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CVD vs HPHT Lab Grown Diamonds. What's the Difference? Which is better?

HPHT vs. CVD  
Why JANAI only chooses CVD Type IIA 

Channelling the beauty of nature and technological innovation, Lab-Grown Diamonds have revolutionised the Diamond Industry and forever changed the accessibility to fine diamond jewellery. Advances in technology have allowed laboratories to simulate the natural conditions deep within the earth's mantle to replicate the growing process of Natural Diamonds. This ambitious technique results in the creation a precious Diamond with the same chemical properties and carbon-structure as those formed naturally more than 1.6 billion years ago

A Lab-Grown Diamond is structurally, chemically and visually identical to a natural diamond. Lab Grown diamonds are real diamonds with the same range of cut, clarity, colour, and carat weight that you would associate with a mined diamond

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A Lab-Grown Diamond is developed using one of two different methods, High Pressure High Temperature (HPHT) or Chemical Vapor Deposition (CVD).

The HPHT method was the original way to produce man-made diamonds. First developed by General Electric in the 1950’s, the earliest man-made diamonds produced were tiny and heavily included (unfit for any kind of jewellery) and were purposed for industrial use. HPHT synthetic diamonds have greatly benefited the commercial industry for use in electronics, surgical tools, optics, and cutting tools. NASA commissioned HPHT diamonds for their satellites due to their density, hardness, thermal conductivity and their properties to withstand heat. The HPHT growing method is very expensive and energy consuming, the HPHT technique can now be considered an outdated technology.

The HPHT process begins with a graphite/metals seed that is placed within a HPHT chamber and is exposed to extreme temperatures of 1300-1600
°C and tremendous pressures of 50-60 kb. These are similar conditions that create natural diamond formations within the earth. A carbon starting material such as graphite alongside other metals are added to the chamber, which melt and crystalise, fusing themselves to the diamond seed to grow into a diamond rough. A HPHT diamond rough has 14 growth directions and grows into a cuboctahedron shape.

A HPHT diamond can display colour zoning and have a tendency to produce a faint yellow or brown hue. HPHT Diamonds exhibit metallic inclusions, which tend to be darker in appearance and can make them magnetic. This is one of the ways an independent geologist will decipher the stone's origins. These inclusions originate from graphite within the diamond from the growing process, and can also contain traces of iron, manganese, aluminum, nickel and cobalt that may fuse with the diamond within the chamber. The purity of the HPHT seed also accounts for these inclusions, as the DNA of a HPHT diamond seed is graphite, not pure carbon like a flawless Diamond.

Majority of the diamonds produced today using the HPHT method are not of gem quality and instead are used for industrial purposes in tools and equipment due to their high level of inclusions. They are typically smaller in carat weight than CVD diamonds. HPHT diamonds used in fine jewellery are not 'As Grown', instead they are 'As Created' and undergo heavy post-growth treatments to improve their low qualities in colour to greatly improve their appearance.  This post-growth treatment can enhance the diamond colour from yellow to colourless. All HPHT diamonds with a low clarity grade may break or crack during this heat treatment, causing wastage and unusable diamonds.

The CVD (Chemical Vapor Deposition) process is the modern and refined way of producing Lab-Grown Diamonds. CVD developed diamonds produce exceptional quality, colour and clarity stones and have come a long way since HPHT. The CVD (Chemical Vapor Deposition) method imitates how diamonds form in interstellar gas clouds in outer-space. This method uses less pressure compared to HPHT technique, smaller machines, and cultivates higher clarity diamonds. CVD diamonds are developed specifically to be beautiful diamonds fit for Engagement Rings and fine jewellery.

The CVD process begins with a high quality diamond seed (a thin slice of diamond) that is placed within a vacuum chamber and exposed to temperatures of around 700-1300°C. The CVD chamber then becomes filled with carbon rich gasses. This technique produces plasma and the release of carbon pieces within the chamber, which then rain down and bond to the diamond seed causing the diamond seed to grow into a diamond rough. A CVD diamond only has one growth direction and grows into a cubic shape. The size of a Lab-Grown Diamond can be controlled depending on the time allowed for growth. The largest recorded is a 30 carat Emerald Cut Lab-Grown named the “Pride of India” certified by IGI.

CVD Lab-Grown Diamonds can be produced colourless with no colour zoning and even distribution. CVD diamonds never contain metal inclusions, but may exhibit mineral inclusions as a result of their growth process. CVD Type IIA diamonds are sold ‘As-Grown’, meaning they have not undergone any post-growth treatment to improve their colour or clarity.

CVD Type IIA diamonds have set precedent for spectacular and high quality stones. Type IIA diamonds are the most chemically pure form of diamond due to the low amount of nitrogen, making them extremely hard and bright.  CVD (Chemical Vapor Deposition) diamonds are at the forefront of truly sustainable luxury for the modern and savvy consumer.

With the diamond market now attuned to the growing environmental and ethical concerns of the production of mining, ensuring the origins of a diamond is more important than ever. For the ultimate in ‘As Grown’ CVD (Chemical Vapor Deposition) diamonds, it is more common that these diamonds are fully traceable and climate neutral options for the environmentally and ethically conscious. The provenance can now be reliably traced back to its origins, ensuring ethical work practices and sustainable production. Alongside purchase with many CVD Lab-Grown Diamond will be an SCS certificate (SCS is a global services leader in independent environmental certification and standards development). And all Lab-Grown diamonds are third party certified, graded and inscribed by the world’s leading gemological laboratories.

For full transparency, the most reliable way to identify between HPHT and CVD diamonds is via a grading report defining the growing method. Reputable labs such as IGI, GCAL and GIA will indicate whether the diamond is HPHT, CVD and document any colour treatments to the stone.

At Janai we always provide exceptional quality stones, deliver beauty and source premium CVD Type IIA certified diamonds. Our diamond specialists can assist and educate you about choosing the perfect loose stone and bring your dream engagement ring to life.
Book your appointment with Janai to discover more about which stone is right for you.