This table compares some of the properties of natural and laboratory-grown diamonds. These are mostly the same, except for possible impurities.
Are laboratory-grown diamonds identical to natural diamonds?
Fig. 1.4. displays the parallels between natural and laboratory-grown diamond properties. Many properties are the same because they are the same material, but it can not be said that the two products are identical.
A key difference is possible impurities. These vary slightly due to the different growth origins of natural and laboratory-grown diamonds. Impurities are minor amounts of elements within the crystal structure that are not part of the essential chemical composition. I.e. a diamond with or without impurities still classifies as a diamond.
Impurities make up just a fraction of a percent, yet are often characteristic of origin. Natural and laboratory-grown diamonds have different growth environments that have different impurities available within them. The type of impurity, and any aggregates of impurities, is one of the main ways that a gemmologist can determine natural or laboratory-grown origin.
Examples of these differences include a diamonds fluorescence and phosphorescence, which is caused by impurities, and so can differ for the different origins. Beyond this, advanced equipment can display the absorption and emission of light from a diamond structure, which, again, is linked to impurities.
For this reason, laboratory-grown diamonds are most accurately described as having "essentially" the same chemical composition as natural diamonds as the common impurities and aggregates can vary.
Fig. 1.5. The crystals of natural, HPHT and CVD laboratory-grown diamonds.
Other differences between natural and laboratory-grown diamonds
The types of inclusions found in a diamond are also exclusive to natural and laboratory-grown origins. Any matter that has been trapped within a diamond is a reflection of its growth environment. Therefore, natural diamonds have a different suite of inclusions compared with laboratory-grown diamonds and, likewise, inclusions deriving from HPHT and CVD synthesis differ from each other. When these inclusions are big enough to see and identify, we can separate natural, HPHT and CVD laboratory-grown diamonds through observing these features.
A final key difference between natural and laboratory-grown diamonds are the directions that the crystals grow in. These different growth directions are sometimes visible within the diamonds as internal grain lines (also known as "growth lines"), which can be an identifiable feature . The difference in growth directions is reflected in the rough crystal forms of natural and laboratory-grown diamonds and can also be seen in cut stones with the use of UV light.
Beyond the physical, there are also relative differences such as rarity and value, which we will touch on later in this article.
3 ways to separate natural and laboratory-grown diamond through observation
Fig. 1.6. A HPHT Belt apparatus owned by General Electric (GE), which was the first company to announce the successful synthesis of diamond in 1955. © MiSci
When were laboratory-grown diamonds first created?
The dawn of the laboratory-grown diamond began in the early 1950s. The main push to create artificial diamond was the deficit in supply industrial abrasives during World War II. Diamonds are excellent abrasives due to their extreme hardness, high thermal conductivity and low thermal expansion. This demand for abrasives spurred research and experimentation in diamond synthesis, resulting in the two processes most commonly used today; HPHT and CVD.
The first diamonds from both processes were tiny. CVD synthesis could only produce extremely thin layers of polycrystalline diamond material deposited on a substrate and HPHT could grow three-dimensional diamonds with diameters of approximately 1 millimetre.
The first HPHT lab-grown crystals were immediately useful as diamond grit and, so, HPHT processes took the lead in the production of industrial diamonds, which reached 40 million carats per annum by the late 1960s - just 4 million carats short of the entire natural diamond annual production (Ref: Eric Bruton, "Diamonds").
It took a lot longer to successfully produce laboratory-grown diamonds suitable for use in the jewellery industry. The first challenge was size. Facetted laboratory-grown diamond crystals typically yield just 30-40% weight from the original rough crystal, so large crystals were required, which proved challenging to grow.
In 1971, HPHT laboratory-grown diamonds that were considered "gem-quality" were first announced. These were approximately 6mm in diameter. These were successfully created through a process known as the "temperature gradient method", which utilises a diamond seed at the base of the cell so all the carbon crystallises in one location, as opposed to hundreds of locations throughout the cell.
CVD diamond synthesis was on a much slower journey. Despite the first successful synthesis occurring in 1952, the first gem-quality facetted stones only entered the market in the 2000s.
Fig. 1.7. Sorting HPHT laboratory-grown diamond melee.
Why is the popularity of gem-quality laboratory-grown diamond only rising now?
Although gem-quality laboratory-grown diamonds have been possible for the past 50 years, the first were very expensive, as their cost has to factor in the time, effort, research, equipment and experiments - both those that were successful and those that failed - into the resulting products value.
Production, supply and demand are part of a cycle. When laboratory-grown diamonds were first produced, they were expensive and the demand was very low. A low amount of sales leads to a continued high price for the product - and, so, the cycle continues.
