We are talking about
Crystalized carbon (C) in the cubic system and arranged tetrahedrally within the grid.
As with natural diamond, this configuration gives the material properties that make it unique.
Therefore, we are not speaking of an imitation but of an authentic diamond produced by artificial synthesis methods made by man rather than by nature.
Initial attempts to produce the exact synthetic counterpart of diamond in the laboratory date back to the late 19th century, although the first historical success was recorded in the early 1950s when researchers at the American company, General Electric, synthetized the first small diamond crystals.
About 20 years later, General Electric was also the first to create synthetic diamonds large enough to be used as gems. This success was followed by the Japanese company, Sumitomo, and De Beers in the 1980s and by Russian laboratories in the ‘90s.
The HPHT production method
This method is based on the conditions that led to diamond formation in nature, i.e. high pressure and high temperature.
Crystal seeds, a metal alloy/solution (e.g. nickel and iron), which acts as an amalgamate/catalyst, and the nutrient (usually graphite) are placed inside the reaction cell and exposed to high pressure and high temperatures (between 1400 and 1600° C and between 50 and 60 kbars) using heating elements and presses.
The carbon dissolves into the amalgamate and then deposits on the crystal seeds in diamond form, usually in a part of the cell where the temperature is lower.
HPHT method BARS
HPHT method TOROID
HPHT method CUBOID
An important problem to face in this synthesis method is keeping any nitrogen responsible for the yellow-green to brown colouring of the synthetized crystals at bay.
Using new metal alloys as amalgamates, with the addition of particular elements (such as aluminium, cobalt or copper) fixes the nitrogen so that it cannot go back into the diamond grid.
Colourless diamonds (like lla diamonds) or those with a slightly bluish colour due to a very slight quantity of boron (type Ilb), are thus obtained.
CVD SYNTHETIC DIAMONDS
This method has the advantage of taking place at low pressures of about 10-200 torr.
A plasma is created in the chamber that breaks the molecule of the methane or other carbon-containing gas.
The carbon is then deposited in diamond form on a substrate usually made of tiny diamond seeds.
Colourless, CVD synthetic diamonds are generally of the Ila type, i.e. purely carbon.
In order to eliminate any possible brown components in crystalized diamonds that may occur with this method due to dislocations, the stones are subsequently subjected to an HPHT treatment which can eliminate them.
Under the microscope, synthetic HPHT diamonds often show characteristic growth shapes, correlated to sectors of cubic and octahedral growth.
This growth can be found in zonings of various fluorescence or in the colour distribution within the stone that follows these growth sectors.
Characteristic inclusions, not always present, are amalgamate residues that look like black and opaque inclusions with a metallic shine.
Colour zoning and structure lines in HPHT synthetic diamonds that follow the growth sectors
Characteristic inclusions, not always present, are amalgamate residues that look like black and opaque inclusions with a metallic shine or large groups of punctiform inclusions (probably minute particles of dispersed amalgamate).
Metal amalgamate inclusions in colourless HPHT synthetic diamonds
Examples of inclusions in HPHT synthetic diamonds
CVD synthetic diamonds can have minute, dark inclusions (carbon residues) with tension streaks probably generated by subsequent heat treatment used to improve the colour of the gems.
Examples of inclusions in CVD diamonds
Many HPHT synthetic diamonds have a typical fluorescence that ranges from yellow to a yellowish green under UVL (365 nm) and UVC (254 nm).
The impurities that are absorbed in the synthetic diamond structure during its growth tend to concentrate in particular growth sectors, that is, they generate characteristic cross-shaped or octagonal fluorescence shape, that are not found in natural diamonds.
Unlike natural diamonds, the reaction is more intense at short wave than long wave.
Natural diamonds generally show a variable degree of quite uniform blue fluorescence (yellow is much rarer and green or pink even more so) which is, in any case, more noticeable at long wave than at short wave.
Luminescence effects that follow cubo-octahedral growth directions in a diamond
The usually persistent presence of phosphorescence (extremely rare in nature and atypical in colourless stones) is a good identification sign.
In fact, llb-type diamonds are extremely rare in nature (containing boron) which only usually have this effect for a short time.
