Laboratory Grown Diamonds
We are delighted to announce that we now have in store a new range of jewellery set with beautiful laboratory grown diamonds! This article will aim to answer the following frequently asked questions about laboratory grown diamonds:
- Why do we want to grow diamonds in the laboratory?
- How are diamonds grown in the laboratory?
- Are laboratory grown diamonds different to those mined from the ground?
- Why might I want to choose a laboratory diamond rather than a mined diamond?
Why do we want to grow diamonds in the laboratory?
Around 3000 years ago in India, a twinkling pebble caught someone’s eye. Picking it up, they realised that, not only was it an object of beauty, but it was different from other stones. This pebble was a diamond crystal. Ever since that time, we have collected them, built legends around them, used them as tools, prized them as gems and more recently, given them as symbols of love.
Rough crystals and faceted mined diamonds
Photo credit: GIA
The desire to create diamonds goes back centuries. Experiments carried out in the 18th century paved the way for the discovery that diamonds are composed of carbon atoms. The discovery of the Kimberley deposits in South Africa in the late 1860s eventually led to the realisation that diamonds form deep in the Earth where the temperature and pressure are extremely high and are brought to the surface by a special and rare type of volcanic eruption. This fuelled some ingenious and frankly down-right dangerous attempts to produce diamonds in the laboratory, all of which proved unsuccessful.
Diagram showing where diamonds can form and how they are brought to the surface by rare kimberlite eruptions. The diamonds formed over long periods of time, millions, or even billions of years ago.
Picture Credit: R. Tappert and M. C. Tappert, “Diamonds in Nature: A Guide to Rough Diamonds”.
Early attempts to grow diamond in the laboratory were more out of scientific curiosity than necessity. A diamond’s unique combination of physical and optical properties makes it not only sought-after as a gem, but also lends it to many industrial and technological applications. World War II saw an increase in the use of diamonds within industry and technology. Consequently, the race to grow diamond in the laboratory had to accelerate and there was huge investment in research and development. It took until the 1950s for the first single crystal diamonds to be grown in the lab and they were exceedingly small and poor quality, but good enough for applications such as industrial grit in cutting tools.
During the years that followed, production techniques were refined to synthesise larger and better-quality crystals for both industrial and the growing number of technological applications. However, even though these could now be considered as “gem quality” they were not intended for the jewellery market. This all changed when the old Soviet Union began to crumble, and Russia entered a period of perestroika. Embracing aspects of capitalism, by the 1990s they wanted to make laboratory grown diamonds for use in jewellery and by the end of the 1990s, small quantities of Russian laboratory grown diamonds entered the market.
Since then, a steadily increasing number of companies have invested in developing and marketing laboratory grown diamonds for use in jewellery and they are now available in a variety of sizes, colours and high clarities.
Gem quality laboratory grown diamonds are now available in a variety of colours depending on growth conditions and post-growth treatments.
Photo credit: G&G Summer 2018, Vol. 54, No.2 pp. 202-204.
How are diamonds grown in the laboratory?
There are two growth methods:
- High Pressure High Temperature (HPHT)
- Chemical Vapour Deposition (CVD)
HPHT growth mimics the high temperature and pressure conditions in which a natural diamond forms. The temperatures used are around 1300 – 16000C and the pressure around 50 – 60 kbar (imagine 80 elephants standing on your toe)! However, to generate these high temperatures and pressures in the laboratory requires specialist equipment and the addition of a metal catalyst to reduce the kinetic barrier and act as a transport media for dissolved carbon. Highly refined graphite or pure diamond powder are added to a reaction cell as a source of carbon. Inside the reaction cell, the carbon source melts and dissolves into the metallic flux. At the bottom of the reaction cell is a diamond seed crystal and as this area of the reaction cell is at a slightly lower temperature than the top, a convection current brings the dissolved carbon down to the seed where it can crystallise and so the diamond grows. It takes about 1 – 2 weeks to grow a 2 carat diamond using the HPHT method.
Diagram of the HPHT reaction cell. This is loaded into a press where extremely high pressures and temperatures are generated.
Diamond crystals grown by the HPHT method
Photo credit: Gems and Gemology, Vol. 53, No. 3. Pp.262-284.,
CVD growth is quite different, and this is the method used for the laboratory grown diamonds we have in stock. Methane gas is used as a source of carbon and together with hydrogen gas is added to the reaction chamber under vacuum conditions. At the bottom of the reaction chamber there are diamond seed plates. Microwaves are used to heat the gases to around 9000C where they become a plasma and carbon atoms rain down onto the cooler seed plates where they precipitate to form growing diamond crystals. As in HPHT growth, it takes about 1 to 2 weeks to produce a 2 carat crystal.