Generally speaking, the demand for laboratory-grown diamonds has finally outweighed the cost of the set-up and production for established companies. This steady increase in the supply of laboratory-grown diamonds has led to an increase in awareness and demand - resulting in a decrease in the cost of production.
Today's large consumer demand has made it possible for more people to create laboratory-grown diamonds and create a successful business.
Diamond - the supermaterial gemstone
What sizes are possible in lab-grown diamonds?
Fig 1.8. The largest CVD-grown LDG produced thus far. Equivalent to a "I" colour grade (as-grown) and "VS" clarity. This diamond was produced by WD Diamonds in 2018.
Laboratory-grown diamonds can be grown in a range of sizes in both HPHT and CVD processes.
Small melee diamonds (facetted diamonds under 0.20ct) are mainly produced by HPHT synthesis, as it is less economical for CVD producers to grow diamonds specifically for cutting small stones. However, off-cuts of larger CVD stones may be cut as melee.
The most common size for laboratory-grown diamond melee is under 0.10ct and may be cut as small as 0.005ct. Laboratory-grown diamond melee cause the biggest issues for those trying to check for diamond origin. The small sizes and styles of setting limits testing and the individual value of a melee diamond does not justify advanced testing by a gemmological testing laboratory unless testing occurs in bulk.
Larger facetted diamonds are also produced by both HPHT and CVD, with the most popular sizes being around 1.00 - 1.50ct. Currently, fashioned laboratory-grown diamonds over 5ct are uncommon on the market. However, producers are getting better at producing larger stones.
The largest facetted HPHT laboratory-grown diamond weighs 20.22ct and was produced by New Diamond Technologies in 2018. The largest CVD laboratory-grown diamond weighs 9.04ct. This was grown in 2018 by WD Lab Grown Diamonds.
In 2015, the largest HPHT diamond was 10.08ct, and the largest CVD diamond was 2.51ct. This demonstrates how the capabilities of laboratory-grown diamond production is quickly improving.
What qualities are possible in lab grown diamonds?
Fig. 1.9. Rod-like and Ash-like metallic inclusions - common forms of metallic flux, which can been trapped in HPHT lab grown diamond as it grows.
The colour and clarity of laboratory-grown diamonds have been steadily improving since the first creation of gem-quality laboratory-grown diamonds in the 1970s. Not all laboratory-grown diamonds are “perfect”, but high-quality laboratory-grown diamonds are the norm.
The typical qualities differ between the different synthesis methods. HPHT laboratory-grown diamonds typically have good clarity of SI1 or higher, with many being within the VS to VVS range.
The colour grades for HPHT laboratory-grown diamonds are typically very high. The most common colour grade is equivalent to a colourless “E” grade.
In CVD laboratory-grown diamonds the clarity grade is typically higher than for HPHT, most commonly being equivalent to a VS grade or higher.
Contrary to popular belief, the colour grades are typically lower than HPHT laboratory-grown diamonds. The average colour grade for CVD laboratory-grown diamond is equivalent to an “I” grade, even after HPHT treatment. Colourless CVD diamonds (equivalent to D-E-F grades) are also possible, but less common.
Although low-quality laboratory-grown diamonds are possible for both production methods, these are the less common qualities on the laboratory-grown diamond market. This is the opposite for natural diamonds, where lower qualities are more common and high qualities are rarer.
High-quality laboratory-grown diamonds are somewhat indistinguishable from high-quality natural diamonds by observation alone. After all, they are the same material with the same chemical composition and crystal structure, and without inclusions - a gemmologists job is somewhat harder.
3 ways to separate natural and laboratory-grown diamond through observation
What colours are possible in lab grown diamonds?
Fig. 1.10. A selection of HPHT lab grown diamond and one CVD lab grown diamond (in setting). These colours are all "as-grown" and have not been treated post-growth.
HPHT laboratory-grown diamonds can be grown in colourless, yellow and blue. These colours are produced with the presence or absence of the same impurity elements that cause these colours in nature*. Nitrogen impurities cause yellow. Boron impurities cause blue. An absence of these impurities results in a colourless diamond. Rarely, green colours of HPHT laboratory-grown diamond are produced by including high amounts of nitrogen and boron together.
CVD laboratory-grown diamonds are only commercially grown as colourless to brown diamonds, and then often treated to decolourise them.
Both types of laboratory-grown diamond can be treated to produce other colours. Irradiation can create green and blue. Irradiation and annealing can produce pink hues. A combination of HPHT, irradiation and annealing can produce red.
*Please note: They often occur in different aggregates and volumes.