A particular characteristic of diamonds produced with the HPHT method is that they have few or only slight abnormal birefringencies, unlike natural diamonds. In CVD synthetic diamonds, abnormal birefringencies are generally similar to those in natural, lla-type diamonds, that is, they have a kind of trellis, often going in the same direction as the crystal deposit.
There are, however, CVD synthetic crystals with an «optic» quality (THEREFORE OPTICALLY PERFECT AND HOMOGENOUS) with no abnormal birefringencies.
Abnormal birefringencies in HPHT synthetic diamond. When present, they are cross-shaped
Abnormal birefringencies in CVD synthetic diamond
Infra-red spectrophotometry is ideal for helping to recognize the type of diamond, or rather, to check for the presence or absence of traces of some fundamental elements. IRS thus has the potential information for isolating diamond types that could be compatible with synthetic production.
Colourless synthetic diamonds are type lla (nitrogen in such small quantities that it cannot be detected instrumentally with IR), while blue diamonds, like their natural counterparts, are type llb (presence of boron). Type llb, or rather, traces of boron, can often be found in many colourless synthetic diamonds. Pink synthetic diamonds have also been seen on the market due to a subsequent irradiation treatment and heating at low temperatures. It should be remembered that, due to the presence of nitrogen, the initial productions foresaw yellow colouring in various shades of brown or greenish-brown. Some diamonds of this type, treated with irradiation, have been known to become a very bright red.
In UV-VIS-NIR spectrophotometry, the lb component in yellow-green synthetic diamonds generates an absorption that starts at 500 nm and goes towards ultraviolet.
Many diamonds show a series of absorptions, between 470 nm and 700 nm, with a more evident absorption at 658 nm. These peaks are due to the presence of nickel within the crystalline structure in the catalyst.
lla-type colourless synthetic diamonds are transparent up to 270 nm.
The presence of elements like nickel, iron, aluminium, cobalt, copper or other metals used in the growth, can be identified through chemical analysis with X-ray fluorescence (EDXRF).
Centres of diagnostic colour can be detected through photoluminescence due to traces of impurities. In this way the synthetic nature can be recognized.
Observing the effects of luminescence under extremely short uv can be very useful in recognizing synthetic diamonds.
Synthetic diamond producers claim that:
Lab-grown diamonds essentially have the same chemical composition, crystalline structure, optical and physical properties as diamonds extracted from mines: they are, therefore, 100% diamonds. The only difference between synthetic and mined diamonds is that one was created within the Earth and extracted while the other was created in a cutting-edge laboratory.
Numerous producers synthetize diamond above all for industrial purposes.
In jewellery, the size of multi-faceted gems has reached decidedly significant dimensions: gems of over 10 ct have been seen.
But the greatest distribution of this product is with gems up to a maximum of 2.00 ct and in melee lots (from less than a dot to up to 0.25 ct).
Constant growth and distribution of this gemmological material in the jewellery sector is towed by its intensive and ever-greater use in industry.
It is widely used in instruments such as super sanders, grinding wheels, cutting tools, tools for drilling and polishing, products used in the automobile, medical, aerospace and electronic industries.
Due to their manufacturing costs and market importance, synthetic diamonds play a leading role in Asian countries, followed by North America.
Commercially-speaking, they are receiving considerable success and distribution in the USA and Japan.
As a detrimental measure against those dealing in the natural stone, the American FTC (Federal Trade Commission, the legislative trade authority) has allowed these synthetic stones to be called “grown diamonds”.
It has also established that «synthetic diamond» is to be considered as real «diamond», thus allowing the synthetic stone producers to market their products as «real» / «true» diamonds.
The rest of the world and the international ISO standards foresee that, for the purposes of clarity and the consumers’ benefit, this gemmological material should only be called “synthetic diamond” the same as any other type of synthetic product.
No other definition or simplification is allowed.
The cost of this material is currently 30-40% lower than natural stone but further reductions are foreseen due to its ever-greater distribution and a reduction in production costs.
Synthetic diamonds currently represent about 2% of the global market.
