JEWELRY EDUCATION
Lab Grown Diamond Formation: HPHT vs CVD
Lab-grown diamonds are chemically, physically, and optically the same as their natural counterparts. The only difference here, is their origin.
Instead of being formed over billions of years deep inside the Earth’s crust, lab-grown diamonds are created in high-tech laboratories. Using advanced methods, modern-day technology has created a way to replicate the natural conditions that are needed for diamond growth.
In this guide, we’ll explore the two main methods used to create lab-grown diamonds—High Pressure High Temperature (HPHT) and Chemical Vapor Deposition (CVD)—and how each process shapes the final stone.
Understanding the difference between HPHT and CVD can help you appreciate how your diamond was formed and what to expect in terms of characteristics, availability, and overall quality.
How Lab-Grown Diamonds Are Made
To produce a lab-grown diamond, scientists begin with a diamond “seed”. The seed is a thin slice of a natural or synthetic diamond, and is placed into a controlled growth environment where carbon atoms attach to it and crystallize, eventually forming a full-sized diamond.
While the end result is a real diamond, the conditions that create it differ significantly depending on the method used.
The two dominant techniques are HPHT and CVD, both of which have their own set of advantages and challenges.
HPHT Diamonds
The High Pressure High Temperature (HPHT) process mimics the natural geological forces that form diamonds deep underground. This technology was first developed in the 1950s; it’s a method that uses a press to generate extreme pressure (around 5–6 GPa) and temperatures (1,300–1,600°C) to force carbon into a crystalline diamond structure.
There are three kinds of presses that can be used in the HPHT process —belt, cubic, and split-sphere (BARS). Each press is capable of producing gem-quality diamonds in a matter of days to weeks. HPHT is particularly effective at creating diamonds with a high degree of clarity and color; that is, less inclusions with a lesser brown hue.
CVD Diamonds
Chemical Vapor Deposition (CVD) is a more recent technology. It still makes use of a diamond seed to start the growth process, but it differs in that it allows diamonds to grow in a vacuum chamber from a hydrocarbon gas mixture, which is typically methane.
Unlike HPHT, CVD operates under lower pressures but still uses high temperatures (around 800–1,200°C).
In this method, carbon atoms are separated from the gas and gradually accumulate layer by layer on the diamond seed.
Over time, this results in a high-purity diamond with a tabular or cube-shaped crystal form. Because CVD allows for more precise control over growth conditions, it’s especially suited for creating diamonds with fewer metallic inclusions and high optical clarity.
CVD diamonds can sometimes display a brown or gray tint right after growth, but these colors are often removed through a treatment that’s typically used in the HPHT method – an important note: many diamonds on the market are grown through a combination of both methods.
What’s More Common Today?
While HPHT was the first technique developed for growing diamonds, CVD has become the dominant method in the industry today.
The reason being: it’s scalable, energy efficient, and gives a greater level of control over a diamond’s purity and growth.
That said, HPHT still plays an important role—not only in growing diamonds, but also in enhancing them. Many CVD diamonds undergo HPHT post-treatments to improve their color or remove internal strain.
Conclusion
To the naked eye, you won’t be able to tell whether a diamond was created using HPHT or CVD. Gemological laboratories, however, can distinguish between the two using advanced testing equipment that reveals differences in fluorescence patterns, inclusion types, and trace elements.
With this in mind, lab-grown diamonds are at the cutting edge of modern tech, and offer a cost-effective and sustainable alternative to mined diamonds. Whether they’re created through HPHT or CVD, lab-grown diamonds have all the beauty and brilliance of their natural counterparts.
If you’re in the market for a lab-grown diamond piece, we warmly invite you to our showroom in Chestnut Hill for a complimentary consultation. We’ve been serving the area for over 30 years, and through our world-class service and expertise, have become a name that’s associated with boutique, one-of-a-kind jewelry in the Greater Boston Area.