How many laboratory-grown diamonds are being produced each year for the jewellery industry?
Fig. 1.11. A factory floor at former company Apollo Diamond Inc., showing multiple pieces of HPHT apparatus, known as BARS apparatus.
It has been estimated that 7 million carats of rough HPHT laboratory-grown diamond and up to 3 million carats of rough CVD were produced for the jewellery industry in 2020. This would equate to approxiamtely 3-4 million polished carats in total, based on an average yield of 30-40% from the rough crystals. This would equate to billions of individual polished stones from 0.005ct upwards.
According to estimations by Morgan Stanley, it was predicted that laboratory-grown diamond melee would account for 15% of diamonds jewellery sales in 2020, and that larger diamonds would account for 7.5% (Ref: Morgan Stanley).
This is different to diamond industry analyst Paul Zimnesky's predictions from 2018, which was for lab-grown diamonds to have approximately 2% of the diamond jewellery market in 2020 (Ref: Paul Zimnesky).
How much does a laboratory-grown diamond cost to buy?
A 0.59ct HPHT laboratory-grown diamond. Purchased for £320.00 in Dec 2020.
This is a hard question as the price keeps changing.
In 2015, they were approximately 85% of the price of equal quality natural diamonds (Ref: Paul Zimnesky). Today, the average price is around 30-35% compared with equal quality natural diamonds.
Lightbox, by DeBeers, retails at prices approximately 20% that of natural diamonds, selling at $800 USD per carat. It is difficult to assess the exact relationship between Lightbox diamonds and natural diamonds as they are not sold with individual colour or clarity grades.
Example of price difference:
A 1.02ct high quality, high colour laboratory-grown diamond (E, VS1, excellent cut, round brilliant) is approximately $2050 USD on James Allen, a popular online retailer (05/03/21). Compared with a natural diamond of equal quality and beauty, the natural is priced nearly 3x higher at $6500 USD on the same website. In this example, the lab-grown diamond is valued at 31.5% of a comparative natural.
Will a laboratory-grown diamond hold its value?
Historically, they haven't. A laboratory-grown diamond purchased 5 years ago can be purchased today for less than half the price.
Will they have a good resale value? No, they won't. But, bear in mind - not many things do. There is often a huge difference between retail and resale price. Natural diamonds included. The difference between natural and laboratory-grown diamonds is that natural diamonds have consistency in their retail and resale prices, which may fluctate over time, but overall have an upward trend. This is not the case with laboratory-grown diamonds, which thus far has been on a steep downward trend.
Will the prices of laboratory-grown diamonds continue to decrease?
Maybe. It's hard to say. As the production price of each laboratory-grown diamond drops and competition in retail increases - the retail price may continue to decrease. Then again, it has to reach a threshold at some point. The question is whether this point has been reached or whether there is further to go.
As discussed, the production of laboratory-grown diamonds involves several costs; for initial set up, raw materials, production, staffing, admin, sorting, cutting, laser engraving, fees for lab-grown diamond reports... the list likely goes on.
On top of this, there is, of course, the profit margins necessary for the producers, wholesalers and retailers so they can keep doing business. Therefore, there must be a limit to how low the price of laboratory-grown diamonds can go. Where is this limit? I have no idea.
One area that may see further decreases in price are the larger laboratory-grown diamonds, which are those above 2-3ct in weight.
As an example of current large diamond pricing, this 3.30ct laboratory-grown diamond (E, VS1, excellent-cut, round brilliant) currently retails at $19,570 ($5,930 per carat). This natural diamond of 3.24ct of equivalent quality is priced at $75,100 ($23,179 per carat). In this example, the price of the lab-grown diamond is 25% of the price of the comparable natural.
The pricing of these stones is currently in-line (or even just below) that of smaller laboratory-grown diamonds. However, the actual sale price of these stones are very high, as they are compared with natural diamonds which have very high values placed on them due to rarity.
This practice of pricing laboratory-grown diamonds against a compable natural diamond has been bought into question by several natural diamond industry professionals. The opinion is that the pricing of a natural rare product, such as diamond, should bear no representation on the pricing of an artificial product that has the capability to be mass produced.
“The cost of these synthetic diamonds will go down to production costs plus a competitive profit margin. There is no shortage.” says Martin Rapaport, the owner of Rapaport Magazine and RapNet - the natural diamond pricing guide.
If the pricing of laboratory-grown diamonds changes into a more traditional calculation of: cost of production + profit margin = retail price, significant price drops may be ahead for larger laboratory-grown diamonds.
This is hypothetical of course - we can only wait and see what happens.