It is expected that, by 2030, this share will have risen to 10%.
For stones that weigh around 0.50-1.50 ct, suitable to be used as solitaires, that is, for engagement rings, a 7.5% share could already be reached in 2020.
The share could reach 15% in the next two years for «melee».
The distribution of this material in melee could be intensified by a progressive scarcity of diamonds extracted from mines, since the Argyle mine, which currently supplies the majority of the world’s small diamonds, is soon to be closed (almost totally exhausted).
It is therefore difficult at this moment in time to predict exactly how this material will affect the jewellery market.
From marketing studies, it would seem that new generations are positively in favour of using this new material in personal ornamentation.
The diamond is losing its appeal as a symbol of rarity and eternal love and is becoming a highly common gem.
Consumers are beginning to see synthetic diamonds as desirable: they can have much larger gems at lower prices and, above all, make an investment «without feeling guilty».
Considerable media campaigns to publicize these gems as much more ‘ethical’ than their natural counterparts, are underway.
The younger generations, rightly oriented towards the environment and the non-exploitation of natural and, above all, human resources, are showing greater interest in this type of gem compared to past generations, who were more greatly concerned about the uniqueness and rarity of each jewellery item.
Big names from the entertainment and web worlds, such as Di Caprio, Lady Gaga, Penelope Cruz or the owners of Facebook, Twitter and eBay, have publicized or even financed synthetic diamond production facilities, believing in their future.
The Diamond Foundry, one of the latest US producers to appear on the market, has declared itself as the only producer currently supplying certified «carbon neutral» diamonds, since its stones are made in a hydroelectrically-powered plasma reactor.
The company claims that: “mine extraction has a greater impact on the environment than any other human activity. For every single carat of diamond mined, about 250 tons of earth must be excavated and this releases a considerable amount of atmospheric pollution with heavy carbon dioxide emissions."
Through its LIGHTBOX brand, De Beers has started the on-line sale of a line of colourless, blue and pink synthetic diamond jewellery at a much lower cost, trying to secure a significant share of the global market (1.00 ct 800.00 US$ - 0.50 ct 400.00 US$ - 0.25 ct 250.00 US$).
More than 60% of those interviewed in studies would be willing to buy, or interested in buying, a synthetic diamond for an engagement ring due to the lower cost of the material which would allow them to have a larger stone at a lower cost.
Consumers with financial resources, traditionally more bound to the charm and mysticism of the unique and unrepeatable … now seem to be showing a lot of interest in this material.
Synthetic diamond producers have been able to arouse the interest of the so-called «millennials» by promoting Lab Grown Diamonds as high-tech, innovative and clean.
In every aspect of their lives, Millennials look for brands, companies and products that they believe to be transparent, social and respectful of the environment.
Nowadays, consumers no longer believe in the value of diamonds or of jewellery in general.
In fact, several factors have spread mistrust in the sector over the years.
We must, however, bear in mind that: a natural diamond, even if poor in quality, will always have a potential buyer.
There is, on the other hand, no secondary market for synthetic diamonds, especially since diamond traders currently tend not to deal in them.
The «good bargain» aspect, or rather, the savings made on buying a synthetic diamond, becomes less tangible when you consider the fact that it will not be possible to re-sell it.
At the moment, the outlook is decidedly confusing and unclear.
World traders, given the economic interest that rotates around the natural material, are decidedly concerned and scared about the sudden distribution and by the number of media campaigns that feature synthetic diamond.
But, if we look at the past what is happening now was promoted in exactly the same way before when, at the beginning of the last century, DeBeers, through targeted media campaigns and movie stars (we could mention Marylin Monroe and phrases like «diamonds are a girl’s best friend» and «diamonds are forever»), disseminated the use of diamonds in jewellery so that they could become a «symbol of true and eternal love» for everyone.
It is therefore hard to answer the initial question but perhaps we could now pose another: “could synthetic diamond be an opportunity?”
Dr. Antonello Donini is responsible of CISGEM Gemologic Laboratory (Centro Informazioni e Servizi Gemmologici) with more than 30-year experience in gem analysis, with particular focus on diamonds.