Diagram of the CVD apparatus. Inside the reaction chamber the plasma ball and diamond seed plates can be seen.
Rough CVD diamond crystal (left), with the amorphous carbon overgrowth lasered off (centre), faceted (right).
Photo credit: Gems and Gemology, Vol. 52, No. 3 pp.222-245.
Are laboratory grown diamonds different to diamonds mined from the ground?
Laboratory grown diamonds have the same chemical composition and crystal structure as a diamond mined from the ground, giving them the same physical and optical properties. As the hardest known mineral, a diamond will retain its exceptional polish and adamantine lustre for years, making it the ideal gemstone for a lifetime of wear, such as an engagement ring. Carefully placed facets ensure that the diamond will give maximum brilliance (return of light to the eye) and fire (flashes of spectral colour) for unrivalled beauty.
As laboratory grown diamonds look the same as a mined diamond, this has led to some concerns that the public may be deceived into buying a laboratory grown diamond believing it has been mined. We sell jewellery containing laboratory grown diamonds with full disclosure and the larger sizes are supplied with a full Laboratory Grown Diamond Report from the International Gemological Institute giving details of the grading results for carat, colour, clarity and cut.
One way to tell if a diamond has been grown in a laboratory is to look (under magnification) on the girdle for a laser inscription disclosing this origin:
An example of a laser inscription on the girdle of a laboratory grown diamond.
Photo credit: Gems and Gemology, Vol. 52, No. 3 pp.222-245.
The only differences between laboratory grown and mined diamonds are due to their different growth origins. For example, if a diamond contains inclusions it may give you clues as to its origin. HPHT grown diamonds may contain metallic inclusions originating from the flux in which they grew:
Rod shaped metallic flux inclusions in an HPHT grown diamond, seen under magnification.
Photo credit: Gems and Gemology, Vol. 53, No.3. pp.262-284.
CVD grown diamonds may contain graphite inclusions, but these look really similar to the black sulphide mineral inclusions found in many mined diamonds, so are not diagnostic:
Tiny amorphous carbon or graphite inclusions in a CVD diamond, seen under magnification.
If a diamond has not been laser inscribed and is suspected to be laboratory grown, then the only way to confirm its origin is to send it away for advanced testing in a gemmological laboratory.
At the gemmological laboratory, a variety of tests will be carried out to confirm the diamond’s origin. For example, the IIDGR DiamondView can be used on stones from 0.05 to 10 carats. It uses very short-wave ultraviolet radiation to look at the fluorescence colours and patterns of the different growth zones in the diamond as differences in their growth environments reveal different growth patterns:
IIDGR DiamondView fluorescence images under magnification: Left = majority of mined diamonds fluoresce blue with this growth pattern; centre = typical pattern for an HPHT grown diamond; right = typical pattern for a CVD diamond.
Photo credit: Left and centre = Laboratory-Grown Diamonds: Updates and Identification | GIA Knowledge Sessions Webinar Series – YouTube, right = Gems and Gemology, Vol. 52, No. 3, pp.222-245.)
Why might I want to choose a laboratory diamond rather than a mined diamond?
Interest and awareness in laboratory grown diamonds has increased tremendously over the past few years.
Some people chose lab grown diamonds for environmental reasons. At this time, although several reports have been published, there are no independently prepared, reliable data comparing the carbon footprint of laboratory grown and mined diamonds. However, we can see that diamond mining can create holes so big that they can be seen from space and people are worried about habitat destruction (although all major mines must now have restoration and regeneration plans in place for when the mine reaches the end of its working life).
The Diavik mine in Canada’s Northwest Territories
Photo Credit: Gems and Gemology, Vol. 52, No.2 pp. 104-131.
Many have heard of “blood diamonds” or “conflict diamonds”. Conflict diamonds are defined as rough diamonds used by rebel movements or their allies to finance armed conflicts aimed at undermining legitimate governments. Furthermore, these rebels made use of forced and child labour to mine their diamonds. In 2003, the Kimberley Process came into effect, aiming to prevent conflict diamonds from entering the market, whilst protecting legitimate trade in rough diamonds. Thanks to the Kimberley Process, today 99.8% of mined diamonds traded are conflict free. However, a laboratory grown diamond is guaranteed to be conflict free.
Photo credit: Global Witness Central African Republic: An inside look into the social media world of diamond smuggling | Global Witness
Finally, even though a laboratory grown diamond is just as durable and beautiful as a mined diamond, jewellery containing laboratory grown diamonds will cost around half the price of a similar piece containing mined diamonds!